Article

Consequences of elevated carbon dioxide and ozone for foliar chemical composition and dynamics in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera)

February 2001
Environmental Pollution 115(3):395-404

February 2001
115(3):395-404

DOI:10.1016/S0269-7491(01)00229-9

Source
PubMed

Authors:

Richard L. Lindroth

University of Wisconsin–Madison

Brian J. Kopper

Animal and Plant Health Inspection Service

William F. J. Parsons

Bishop's University

James Bockheim

University of Wisconsin–Madison

Show all 9 authorsHide

Atmospheric chemical composition affects foliar chemical composition, which in turn influences the dynamics of both herbivory and decomposition in ecosystems. We assessed the independent and interactive effects of CO2 and O3 fumigation on foliar chemistry of quaking aspen (Populus tremuloides) and paper birch (Betula papyrifera) at a Free-Air CO2 Enrichment (FACE) facility in northern Wisconsin. Leaf samples were collected at five time periods during a single growing season, and analyzed for nitrogen, starch and condensed tannin concentrations, nitrogen resorption efficiencies (NREs), and C:N ratios. Enriched CO2 reduced foliar nitrogen concentrations in aspen and birch; O3 only marginally reduced nitrogen concentrations. NREs were unaffected by pollution treatment in aspen, declined with O3 exposure in birch, and this decline was ameliorated by enriched CO2. C:N ratios of abscised leaves increased in response to enriched CO2 in both tree species. O3 did not significantly alter C:N ratios in aspen, although values tended to be higher in +CO2+O3 leaves. For birch, O3 decreased C:N ratios under ambient CO2 and increased C:N ratios under elevated CO2. Thus, under the combined pollutants, the C:N ratios of both aspen and birch leaves were elevated above the averaged responses to the individual and independent trace gas treatments. Starch concentrations were largely unresponsive to CO2 and O3 treatments in aspen, but increased in response to elevated CO2 in birch. Levels of condensed tannins were negligibly affected by CO2 and O3 treatments in aspen, but increased in response to enriched CO2 in birch. Results from this work suggest that changes in foliar chemical composition elicited by enriched CO2 are likely to impact herbivory and decomposition, whereas the effects of O3 are likely to be minor, except in cases where they influence plant response to CO2.

Ozone Pollution: Impacts on ecosystem services and biodiversity

Technical Report

Full-text available

Apr 2013

In this report we provide a review of the state of current knowledge on the effects of ozone pollution on ecosystem services including consideration of effects on biodiversity. Although considered separately, all of the ecosystem services and underlying processes are interlinked, with for example, ozone impacts on root growth contributing to supporting services (primary productivity), provisioning (crop and timber production), regulating (C sequestration and impacts on climate) and cultural services (reduced growth of sensitive species influencing aesthetic qualities of vegetation), and reducing economic value of products such as crop yield. Until recently, much of the research on ozone impacts has focussed on quantifying effects on ecological processes rather than considering the implications for ecosystem services. This report, for the first time, places current process-based knowledge within the context of ecosystem services and thus reports on the potential for impacts of ozone on ecosystem services and biodiversity. The report has been prepared by the Coordination Centre of the ICP Vegetation, an International Cooperative Programme reporting on air pollution impacts on vegetation to the Working Group on Effects of the Convention on Long-Range Transboundary Air Pollution.

The effects of elevated ozone and CO2 on growth and defense of native, exotic and invader trees

Article

Full-text available

Dec 2016

Aims: Elevated ozone and CO2 can differentially affect the performance of plant species. Variation among native, exotic, and invader species in their growth and defense responses to CO2 and ozone may shape CO2 and ozone effects on invasions, perhaps in part also due to variation between native and invasive populations of invaders. Methods: We manipulated ozone (control or 100 ppb) and CO2 (ambient or 800 ppm) in a factorial greenhouse experiment in replicated chambers. We investigated growth and defense (tannins) of seedlings of Triadica sebifera from invasive (US) and native (China) populations and pairs of US and China tree species within three genera (Celtis, Liquidambar, Platanus). Important findings: Overall, ozone reduced growth in ambient CO2 but elevated CO2 limited this effect. Triadica sebifera plants from invasive populations had higher growth than those from native populations in control conditions or the combination of elevated CO2 and ozone in which invasive populations had greater increases in growth. Their performances were similar in elevated CO2 because native populations were more responsive and their performances were similar with elevated ozone because invasive populations were more susceptible. Compared to other species, T. sebifera had high growth rates but low levels of tannin production that were insensitive to variation in CO2 or ozone. Both China and US Platanus plants reduced tannins with increased CO2 and/or ozone and US Liquidambar plants increased tannins with the combination of elevated CO2 and ozone. The growth results suggest that intraspecific variation in T. sebifera will reduce the effects of CO2 or ozone alone on invasions but increase their combined effects. The tannin results suggest that defense responses to CO2 and ozone will be variable across native and exotic species. The effects of CO2 and ozone on growth and defense of native and exotic species indicate that the benefit or harm to species from these global change drivers is an idiosyncratic combination of species origin and genus.

Effects of elevated concentrations of atmospheric CO2 and tropospheric O-3 on leaf litter production and chemistry in trembling aspen and paper birch communities

Article

Full-text available

Dec 2005

Human activities are increasing the concentrations of atmospheric carbon dioxide ([CO2]) and tropospheric ozone ([O-3]), potentially leading to changes in the quantity and chemical quality of leaf litter inputs to forest soils. Because the quality and quantity of labile and recalcitrant carbon (C) compounds influence forest productivity through changes in soil organic matter content, characterizing changes in leaf litter in response to environmental change is critical to understanding the effects of global change on forests. We assessed the independent and combined effects of elevated [CO2] and elevated [O-3] on foliar litter production and chemistry in aspen (Populus tremuloides Michx.) and birch-(Betula papyrifera Marsh.) aspen communities at the Aspen free-air CO2 enrichment (FACE) experiment in Rhinelander, WI. Litter was analyzed for concentrations of C, nitrogen (N), soluble sugars, lipids, lignin, cellulose, hemicellulose and C-based defensive compounds (soluble phenolics and condensed tannins). Concentrations of these chemical compounds in naturally senesced litter were similar in aspen and birch-aspen communities among treatments, except for N, the C:N ratio and lipids. Elevated [CO2] significantly increased C:N (+8.7%), lowered mean litter N concentration (-10.7%) but had no effect on the concentrations of soluble sugars, soluble phenolics and condensed tannins. Elevated [CO2] significantly increased litter biomass production (+33.3%), resulting in significant increases in fluxes of N, soluble sugars, soluble phenolics and condensed tannins to the soil. Elevated [O-3] significantly increased litter concentrations of soluble sugars (+78.1%), soluble phenolics (+53.1%) and condensed tannins (+77.2%). There were no significant effects of elevated [CO2] or elevated [O-3] on the concentrations of individual C structural carbohydrates (cellulose, hemicellulose and lignin). Elevated [CO2] significantly increased cellulose (+37.4%) input to soil, whereas elevated [O-3] significantly reduced hemicellulose and lignin inputs to soil (-22.3 and -31.5%, respectively). The small changes in litter chemistry in response to elevated [CO2] and tropospheric [O-3] that we observed, combined with changes in litter biomass production, could significantly alter the inputs of N, soluble sugars, condensed tannins, soluble phenolics, cellulose and lignin to forest soils in the future.

Effects of Elevated Atmospheric Carbon Dioxide and Tropospheric Ozone on Phytochemical Composition of Trembling Aspen ( Populus tremuloides ) and Paper Birch ( Betula papyrifera )

Article

Full-text available

Jan 2017
J CHEM ECOL

Anthropogenic activities are altering levels of atmospheric carbon dioxide (CO2) and tropospheric ozone (O3). These changes can alter phytochemistry, and in turn, influence ecosystem processes. We assessed the individual and combined effects of elevated CO2 and O3 on the phytochemical composition of two tree species common to early successional, northern temperate forests. Trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) were grown at the Aspen FACE (Free-Air Carbon dioxide and ozone Enrichment) facility under four combinations of ambient and elevated CO2 and O3. We measured, over three years (2006–08), the effects of CO2 and O3 on a suite of foliar traits known to influence forest functioning. Elevated CO2 had minimal effect on foliar nitrogen and carbohydrate levels in either tree species, and increased synthesis of condensed tannins and fiber in aspen, but not birch. Elevated O3 decreased nitrogen levels in both tree species and increased production of sugar, condensed tannins, fiber, and lignin in aspen, but not birch. The magnitude of responses to elevated CO2 and O3 varied seasonally for both tree species. When co-occurring, CO2 offset most of the changes in foliar chemistry expressed under elevated O3 alone. Our results suggest that levels of CO2 and O3 predicted for the mid-twenty-first century will alter the foliar chemistry of northern temperate forests with likely consequences for forest community and ecosystem dynamics.

Effects of elevated ozone on growth and foliar traits of European and hybrid aspen

Article

Apr 2009
BOREAL ENVIRON RES

We studied growth and foliar responses of two clones of both European aspen (Populustremula) and hybrid aspen (P. tremula × P. tremuloides) to elevated O3 (45 ppb, 14-h mean) over one growing season using a free-air fumigation system in central Finland. All clones exhibited O3-specific foliar injury and accelerated leaf senescence under elevated O3. Yet, exposure to 1.5 × ambient O3 had only minor effects on the growth and biomass production of clones grown under optimal nutrient and water supply, and no O3 effects on leaf morphology were observed. Slower-growing European aspen was more sensitive to elevated O3 than hybrid aspen. Exposure to O3 decreased the root/stem ratio (-11%) and leaf N concentration (-9%) of European aspen. Inter- or intraspecific differences in the O3 sensitivity of the trees could not be explained by stomatal conductance, but some xeromorphic leaf traits were related to increased susceptibility to O3. Intraspecific differences in the O3 sensitivity have implications e.g. for nurseries producing commercial tree material.

European aspen and hybrid aspen under changing environment – Leaf traits, growth and litter decomposition

Article

Full-text available

Jan 2011

Suvi Nikula

Secondary metabolites responses of plants exposed to ozone: an update

Article

Full-text available

Jul 2023
ENVIRON SCI POLLUT R

Tropospheric ozone (O3) is a secondary pollutant that causes oxidative stress in plants due to the generation of excess reactive oxygen species (ROS). Phenylpropanoid metabolism is induced as a usual response to stress in plants, and induction of key enzyme activities and accumulation of secondary metabolites occur, upon O3 exposure to provide resistance or tolerance. The phenylpropanoid, isoprenoid, and alkaloid pathways are the major secondary metabolic pathways from which plant defense metabolites emerge. Chronic exposure to O3 significantly accelerates the direction of carbon flows toward secondary metabolic pathways, resulting in a resource shift in favor of the synthesis of secondary products. Furthermore, since different cellular compartments have different levels of ROS sensitivity and metabolite sets, intracellular compartmentation of secondary antioxidative metabolites may play a role in O3-induced ROS detoxification. Plants’ responses to resource partitioning often result in a trade-off between growth and defense under O3 stress. These metabolic adjustments help the plants to cope with the stress as well as for achieving new homeostasis. In this review, we discuss secondary metabolic pathways in response to O3 in plant species including crops, trees, and medicinal plants; and how the presence of this stressor affects their role as ROS scavengers and structural defense. Furthermore, we discussed how O3 affects key physiological traits in plants, foliar chemistry, and volatile emission, which affects plant–plant competition (allelopathy), and plant–insect interactions, along with an emphasis on soil dynamics, which affect the composition of soil communities via changing root exudation, litter decomposition, and other related processes.

Secondary metabolites responses of plants exposed to ozone: an update

Article

Jul 2023

Effects of elevated ozone on the uptake and allocation of macronutrients in poplar saplings above- and belowground

Article

Aug 2022
SCI TOTAL ENVIRON

Ground-level ozone (O3) is a secondary air pollutant and affects the roots and soil processes of trees. Therefore, O3 can affect the uptake and allocation of nutrients in trees, which merits further clarification. A fumigation experiment with five O3 levels was conducted in 15 open top chambers for two poplar clones, and the concentrations of six macronutrients (N, P, K, S, Ca, Mg) in different organs and leaf positions were determined. Under all O3 levels, the concentration of mobile nutrients (N and P) was higher in upper leaves than in lower leaves, while the non-mobile nutrients (Ca and S) concentration was the opposite. Relative to charcoal filtered ambient air (CF), high O3 treatment (NF60) significantly increased the concentration of mobile nutrients K and Mg in upper leaves by 38 % and 33 %, in lower leaves by 142 % and 65 %, respectively, which suggested the effect of O3 on their concentrations was greater at the lower leaf position than at the upper leaf position. Elevated O3 significantly increased the macronutrient concentrations in most organs. The effects of O3 on nutrient concentrations were attributed using graphical vector analysis, suggested that the increase of nutrient concentration in the shoots was attributed to excessive nutrient stocks, while their increase in root was attributed to the “concentration” effect. Compared to CF, NF60 also reduced the root-to-shoot ratio of N, P, S, K, Ca and Mg stocks by 34 %, 39 %, 37 %, 64 %, 46 % and 42 %, respectively, indicating the allocation of increased nutrients to shoots in response to O3 stress. Changes in the allocation pattern of nutrients in different leaf positions and organs of poplar were primarily in response to O3 stress since these nutrients play important roles in some physiological processes. These results will help improve the plantation nutrient utilization by optimizing fertilizer management regimes under O3 pollution.

Mycorrhizal symbiosis and water condition affect ozone sensitivity of Medicago sativa L. by mediating stomatal conductance

Article

Aug 2022
ENVIRON EXP BOT

Ground level ozone (O3) pollution is a common environmental stress for plants in many regions of the world, while plant O3 sensitivity is largely influenced by plant water status. Arbuscular mycorrhizal (AM) fungi can form symbiosis with most terrestrial plants and play important role in plant resistance to various environmental stresses. However, how AM symbiosis and water conditions affect plant O3 sensitivity and the underlying mechanism remain unclear. In this study, alfalfa (Medicago sativa L.) was used as test plant, and the effects of AM inoculation and water conditions on plant growth and stress physiology under O3 enrichment were investigated. The results showed that O3 enrichment inhibited plant growth and caused visible injury on plant leaves. Water deficiency also caused significant decrease in plant biomass, while AM symbiosis promoted plant growth regardless of water condition and O3 enrichment. In general, water deficiency decreased while AM symbiosis increased plant O3 sensitivity. Nevertheless, under severe water deficiency, AM inoculation promoted plant growth without increasing plant O3 sensitivity. Water deficiency increased antioxidant enzyme activities and decreased stomatal conductance, while AM symbiosis increased both antioxidant enzyme activities and stomatal conductance. A significant negative correlation between stomatal conductance and O3 effect on plant total biomass supported that both water condition and AM symbiosis affect O3 sensitivity mainly through mediating stomatal conductance. However, AM symbiosis and water condition may differ in regulation mechanisms for stomatal conductance, as AM colonization significantly increased stomatal density, while water deficiency decreased stomatal aperture. Our study suggested that AM inoculation in combination with proper water management could largely mitigate the negative effects of O3 on plants.

Functional traits of poplar leaves and fine roots responses to ozone pollution under soil nitrogen addition

Article

Jun 2021
J ENVIRON SCI-CHINA

Concurrent ground-level ozone (O3) pollution and anthropogenic nitrogen (N) deposition can markedly influence dynamics and productivity in forests. Most studies evaluating the functional traits responses of rapid-turnover organs to O3 have specifically examined leaves, despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems. How elevated O3 levels impact fine root biomass and biochemistry remains to be resolved. This study was to assess poplar leaf and fine root biomass and biochemistry responses to five different levels of O3 pollution, while additionally examining whether four levels of soil N supplementation were sufficient to alter the impact of O3 on these two organs. Elevated O3 resulted in a more substantial reduction in fine root biomass than leaf biomass; relative to leaves, more biochemically-resistant components were present within fine root litter, which contained high concentrations of lignin, condensed tannins, and elevated C:N and lignin: N ratios that were associated with slower rates of litter decomposition. In contrast, leaves contained more labile components, including nonstructural carbohydrates and N, as well as a higher N:P ratio. Elevated O3 significantly reduced labile components and increased biochemically-resistant components in leaves, whereas they had minimal impact on fine root biochemistry. This suggests that O3 pollution has the potential to delay leaf litter decomposition and associated nutrient cycling. N addition largely failed to affect the impact of elevated O3 levels on leaves or fine root chemistry, suggesting that soil N supplementation is not a suitable approach to combating the impact of O3 pollution on key functional traits of poplars. These results indicate that the significant differences in the responses of leaves and fine roots to O3 pollution will result in marked changes in the relative belowground roles of these two litter sources within forest ecosystems, and such changes will independently of nitrogen load.

European aspen with high compared to low constitutive tannin defenses grow taller in response to anthropogenic nitrogen enrichment

Article

Feb 2021
FOREST ECOL MANAG

Boreal forests receive nitrogen-(N)-enrichment via atmospheric deposition and industrial fertilization. While it is known that N-enrichment can intensify interactions with natural antagonists, it remains poorly understood how genetic variability in plant defense chemistry can affect biotic interactions and height growth in N-enriched environments. We grew replicates of five low- and high-tannin Populus tremula genotypes, respectively, under three N-treatments (ambient, 15, and 150 kg N ha⁻¹ yr⁻¹). We assessed shoot blight occurrence (i.e. symptoms caused by Venturia fungi) during four growing seasons, and tree height growth during the same period. Damage by Venturia spp. increased with N-addition during all years, likely due to enhanced foliar quality. Low–tannin plants showed higher incidences of Venturia infection than high-tannin plants, regardless of the N-input-level. Height responded to an N-by-tannin-group interaction, which occurred because high-tannin plants grew taller than low-tannin plants at the high N-treatment, but not under the other N-levels. This pattern indicates that innate resource investment into tannin production yields a positive effect on growth under N-enriched conditions. Given that N-deposition is increasing globally, our research suggests that further studies are needed to investigate how N-enrichment interacts with plant defense traits globally. Moreover, our research suggests that N-deposition may provide an advantage for well-defended, high-tannin plants; and further, that genetic diversity in plant defense may be a key mechanism by which plant populations respond to this change.

Monitoring Ozone Effects on Vegetation: A Review

Article

Full-text available

Sep 2019

One of the most phytotoxic air pollutants is ozone, which can cause considerable damage to vegetation: visible leaf injury, reduction in yield quantity and quality and reduction in photosynthesis, alterations to carbon allocation, and in the sensitivity to biotic and abiotic stresses. Ozone is a secondary pollutant and prevailed at high concentrations over rural regions. Moreover, ozone concentrations are expected to increase in the future and will continue to be a serious threat to crop productivity. This paper presents a comprehensive review the undertaken studies of ozone's impacts on crops and natural ecosystems.

Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

Article

Full-text available

Aug 2020

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100. This is an open-access publication and can be downloaded at now cost: https://advances.sciencemag.org/content/6/33/eabc1176

Variations in foliar carbon:nitrogen and nitrogen:phosphorus ratios under global change: a meta-analysis of experimental field studies

Article

Full-text available

Jul 2020

Foliar-level stoichiometry plays an important role in ecosystem elemental cycling. Shifts in foliar ratios of carbon to nitrogen (C:N) and nitrogen to phosphorus (N:P) in response to global change can therefore have a large impact upon ecosystem function. We conducted a meta-analysis with 2,236 paired observations from 123 published studies to investigate the responses of foliar C:N and N:P ratios to experimental global change treatments, i.e. warming, increased precipitation, drought, N addition and elevated carbon dioxide concentration (eCO2), in field conditions. Foliar C:N and N:P ratios were neither affected by warming nor by increased precipitation. Foliar C:N ratio increased with drought and eCO2, and decreased with N addition. Foliar N:P ratios declined with eCO2, and increased under drought and N addition. Our results suggested the responses of the C:N ratio to global change were mainly related to shifts in foliar [N], whereas changes in the N:P ratio were related to the responses of both [N] and [P]. Moreover, the response magnitude of foliar N:P ratio decreased with treatment duration under increased precipitation, N addition and eCO2. Our findings are important for our understanding of plant nutrient dynamic and modeling of nutrient biogeochemistry under global change.

Effects of Elevated CO2 on SOC Pools under Resource Conservation in a Rice-Wheat System of IGP

Article

Full-text available

Aug 2014

Ozone effects on plants in natural ecosystems

Article

Full-text available

Feb 2019

Tropospheric ozone (O3) is an important stressor in natural ecosystems, with well‐documented impacts on soils, biota, and ecological processes. The effects of O3 on individual plants and processes scale up through the ecosystem through effects on carbon, nutrient, and hydrologic dynamics. Ozone effects on individual species and their associated microflora and fauna cascade through the ecosystem to the landscape level. Systematic injury surveys demonstrate that foliar injury occurs on sensitive species throughout the globe. However, deleterious impacts on plant carbon, water, and nutrient balance can also occur without visible injury. Because sensitivity to O3 may follow coarse physiognomic plant classes (in general, herbaceous crops are more sensitive than deciduous woody plants, grasses, and conifers), the task still remains to use stomatal O3 uptake to assess class and species’ sensitivity. Investigations of the radial growth of mature trees, in combination with data from many controlled studies with seedlings, suggest that ambient O3 reduces growth of mature trees in some locations. Models based on tree physiology and forest stand dynamics suggest that modest effects of O3 on growth may accumulate over time, other stresses (prolonged drought, excess nitrogen deposition) may exacerbate the direct effects of O3 on tree growth, and competitive interactions among species may be altered. Ozone exposure over decades may be altering the species composition of forests currently, and as fossil fuel combustion products generate more O3 than deteriorates in the atmosphere, into the future as well. This article is protected by copyright. All rights reserved.

Elevated ozone reduced leaf nitrogen allocation to photosynthesis in poplar

Article

Dec 2018
SCI TOTAL ENVIRON

We investigated the effects of elevated ozone (O3) concentration on leaf nitrogen (N), a key determinant of plant photosynthesis, with two clones of poplar grown in open-top chambers. We focus on the difference between mass-based leaf N concentration (Nmass) and area-based one (Narea) in their responses to elevated O3, and the allocation of N to different leaf components: photosynthetic apparatus, cell walls, and others under elevated O3 level. Our results showed that elevated O3 significantly increased Nmass, but reduced Narea and leaf mass per area (LMA). The two clones showed no difference in Nmass response to O3, but the more sensitive clone showed greater reduction of Narea and LMA due to O3. We also found positive relationships between Narea and photosynthetic parameters, e.g. light-saturated photosynthetic rate (Asat). Furthermore, elevated O3 significantly reduced photosynthetic N-use efficiency (PNUE) and leaf N allocation to photosynthetic components, while increasing N allocation to cell walls and other components. We concluded that plants invested more N in cell walls and other components to resist O3 damages at the expense of photosynthetic N. The change of N allocation in plant leaves in response to elevated O3 could have an impact on ecological processes, e.g. leaf litter decomposition.

Study of a Natural Leguminous Plants/Cork Oak Association in Kroumirie: An Alternative Solution to Climate Change

Article

Full-text available

Jan 2018

Despite the increase of the atmospheric CO2, cork oak (Quercus suber L.) forests don’t stop degenerating. Deficits in water balance and in nutritional elements might be the main raisons. Standing as a potential regulator of the ecosystem nutrient dynamics, leguminous plants (Fabaceae, Leguminosae) are a good test case for individual species effects on Tunisian forests. They are the most diverse and widespread group of plants with the capacity of N2 fixation, and are particularly abundant in Kroumiri forests. The use of natural legume species in Kroumirie, as soil fertility and grassland productivity enhancer, could be very interesting in the assessment of a new national land exploitation strategy aiming to increase carbon sequestration and climate change mitigation. Understanding the impact of these legume species on cork oak, using air nitrogen-fixation technique computation, would be crucial for future land management and policy decisions. A morphological and eco-physiological study of the Cytisus triflorus plant associated with Cork oak was carried out in Tabbouba, at Nefza region. Three sites were selected: CM1 (Cytisus triflorus alone), CM2 (Cork oak associated with Cytisus triflorus) and CM3 (Cork oak only). Morphological (height, diameter, density), physiological (stomatal conductance, water potential, transpiration, photosynthesis) and hydric parameters were measured for the two species. The morphological study results showed no significant difference sites for each species except for density parameter. On the other hand, physiological parameters measured for oaks trees clearly manifested significant differences in photosynthesis, transpiration and hydric conductance between CM2 and CM3 sites. The cork oak in association with the Cytisus are in better growth and productivity conditions than when they are alone.

Influence of elevated CO 2 on development and food utilization of armyworm Mythimna separata fed on transgenic Bt maize infected by nitrogen-fixing bacteria

Article

Full-text available

Jul 2018

Background Bt crops will face a new ecological risk of reduced effectiveness against target-insect pests owing to the general decrease in exogenous-toxin content in Bt crops grown under elevated carbon dioxide (CO 2 ). The method chosen to deal with this issue may affect the sustainability of transgenic crops as an effective pest management tool, especially under future atmospheric CO 2 level raising. Methods In this study, rhizobacterias, as being one potential biological regulator to enhance nitrogen utilization efficiency of crops, was selected and the effects of Bt maize (Line IE09S034 with Cry1Ie vs. its parental line of non- Bt maize Xianyu 335) infected by Azospirillum brasilense (AB) and Azotobacter chroococcum (AC) on the development and food utilization of the target Mythimna separate under ambient and double-ambient CO 2 in open-top chambers from 2016 to 2017. Results The results indicated that rhizobacteria infection significantly increased the larval life-span, pupal duration, relative consumption rate and approximate digestibility of M. separata , and significantly decreased the pupation rate, pupal weight, adult longevity, fecundity, relative growth rate, efficiency of conversion of digested food and efficiency of conversion of ingested food of M. separata fed on Bt maize, while here were opposite trends in development and food utilization of M. separata fed on non- Bt maize infected with AB and AC compared with the control buffer in 2016 and 2017 regardless of CO 2 level. Discussion Simultaneously, elevated CO 2 and Bt maize both had negative influence on the development and food utilization of M. separata . Presumably, CO 2 concentration arising in future significantly can increase their intake of food and harm to maize crop; however, Bt maize infected with rhizobacterias can reduce the field hazards from M. separata and the application of rhizobacteria infection can enhance the resistance of Bt maize against target lepidoptera pests especially under elevated CO 2 .

Negligible impacts of biomass removal on Douglas-fir growth 29 years after outplanting in the northern Rocky Mountains

Article

Jan 2018
BIOMASS BIOENERG

To investigate the long-term impacts of biomass harvesting on site productivity, we remeasured trees in the 1974 Forest Residues Utilization Research and Development Program at Coram Experimental Forest in western Montana. Three levels (high, medium, and low) of biomass removal intensity combined with broadcast burning treatment were assigned after clearcut in western larch (Larix occidentalis Nutt.) stands in 1974. From 1976 to 79, twenty five 2 + 0 bare root seedlings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were consecutively planted in rows. In 2013, tree height, dbh (diameter at breast height), foliar N and C concentrations were measured. From cross-sectional sapwood area, growth efficiency (the ratio of 5-year-basal area increment to total leaf area) was calculated. Previous measurements from 1980, 1987, 1992, and 2001 were used for dbh and height growth analyses. At this site, none of the response variables were affected by biomass removal level. Only seedling planting year contributed significantly to affect tree mean height, dbh, volume. Growth efficiency was not affected by any treatment. These results indicate no apparent effect of biomass removal on site productivity for the range of biomass harvest levels performed.

Elevated ozone affects C, N and P ecological stoichiometry and nutrient resorption of two poplar clones

Article

Nov 2017

The effects of elevated ozone on C (carbon), N (nitrogen) and P (phosphorus) ecological stoichiometry and nutrient resorption in different organs including leaves, stems and roots were investigated in poplar clones 546 (P. deltoides cv. '55/56' × P. deltoides cv. 'Imperial') and 107 (P. euramericana cv. '74/76') with a different sensitivity to ozone. Plants were exposed to two ozone treatments, NF (non-filtered ambient air) and NF60 (NF with targeted ozone addition of 60 ppb), for 96 days in open top chambers (OTCs). Significant ozone effects on most variables of C, N and P ecological stoichiometry were found except for the C concentration and the N/P in different organs. Elevated ozone increased both N and P concentrations of individual organs while for C/N and C/P ratios a reduction was observed. On these variables, ozone had a greater effect for clone 546 than for clone 107. N concentrations of different leaf positions ranked in the order upper > middle > lower, showing that N was transferred from the lower senescent leaves to the upper ones. This was also indicative of N resorption processes, which increased under elevated ozone. N resorption of clone 546 was 4 times larger than that of clone 107 under ambient air (NF). However, elevated ozone (NF60) had no significant effect on P resorption for both poplar clones, suggesting that their growth was only limited by N, while available P in the soil was enough to sustain growth. Understanding ecological stoichiometric responses under ozone stress is crucial to predict future effects on ecological processes and biogeochemical cycles.

Elevated CO 2 and temperature alter development and food utilization of Spodoptera litura fed on resistant soybean

Article

Oct 2017

Effects of elevated atmospheric CO2 (elevated CO2 vs. ambient CO2) and temperature (+0.67–0.79°C vs. ambient temperature) on the developmental life cycle of Spodoptera litura and the food utilization of the fourth-instar larvae fed on soybean (resistant cultivar Lamar vs. susceptible landrace JLNMH) grown in open-top chambers were studied from 2013 to 2015. The results indicated that: (i) compared with ambient CO2, elevated CO2 significantly prolonged the duration of larva and pupa, and adult longevity; significantly decreased the pupation rate, pupal weight, fecundity, the relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD); and increased the relative consumption rate (RCR) and approximate digestibility (AD). (ii) Compared with ambient temperature, elevated temperature significantly shortened the duration of larva and pupa; significantly decreased the pupal weight; and increased the RGR, RCR, ECD and ECI. (iii) Compared with the susceptible soybean accession JLNMH, the resistant soybean cultivar Lamar significantly prolonged the duration of larva and pupa; significantly decreased the pupation rate, pupal weight, adult longevity, fecundity and RGR, RCR and AD; and increased the indexes of ECD. (iv) At elevated temperature, S. litura fed on resistant vs. susceptible cultivars showed opposite trends in the RGR, RCR, AD, ECD and ECI. In addition, elevated temperature under elevated CO2 significantly decreased the RGR (2014), ECD (2013 & 2014) and ECI (2013) and increased the AD (2013 & 2014) compared with other treatment combinations when S. litura fed on Lamar. Future climatic change of temperature and CO2 concentration would likely affect growth and food utilization of S. litura, with increased food intake, but the reduced fecundity may compensate for the increased food consumption, resulting in no significant reduction in insect-induced yield loss in soybean production. Nevertheless, use of insect resistant soybean cultivars will aid in ecological management of S. litura and reduce the insecticide load in soybean production.

Current and future ozone risks to global terrestrial biodiversity and ecosystem processes

Article

Full-text available

Nov 2016

Risks associated with exposure of individual plant species to ozone (O3) are well documented, but implications for terrestrial biodiversity and ecosystem processes have received insufficient attention. This is an important gap because feedbacks to the atmosphere may change as future O3 levels increase or decrease, depending on air quality and climate policies. Global simulation of O3 using the Community Earth System Model (CESM) revealed that in 2000, about 40% of the Global 200 terrestrial ecoregions (ER) were exposed to O3 above thresholds for ecological risks, with highest exposures in North America and Southern Europe, where there is field evidence of adverse effects of O3, and in central Asia. Experimental studies show that O3 can adversely affect the growth and flowering of plants and alter species composition and richness, although some communities can be resilient. Additional effects include changes in water flux regulation, pollination efficiency, and plant pathogen development. Recent research is unraveling a range of effects belowground, including changes in soil invertebrates, plant litter quantity and quality, decomposition, and nutrient cycling and carbon pools. Changes are likely slow and may take decades to become detectable. CESM simulations for 2050 show that O3 exposure under emission scenario RCP8.5 increases in all major biomes and that policies represented in scenario RCP4.5 do not lead to a general reduction in O3 risks; rather, 50% of ERs still show an increase in exposure. Although a conceptual model is lacking to extrapolate documented effects to ERs with limited or no local information, and there is uncertainty about interactions with nitrogen input and climate change, the analysis suggests that in many ERs, O3 risks will persist for biodiversity at different trophic levels, and for a range of ecosystem processes and feedbacks, which deserves more attention when assessing ecological implications of future atmospheric pollution and climate change.

Effects of elevated CO2 concentration on water use efficiency of Tamarix ramosissima in an extremely arid region

Article

Full-text available

Oct 2016
ENVIRON EARTH SCI

The variation of net photosynthetic rate (Pn), transpiration rate (Tr), and intercellular CO2 concentration (Ci) with changes in light intensity of Tamarix ramosissima leaves was studied during the growing seasons of 2012 and 2013 in the extremely arid region of Ejina Oasis, using the LI-6400 portable photosynthesis measurement system. Results indicate that Ci decreased and Pn and Tr increased with light intensity. After reaching the light saturation point, Pn decreased gradually with the enhanced greater light intensity. The apparent maximum photosynthetic rate increased with CO2 concentration, from 17.69 to 27.05 µmol/(m² s); apparent quantum efficiency also increased, as did the light saturation point of T. ramosissima leaves. Water use efficiency (WUE) increased initially but gradually decreased after maximizing with the enhanced light intensity. Tr and Ci increased with elevated CO2 concentration. Pn and WUE increased with CO2 concentration when that concentration was 200–600 µmol/mol. When that concentration increased to 1000 µmol/mol, WUE increased initially but eventually decreased.

ÉCLAIRE Effects of Climate Change on Air Pollution Impacts and Response Strategies for European Ecosystems Seventh Framework Programme Theme: Environment Project Final Report

Technical Report

Full-text available

Dec 2015

Spectroscopic determination of ecologically relevant plant secondary metabolites

Article

Full-text available

May 2016
Methods Ecol. Evol.

Spectroscopy has recently emerged as an effective method to accurately characterize leaf biochemistry in living tissue through the application of chemometric approaches to foliar optical data, but this approach has not been widely used for plant secondary metabolites. Here, we examine the ability of reflectance spectroscopy to quantify specific phenolic compounds in trembling aspen ( Populus tremuloides ) and paper birch ( Betula papyrifera ) that play influential roles in ecosystem functioning related to trophic‐level interactions and nutrient cycling. Spectral measurements on live aspen and birch leaves were collected, after which concentrations of condensed tannins (aspen and birch) and salicinoids (aspen only) were determined using standard analytical approaches in the laboratory. Predictive models were then constructed using jackknifed, partial least squares regression ( PLSR ). Model performance was evaluated using coefficient of determination ( R ² ), root‐mean‐square error ( RMSE ) and the per cent RMSE of the data range (% RMSE ). Condensed tannins of aspen and birch were well predicted from both combined ( R ² = 0·86, RMSE = 2·4, % RMSE = 7%)‐ and individual‐species models (aspen: R ² = 0·86, RMSE = 2·4, % RMSE = 6%; birch: R ² = 0·81, RMSE = 1·9, % RMSE = 10%). Aspen total salicinoids were better predicted than individual salicinoids (total: R ² = 0·76, RMSE = 2·4, % RMSE = 8%; salicortin: R ² = 0·57, RMSE = 1·9, % RMSE = 11%; tremulacin: R ² = 0·72, RMSE = 1·1, % RMSE = 11%), and spectra collected from dry leaves produced better models for both aspen tannins ( R ² = 0·92, RMSE = 1·7, % RMSE = 5%) and salicinoids ( R ² = 0·84, RMSE = 1·4, % RMSE = 5%) compared with spectra from fresh leaves. The decline in prediction performance from total to individual salicinoids and from dry to fresh measurements was marginal, however, given the increase in detailed salicinoid information acquired and the time saved by avoiding drying and grinding leaf samples. Reflectance spectroscopy can successfully characterize specific secondary metabolites in living plant tissue and provide detailed information on individual compounds within a constituent group. The ability to simultaneously measure multiple plant traits is a powerful attribute of reflectance spectroscopy because of its potential for in situ – in vivo field deployment using portable spectrometers. The suite of traits currently estimable, however, needs to expand to include specific secondary metabolites that play influential roles in ecosystem functioning if we are to advance the integration of chemical, landscape and ecosystem ecology.

Effects of elevated CO2 on the physiology and yield parameters of bean

Article

May 2003
Agronomie

The effects of elevated CO2 on bean (Phaseolus vulgaris) physiology were analysed in greenhouses at 350 μl/l and at 700 μl/l (i.e. twice the actual level). The photosynthesis of beans grown under high CO2 concentration increased (+73% until the 40th day after germination). At high concentration, leaf nitrogen content was 15% lower while the C/N ratio was 19% higher. Leaf soluble and unsoluble sugar contents increased (+49 and +64%, respectively). The CO2 doubling significantly increased leaf area by 36% and leaf mass by 57%. Two months after sowing, plants exposed to 700 μl/1 produced pods with higher fresh and dry weights (+44 and +110%, respectively). The individual pod dry weight and length also were also higher (+100 and +10%) but the number of seeds per pod was reduced (-9%). The soluble sugar content increased by 41%. In summary, the results suggest that the CO2 doubling has an important effect on bean yield, particularly on the quantitative level, but the increase in the soluble sugar content was more important on the qualitative level.

Feng GCB-CO2 meta

Data

Nov 2015

Photosynthesis and growth responses of mustard (Brassica juncea L. Cv. Pusa Bold) plants to free air carbon dioxide enrichment (FACE)

Article

Full-text available

Jul 2015
PROTOPLASMA

Increased atmospheric [CO2] is likely to affect photosynthesis, plant growth, and yield potential of plants. Mustard (Brassica juncea L.) is an important oil seed crop that is widely grown in India. Therefore, the impact of elevated [CO2] (585 μmol mol−1) on pigment and protein content, chlorophyll a fluorescence, photosynthetic electron transport reactions, CO2 assimilation, biomass production, and seed yield potential was measured in B. juncea cv Pusa Bold, grown inside free air carbon dioxide enrichment (FACE) rings installed on the campus of Jawaharlal Nehru University, New Delhi, India. Plants were grown for three consecutive winter seasons (2010—2013), in ambient (385 μmol mol−1) or elevated [CO2], in field conditions. Elevated [CO2] had no significant effect on the minimal chlorophyll fluorescence (F 0), while the quantum efficiency of Photosystem II, measured as variable fluorescence (F v = F m–F 0) to maximum fluoresence (F m), increased by 3 %. Electron transport rate, photosystem I, photosystem II, and whole chain electron transport rates increased by 8 % in elevated [CO2]. However, the net photosynthesis rate increased by ≈50 % in three growing seasons under elevated [CO2] condition. The stomatal conductance and transpiration rate decreased resulting in higher photosynthetic water use efficiency. The photosynthesizing surface, i.e., leaf area index substantially increased leading to higher biomass and seed yield under elevated [CO2] condition. Acclimatory downregulation of photosynthesis and plant productivity was not observed in three consecutive growing years suggesting that in the absence of nutrient limitation, B. juncea is highly responsive to elevated CO2 whose yield potential shall increase in changing climatic conditions.

A review of the potential effects of climate change on quaking aspen (Populus tremuloides) in the Western United States and a new tool for surveying sudden aspen decline

Article

Full-text available

Jan 2011

Change of Soil Carbon Fractions and Water-Stable Aggregates in a Forest Ecosystem Succession in South China

Article

Full-text available

Aug 2015

In order to evaluate the dynamics of carbon storage during forest succession and explore the significance of water relations and soil stability in forest environments, a study was conducted in 2011. This study investigated the dynamics of soil organic carbon (SOC) fractions and its protection through aggregation along the successional forests. An experiment in South China examined pine forest (PF), pine and broadleaved mixed forest (PBMF), and monsoon evergreen broadleaf forest (MEBF), which represent the early, middle, and advanced succession stages, respectively. Soil was sampled at 0-15, 15-30, 30-45, and 45-60 cm depths. We analyzed active, slow, and passive organic carbon, as well as particulate organic matter carbon (POM-C) and nitrogen (POM-N), and measured the weight and concentration of water-stable aggregates in four classes (>2000 μm, 250-2000 μm, 53-250 μm, and <53 μm). The results suggested that various carbon fractions and the percentage of active and passive carbon to total organic carbon (TOC) increased with forest succession. The percentage of water-stable aggregates in >2000 μm (0-15 cm and 15-30 cm) and <53 μm (45-60 cm) in MEBF was significantly higher than in PBMF and PF. The SOC content of all size classes of water-stable aggregates in 0-45 cm were significantly increased with forest succession. In conclusion, forest succession contributed to the accumulation of carbon storage, and the increasing percentage of silt- and clay-size (<53 μm) fraction improved the stability of soil organic matter (SOM).

Catharanthus roseus L. and Ocimum sanctum L. as Sensors for Air Pollution

Chapter

Apr 2024

The expansion of urban areas, the acceleration of traffic, the acceleration of economic growth, and the excessive use of energy are all characteristics of industrialized nations that have contributed to the worsening of air pollution. The integrity of the natural world is compromised by all these elements, which have a domino effect on one another and work together to harm it. A major ecological problem is the regional effects of air pollution on various plant species. Unlike animal populations, plant populations are constantly (24/7) and directly exposed to the danger of pollution. Biochemical, physiological, morphological, and anatomical reactions are among the many ways in which these organisms take in, store, and process contaminants that land on their surfaces. This research aims to find out how two possible therapeutic plant species Catharanthus roseus L. and Ocimum sanctum L. react to different levels of air pollution (vehicular pollution) in terms of their morphology, physiology, biochemistry, and pharmacognosy.

Can ethylenediurea (EDU) alter the effects of ozone on the source-sink regulation of nitrogen uptake and remobilization during grain filling period in rice?

Article

Apr 2024
SCI TOTAL ENVIRON

Increased surface ozone (O3) pollution seriously threatens crop production, and ethylenediurea (EDU) can alleviate crop yield reduction caused by O3. However, the reason for the decrease in grain nitrogen (N) accumulation caused by O3 and whether EDU serves as N fertilizer remain unclear. An experiment was conducted to investigate the impacts of factorial combinations of O3 enrichment (ambient air plus 60 ppb) and EDU (foliage spray with 450 ppm solutions) on N concentration, accumulation and remobilization in hybrid rice seedlings. Compared to ambient condition, elevated O3 significantly inhibited the N accumulation in vegetative organs during anthesis and grain N accumulation during the maturity stage. Elevated O3 significantly decreased the total N accumulation duringanthesis and maturity stages, with a greater impact at the latter stage. The decrease in grain N accumulation caused by O3 was attributed to a decrease in N remobilization of vegetative organs during the grain filling period as well as to a decrease in post-anthesis N uptake. However, there was no significant change in the proportion of N remobilization and N uptake in grain N accumulation. The inhibitory effect of O3 on N remobilization in the upper canopy leaves was greater than that in the lower canopy leaves. In addition, elevated O3 increased the N accumulation of panicles at the anthesis stage, mainly by resulting in earlier heading of rice. EDU only increased N accumulation at the maturity stage, which was mainly attributed to an increase in rice biomass by EDU. EDU had no significant effect on N concentration, N remobilization process, and N harvest index. The findings are helpful to better understand the utilization of N fertilizer by rice under O3 pollution, andcan also provide a theoretical basis for sustainable nutrient management to alleviate the negative impact of O3 on crop yield and quality.

Defensive traits of Fagus crenata leaves after long-term CO 2 exposure in free-air CO 2 enrichment (FACE) system

Article

Dec 2023

Response of carbon, nitrogen and phosphorus concentration and stoichiometry of plants and soils during a soybean growth season to O3 stress and straw return in Northeast China

Article

Feb 2022
SCI TOTAL ENVIRON

Carbon (C), nitrogen (N) and phosphorus (P) concentrations and stoichiometry play important roles in biogeochemical cycles of the ecosystems, yet it is still unclear how the allocations of C, N and P concentrations and stoichiometry among plant organs and soils related to O3 stress and straw return. Here, a pot experiment was conducted in open top chambers to monitor the response of C, N and P concentrations and stoichiometry of leaves, stems, roots and soils during a growing season (branching, flowering and podding stages) of soybean (Glycine max; a species highly sensitive to O3) to background O3 concentration (44.8 ± 5.6 ppb), O3 stress (79.7 ± 5.4 ppb) and straw treatment (no straw return and straw return). O3 stress significantly decreased root biomass. Straw return significantly increased root biomass under O3 stress at branching and flowering stages. Generally, O3 stress and straw return showed significant effects on the C, N and P concentrations of leaves and soils, and stoichiometric ratios of leaves, stems and microbial biomass. The C, N and P concentrations and stoichiometry of leaves, stems, roots and soils in response to O3 stress and straw return at the branching stage were inconsistent with the changes observed at the flowering and podding stages. The P conversion efficiency showed significant relationship with root P concentration under the combined effects of O3 stress and straw return. Altogether, the present study indicated that C, N and P concentrations of soybean might be more important than stoichiometric ratios as a driver of root defence against O3 stress in the case of straw return.

Magnitude and mechanisms of nitrogen‐mediated responses of tree biomass production to elevated CO2: A global synthesis

Article

Full-text available

Sep 2021
J ECOL

Elevated atmospheric CO2 concentration (eCO2) typically stimulates tree growth, which is mediated by nitrogen (N) availability; but how N regulates tree biomass responses to eCO2 remains uncertain, which limits our prediction of forest carbon (C) cycling under future global change scenarios. A meta‐analysis of a global dataset including 3,399 observations from 283 papers published from 1980s to February 2021 was conducted with the aim of elucidating N‐mediated responses of tree biomass production to eCO2 and the underlying mechanisms. We found that eCO2 stimulated tree biomass production (+32.0%), while it induced accumulation of non‐structural carbohydrates in leaves rather than in woods and roots, suggesting that the production may be C‐limited but depend on the sink strength of organs. Biomass responses to eCO2 of N‐fertilized trees (+39.6%) were 68.4% greater than those of non‐fertilized trees (+23.5%), confirming that tree growth is also N‐limited. Such N limitation was alleviated by the eCO2‐induced increases in N uptake and N‐use efficiency (NUE), with the former being more important. Increases in tree N pool arose from the enhanced production of fine roots with a lower specific root length, whereas increases in NUE resulted from the flexibility in tissue C:N ratios instead of N resorption efficiency. The positive responses of tree biomass production to eCO2 were greater for ectomycorrhizal trees and conifers than for arbuscular mycorrhizal trees and angiosperms, respectively. Synthesis. Our findings suggest that eCO2 stimulates tree biomass production by increasing C availability, and alleviating N limitation in a feedback way via enhancing N uptake and NUE, and they improve our mechanistic understanding of responses of forest productivity and C sequestration to eCO2 under global change.

Response of C, N and P Ecological Stoichiometry in Plants and Soils During a Soybean Growth Season to O3 Stress and Straw Return in Northeast China

Preprint

Full-text available

Jun 2021

AimsC, N and P ecological stoichiometry plays important roles on biogeochemical cycles in ecosystems, yet the relationship between plant and soil stoichiometry and stoichiometric effects on the growth of soybean root in response to the O 3 stress and straw return remain poorly understood. Methods Here, a pot experiment was conducted in open top chambers to monitor the response of C, N and P ecological stoichiometry of leaves, shoots, roots and soils during a growing season (branching, flowering and podding stages) of soybean (Glycine max; a highly sensitive species to O 3 ) to background O 3 concentration (45 ± 10 ppb), O 3 stress (80 ±10 ppb) and straw treatment (no straw return and straw return). ResultsThe O 3 stress significantly decreased root biomass. The straw return significantly increased root biomass under the O 3 stress at branching and flowering stages. Generally, the O 3 stress and straw return showed significant effects on the C, N, P concentrations of leaves and soils, and stoichiometric ratios of leaves, shoots and microbial biomass. C, N, P concentrations and stoichiometric ratios of leaves, shoots, roots and soils responses to the O 3 stress and straw return at branching stage were inconsistent with changes observed at the flowering and podding stages. The P conversion efficiency showed significant relationship with root P concentration under the combined effects of O 3 stress and straw return. ConclusionsC, N, and P concentrations of soybean might be more important than stoichiometric ratios as a driver of defense against the O 3 stress in the case of straw return.

Causes and Consequences of Condensed Tannin Variation in Populus

Chapter

Apr 2021

Condensed tannins (CTs), synthesized via the phenylpropanoid and malonic acid pathways, occur in Populus tissues at widely varying concentrations. Both concentration and molecular structure are determined by the independent and interactive effects of genetic, ontogenetic, and environmental factors that influence molecular control of CT synthesis, other secondary metabolite production, and plant growth. CTs have a limited role in defending Populus against herbivores, but are associated with pathogen resistance, structuring of herbivore and soil microbial communities, and regulation of soil ecosystem processes (e.g. respiration, decomposition, nutrient cycling) with feedbacks to plant fitness. Shifts in CT expression and distribution resulting from human‐mediated environmental changes are likely to alter organismal interactions, community and ecosystem functions, and evolutionary processes. Future research should aim to strengthen understanding of causal connections between CTs and their biological effects across scales of organization, space and time, and to elucidate how environmental change influences CT production, biochemical tradeoffs, and interrelationships with plant fitness that drive evolutionary processes.

Responses of nitrogen concentrations and pools to multiple environmental change drivers: A meta-analysis across terrestrial ecosystems

Article

Full-text available

Feb 2019
GLOBAL ECOL BIOGEOGR

Aim We sought to understand how the individual and combined effects of multiple environmental change drivers differentially influence terrestrial nitrogen (N) concentrations and N pools and whether the interactive effects of these drivers are mainly antagonistic, synergistic or additive. Location Worldwide. Time period Contemporary. Major taxa studied Plants, soil, and soil microbes in terrestrial ecosystems. Methods We synthesized data from manipulative field studies from 758 published articles to estimate the individual, combined and interactive effects of key environmental change drivers (elevated CO2, warming, N addition, phosphorus addition, increased rainfall and drought) on plant, soil, and soil microbe N concentrations and pools using meta‐analyses. We assessed the influences of moderator variables on these effects through structural equation modelling. Results We found that (a) N concentrations and N pools were significantly affected by the individual and combined effects of multiple drivers, with N addition (either alone or in combination with another driver) showing the strongest positive effects; (b) the individual and combined effects of these drivers differed significantly between N concentrations and N pools in plants, but seldom in soils and microbes; (c) additive effects of driver pairs on N concentrations and pools were much more common than synergistic or antagonistic effects across plants, soils and microbes; and (d) environmental and experimental factors were important moderators of the individual, combined and interactive effects of these drivers on terrestrial N. Main conclusions Our results indicate that terrestrial N concentrations and N pools, especially those of plants, can be significantly affected by the individual and combined effects of environmental change drivers, with the interactive effects of these drivers being mostly additive. Our findings are important because they contribute to the development of models to better predict how altered N availability affects ecosystem carbon cycling under future environmental changes.

Ecosystem scale trade-off in nitrogen acquisition pathways

Article

Full-text available

Nov 2018
Nat. Ecol. Evol.

The nitrogen (N) cycle in terrestrial ecosystems is strongly influenced by resorption before litter fall and by mineralization after litter fall. Although both resorption and mineralization make N available to plants and are influenced by climate, their linkage in a changing environment remains largely unknown. Here, our synthesis study shows that, at the global scale, increasing N-resorption efficiency negatively affects the N-mineralization rate. As temperature and precipitation increase, the increasing rates of N cycling closely correspond to a shift from the more conservative resorption pathway to the mineralization pathway. Furthermore, ecosystems with faster N-cycle rates support plant species that have higher foliar N:P ratios and microbial communities with lower fungi:bacteria ratios. Our study shows an ecosystem scale trade-off in N-acquisition pathways. We propose that incorporating the dynamic interaction between N resorption and N mineralization into Earth system models will improve the simulation of nutrient constraints on ecosystem productivity.

Changes in nutrients and decay rate of Ginkgo biloba leaf litter exposed to elevated O 3 concentration in urban area

Article

Full-text available

Mar 2018

Ground-level ozone (O 3 ) pollution has been widely concerned in the world, particularly in the cities of Asia, including China. Elevated O 3 concentrations have potentially influenced growth and nutrient cycling of trees in urban forest. The decomposition characteristics of urban tree litters under O 3 exposure are still poorly known. Ginkgo biloba is commonly planted in the cities of northern China and is one of the main tree species in the urban forest of Shenyang, where concentrations of ground-level O 3 are very high in summer. Here, we hypothesized that O 3 exposure at high concentrations would alter the decomposition rate of urban tree litter. In open-top chambers (OTCs), 5-year-old G. biloba saplings were planted to investigate the impact of elevated O 3 concentration (120 ppb) on changes in nutrient contents and decomposition rate of leaf litters. The results showed that elevated O 3 concentration significantly increased K content (6.31 ± 0.29 vs 17.93 ± 0.40, P < 0.01) in leaves of G. biloba , significantly decreased the contents of total phenols (2.82 ± 0.93 vs 1.60 ± 0.44, P < 0.05) and soluble sugars (86.51 ± 19.57 vs 53.76 ± 2.40, P < 0.05), but did not significantly alter the contents of C, N, P, lignin and condensed tannins, compared with that in ambient air. Furthermore, percent mass remaining in litterbags after 150 days under ambient air and elevated O 3 concentration was 56.0% and 52.8%, respectively. No significant difference between treatments was observed in mass remaining at any sampling date during decomposition. The losses of the nutrients in leaf litters of G. biloba showed significant seasonal differences regardless of O 3 treatment. However, we found that elevated O 3 concentration slowed down the leaf litter decomposition only at the early decomposition stage, but slightly accelerated the litter decomposition at the late stage (after 120 days). This study provides our understanding of the ecological processes regulating biogeochemical cycles from deciduous tree species in high-O 3 urban area.

Effects of Climate Change and Ozone Concentration on the Net Primary Productivity of Forests in South Korea

Article

Full-text available

Mar 2018

Tropospheric ozone impacts the health and productivity of forest ecosystems. The concentration of ozone on Earth will increase in the future, particularly in China and its neighboring countries, including Korea, due to a projected rise in nitrogen dioxide and ozone precursors as a result of China's emissions. This study aims to estimate the effect of changes in ozone concentration and climate change on the forests in Korea, based on expected nitrogen dioxide emissions in Korea and China in the future. To do this, we developed an empirical model that represents the statistical relationship between the net primary productivity (NPP) of the forests and ozone concentration using historical data; and, estimated the future NPP of the forests under future ozone concentration scenarios based on nitrogen dioxide emissions of the Shared Socioeconomic Pathway (SSP) scenarios. The analysis suggests that the ozone concentration begin exerting effects to the NPP, about 68.10 tC/km²/year decrement per 0.01 ppm increment. We estimated that the NPP of Korean forests has been reduced by 8.25% due to the current concentration of ozone, and the damage is estimated to increase to a range between 8.47% and 10.55% in the 2050s, and between 5.85% and 11.15% in the 2090s depending on the scenarios.

Phosphorus Enhances Uptake of Dissolved Organic Matter in Boreal Streams

Article

Full-text available

Jun 2018
ECOSYSTEMS

Retention of carbon (C), either by physical mechanisms or microbial uptake, is a key driver of the transformation and storage of C and nutrients within ecosystems. Both the molecular composition and nutrient content of organic matter influence the rate at which it is retained in streams, but the relative influence of these characteristics remains unclear. We estimated the effects of nutrient content and molecular composition of dissolved organic C (DOC) on uptake in boreal streams by measuring rates of C retention, in situ, following introduction of leachates derived from alder, poplar, and spruce trees subject to long-term fertilization with nitrogen (N) or phosphorus (P). Leachate C:N varied approximately twofold, and C:P varied nearly 20-fold across species and nutrient treatments. Uptake of DOC was greatest for leachates derived from trees that had been fertilized with P, a finding consistent with P-limitation of uptake and/or preferential sorption of P-containing molecules. Optical measures indicated that leachates derived from the three tree species varied in molecular composition, but uptake of DOC did not differ across species, suggesting weak constraints on retention imposed by molecular composition relative to nutrient limitation. Observed coupling between P and C cycles highlights the potential for increased P availability to enhance DOC retention in headwater streams.

Genetic Modification of Lignin in Hybrid Poplar (Populus alba × Populus tremula) Does Not Substantially Alter Plant Defense or Arthropod Communities

Article

Full-text available

Jun 2017
J INSECT SCI

Lignin impedes access to cellulose during biofuel production and pulping but trees can be genetically modified to improve processing efficiency. Modification of lignin may have nontarget effects on mechanical and chemical resistance and subsequent arthropod community responses with respect to pest susceptibility and arthropod biodiversity. We quantified foliar mechanical and chemical resistance traits in lignin-modified and wild-type (WT) poplar (Populus alba × Populus tremula) grown in a plantation and censused arthropods present on these trees to determine total abundance, as well as species richness, diversity and community composition. Our results indicate that mechanical resistance was not affected by lignin modification and only one genetic construct resulted in a (modest) change in chemical resistance. Arthropod abundance and community composition were consistent across modified and WT trees, but transgenics produced using one construct exhibited higher species richness and diversity relative to the WT. Our findings indicate that modification of lignin in poplar does not negatively affect herbivore resistance traits or arthropod community response, and may even result in a source of increased genetic diversity in trees and arthropod communities.

Ozone Effects on Forest Ecosystems under a Changing Global Environment

Article

Jan 2005

D.F. Karnosky

Tropospheric ozone [O3] continues to be an important problem for forest ecosystems in many regions of the world. At the same time, atmospheric carbon dioxide [CO2] is rising at unprecedented rates over the entire globe. Little is known as to how forest ecosystems will respond to [O3] under elevated [CO2]. In this paper, I summarize a long-term (7-year) study of the impacts of elevated [CO2] and [O3], alone and in combination, on a northern hardwood forest ecosystem consisting of two pioneer species (Populus tremuloides Michx. and Betula papyrifera Marsh.) and a later successional species (Acer saccharum Marsh.) grown under an open-air exposure (FACE) system.

Soil nitrogen transformations under Populus tremuloides, Betula papyrifera and Acer saccharum following 3 years exposure to elevated CO2 and O-3

Article

Dec 2003

Increases in atmospheric CO2 and tropospheric O-3 may affect forest N cycling by altering plant litter production and the availability of substrates for microbial metabolism. Three years following the establishment of our free-air CO2-O-3 enrichment experiment, plant growth has been stimulated by elevated CO2 resulting in greater substrate input to soil; elevated O-3 has counteracted this effect. We hypothesized that rates of soil N cycling would be enhanced by greater plant productivity under elevated CO2, and that CO2 effects would be dampened by O-3. We found that elevated CO2 did not alter gross N transformation rates. Elevated O-3 significantly reduced gross N mineralization and microbial biomass N, and effects were consistent among species. We also observed significant interactions between CO2 and O-3: (i) gross N mineralization was greater under elevated CO2 (1.0 mg N kg(-1) day(-1)) than in the presence of both CO2 and O-3 (0.5 mg N kg(-1) day(-1)) and (ii) gross NH4+ immobilization was also greater under elevated CO2 (0.8 mg N kg(-1) day(-1)) than under CO2 plus O-3 (0.4 mg N kg(-1) day(-1)). We used a laboratory N-15 tracer method to quantify transfer of inorganic N to organic pools. Elevated CO2 led to greater recovery of NH4+-N-15 in microbial biomass and corresponding lower recovery in the extractable NO3- pool. Elevated CO2 resulted in a substantial increase in NO3--N-15 recovery in soil organic matter. We observed no O-3 main effect and no CO2 by O-3 interaction effect on N-15 recovery in any soil pool. All of the above responses were most pronounced beneath Betula papyrifera and Populus tremuloides, which have grown more rapidly than Acer saccharum. Although elevated CO2 has increased plant productivity, the resulting increase in plant litter production has yet to overcome the influence of the pre-existing pool of soil organic matter on soil microbial activity and rates of N cycling. Ozone reduces plant litter inputs and also appears to affect the composition of plant litter in a way that reduces microbial biomass and activity.

AIR POLLUTION AND VEGETATION ICP VEGETATION, ANNUAL REPORT 2014/2015

Book

Full-text available

Sep 2015

Methods in forest canopy research

Article

Nov 2012

Poised between soil and sky, forest canopies represent a critical point of exchange between the atmosphere and the earth, yet until recently, they remained a largely unexplored frontier. For a long time, problems with access and the lack of tools and methods suitable for monitoring these complex bioscapes made canopy analysis extremely difficult. Fortunately, canopy research has advanced dramatically in recent decades. Methods in Forest Canopy Research is a comprehensive overview of these developments for explorers of this astonishing environment. The authors describe methods for reaching the canopy and the best ways to measure how the canopy, atmosphere, and forest floor interact. They address how to replicate experiments in challenging environments and lay the groundwork for creating standardized measurements in the canopy-essential tools for for understanding our changing world.

The Regulation by Phenolic Compounds of Soil Organic Matter Dynamics under a Changing Environment

Article

Full-text available

Oct 2015
BMRI

Phenolics are the most abundant plant metabolites and are believed to decompose slowly in soils compared to other soil organic matter (SOM). Thus, they have often been considered as a slow carbon (C) pool in soil dynamics models. Here, however, we review changes in our concept about the turnover rate of phenolics and quantification of different types of phenolics in soils. Also, we synthesize current research on the degradation of phenolics and their regulatory effects on decomposition. Environmental changes, such as elevated CO 2 , warming, nitrogen (N) deposition, and drought, could influence the production and form of phenolics, leading to a change in SOM dynamics, and thus we also review the fate of phenolics under environmental disturbances. Finally, we propose the use of phenolics as a tool to control rates of SOM decomposition to stabilize organic carbon in ecosystems. Further studies to clarify the role of phenolics in SOM dynamics should include improving quantification methods, elucidating the relationship between phenolics and soil microorganisms, and determining the interactive effects of combinations of environmental changes on the phenolics production and degradation and subsequent impact on SOM processing.

Nutrients in Senesced Leaves: Keys to the Search for Potential Resorption and Resorption Proficiency

Article

Full-text available

Sep 1996

Keith Thomas Killingbeck

Analyses of nitrogen and phosphorus in the senesced leaves of 89 species of deciduous and evergreen woody perennials were used (1) to discover the limits of ultimate potential resorption (maximal withdrawal of nutrients from senescing leaves), (2) to determine a means by which resorption can be categorized as complete or incomplete, (3) to develop the concept of resorption proficiency (measured as the levels to which nutrients have been reduced in senesced leaves), (4) to compare resorption in evergreen vs. deciduous species, (5) to assess the impact of phylogeny on resorption, (6) to compare resorption in actinorhizal vs. non-nitrogen-fixing species, and (7) to consider the efficacy of using multiple measures of resorption to answer questions regarding the function and evolution of this process, rather than relying solely on analyses of resorption efficiency (percentage reduction of nutrients between green and senesced leaves). Concentrations of 0.3% nitrogen and 0.01% phosphorus in senesced leaves represent ultimate potential resorption of these nutrients in woody perennials. Resorption proficiency and potential resorption were quantitatively defined in two models that describe both resorption that is maximal and biochemically complete, and that which is not. Resorption is highly proficient in plants that have reduced nitrogen and phosphorus in their senescing leaves to concentrations below 0.7% and 0.05%, respectively. An important feature of knowing the levels to which nutrients can be reduced in senescing leaves is that these values offer an objective gauge by which to measure the success of resorption as a nutrient conservation mechanism. Evergreens were significantly more proficient at resorbing phosphorus than were deciduous species (0.045% vs. 0.067% P in senesced leaves, respectively) and plants capable of symbiotic nitrogen fixation were significantly less proficient at resorbing nitrogen than were nonfixers (1.6% vs. 0.9% N in senesced leaves, respectively). Resorption proficiency appeared to parallel some phylogenic trends, yet the influence of phylogeny was not so significant as to overwhelm the effects of recent selection. The ability of plants to reduce nitrogen in senescing leaves was significantly correlated with their ability to reduce phosphorus. Measurement and analysis of resorption proficiency, when coupled with concurrent consideration of potential resorption and resorption efficiency, should facilitate and expedite the ongoing attempt to resolve complex questions regarding the environmental constraints that influence resorption, and the selection pressures that have directed the evolution of this process.

Regulation of Woody Plant Secondary Metabolism by Resource Availability: Hypothesis Testing by Means of Meta-Analysis

Article

Full-text available

Nov 1998
OIKOS

Our aim in this study was to determine how well phenotypic variation iri foliar concentrations of carbon-based secondary compounds (CBSCs) in woody plants can be predicted on the basis of two resource-based hypotheses, i.e. the carbon-nutrient balance (CNB) and growth-differentiation balance (GDB) hypotheses. We conducted a meta-analysis of literature data with respect to responses of CBSCs, carbohydrates and nitrogen to six types of environmental manipulations (fertilization with nitrogen or phosphorus, shading, CO2 enrichment, drought stress, ozone exposure): Plant responses to nitrogen fertilization, shading and CO2 enrichment in terms of pooled CBSCs and carbohydrates were consistent with predictions made with the two hypotheses. However, among biosynthetically distinct groups of CBSCs only concentrations of phenylpropanoid-derived compounds changed as predicted; hydrolyzable tannins and terpenoids, in particular, were less responsive. Phosphorus fertilization did not affect concentrations of CBSC or primary metabolites. Plant responses to drought and ozone exposure presumably were driven by plant demands for particular types of compounds (osmolites in the case of drought and antioxidants in the case of ozone exposure) rather than by changes in resource availability. Based on the relative importance of the treatment effects, we propose a hierarchical model of carbon allocation to CBSCs. The model implies that CBSC production is determined by both resource availability and specific demand-side responses. However, these two mechanisms work at different hierarchical levels. The domain of the CNB and GDB hypotheses is at the high hierarchical levels, predicting the total amount of carbon that can be allocated to CBSCs. Predicting altered concentrations of individual CBSCs, i.e. low hierarchy levels, probably demands biosynthetically detailed models which also take into account the history of plant interactions with biotic and abiotic factors.

Carbon-based Secondary Compounds at Elevated CO 2

Article

Full-text available

Mar 1997

From literature sources we compiled the data on carbon-based-secondary compounds CBSC (phenolics and terpenoids) and biomass of 17 plant species grown at different CO2 concentrations under low and high nutrient availabilities. With a low nutrient availability a possible inverse correlation was found between the biomass and CBSC changes. On the contrary, under a high nutrient availability, both the CBSC and biomass increased with elevated CO2. The wide variation in the CBSC production among species and compounds (larger responses in phenolics than in terpenoids) indicates that the allocation to CBSC may not completely be governed by changes in CO2 and nutrient availabilities per se. Yet the comparison shows that elevated CO2 generally loads the carbon into CBSC [their leaf concentration increased an overall average of 14 % at 700 umol(CO2) mol-r] which may improve our understanding of the carbon storage and cycling in ecosystems under the “global change” of climate.

Effects of COâ and NOââ» availability on deciduous trees: Phytochemistry and insect performance

Article

Full-text available

Jan 1997

Increasing concentrations of atmospheric COâ will interact with other environmental factors to influence the physiology and ecology of trees. This research evaluated how plant phytochemical responses to enriched atmospheric COâ are affected by the availability of soil nitrate (NOââ») and how these chemical changes alter performance of a tree-feeding folivore. Seedlings of three deciduous tree species were grown in ambient or elevated COâ in combination with low or high soil NOââ» availability. Lymantria dispar larvae were reared on foliage (aspen and maple). Concentrations of nitrogen and soluble protein decreased, whereas concentrations of starch, condensed tannins, and ellagitannins increased, in response to elevated COâ and/or low NOââ». Responses of simple carbohydrates and phenolic glycosides were variable absolute (net) changes in foliar C:N ratios were greatest for aspen and least for oak, whereas relative changes were greatest for maple and least for aspen. Elevated COâ treatments had little effect on gypsy moth development time, growth rate, or larval mass. Larvae reared on aspen foliage grown under elevated COâ exhibited increased consumption but decreased conversion efficiencies. Gypsy moth responses to NOââ» were strongly host specific. The magnitude of insect response elicited by resource-mediated shifts in host chemistry will depend on how levels of compounds with specific importance to insect fitness are affected. Relatively few true interactions occured between carbon and nitrogen availability and insect performance. Tree species frequently interacted with COâ and/or NOââ» availability to affect both parameters. The effects of elevated atmospheric COâ on terrestrial plant communities will depend on species composition and soil nutrient availability. 54 refs., 9 figs., 4 tabs.

Selective Foraging and Ecosystem Processes in Boreal Forests

Article

Full-text available

Apr 1992

We suggest that selective foraging alters feedbacks between plants and decomposers and between plants and herbivores. Plant tissue chemistry is an important link between herbivores and decomposers. Plants that produce easily decomposable litter are also heavily browsed, because the same chemical properties that determine litter decay also determine digestibility. This trait links theories of food webs and nutrient cycles by posing a role of herbivores as functional switches determining both plant community composition and the array of litters returned to the soil. This role appears to be particularly strong in boreal forests, where nutrient availability is low and limits productivity and determines successional pathways, where effects of herbivores are strong and long lasting, and where the same plant traits that determine herbivore preference and response to browsing also determine interactions with soil nutrient availability. Such feedbacks cause the effects of herbivores on ecosystems to persist even after the herbivores are no longer present.

Nitrogen resorption in senescing tree leaves in a warmer, CO2-enriched atmosephere

Article

Full-text available

Sep 2000

The prediction that litter quality, and hence litter decomposition rates, would be reduced when plants are grown in a CO2-enriched atmosphere has been based on the observation that foliar N concentrations usually are lower in elevated [CO2]. The implicit assumption is that the N concentration in leaf litter reflects the N concentration in green leaves. Here we evaluate that assumption by exploring whether the process of seasonal nutrient resorption is different in CO2-enriched plants. Nitrogen resorption was studied in two species of maple trees (Acer rubrum L. and A. saccharum Marsh.), which were planted in unfertilized soil and grown in open-top chambers with ambient or elevated [CO2] in combination with ambient or elevated temperature. In the second growing season, prior to autumn senescence, individual leaves were collected and analyzed for N and dry matter content. Other leaves at the same and an adjacent node were collected for analysis as they senesced and abscised. This data set was augmented with litter samples from the first growing season and with green leaves and leaf litter collected from white oak (Quercus alba L.) saplings grown in ambient and elevated [CO2] in open-top chambers. In chambers maintained at ambient temperature, CO2 enrichment reduced green leaf N concentrations by 25% in A. rubrum and 19% in A. saccharum. CO2 enrichment did not significantly reduce resorption efficiency so the N concentration also was reduced in litter. There were, however, few effects of [CO2] on N dynamics in these leaves; differences in N concentration usually were the result of increased dry matter content of leaves. The effects of elevated [CO2] on litter N are inherently more difficult to detect than differences in green leaves because factors that affect senescence and resorption increase variability. This is especially so when other environmental factors cause a disruption in the normal progress of resorption, such as in the first year when warming delayed senescence until leaves were killed by an early frost. The results of this experiment support the approach used in ecosystem models in which resorption efficiency is constant in ambient and elevated [CO2], but the results also indicate that other factors can alter resorption efficiency.

Forest atmosphere carbon transfer and storage (FACTS-II) the aspen Free-air CO2 and O3 Enrichment (FACE) project: an overview.

Article

Full-text available

Jan 2000

Substrate control of litter decomposition in Rocky Mountain forests

Article

Full-text available

Oct 1991
CAN J BOT

The influence of chemical and physical quality of litter on its rate of decomposition was examined by measuring mass loss from 19 diverse litter types, including leaves, needles, forbs, wood, and roots in the Kananaskis Valley of Alberta, Canada. Litter samples drawn from three adjacent forests of lodgepole pine, white spruce, and Engelmann spruce – subalpine fir, and from a small clearcut area, were allowed to decompose for 3 years at their sites of origin. The best predictors of mass loss were the initial concentrations of lignin and labile material in the litter. Adding N or P contents as a second term, rather than as a lignin to nutrient ratio, significantly improved mass loss predictions. There were abrupt limits for the influence of lignin (above 28%) and N (below C:N of 30:1); similar limits were observed for all predictors except labile content. None of these chemical parameters, nor a physical measure, particle diameter, were useful in predicting rates of decomposition of high-lignin, woody substrates. The relative importance of the various litter quality parameters in determining rates of mass loss in the clear-cut area was very similar to that in the forests, despite considerably more rapid decomposition in the clearcut. Key words: decomposition, lignin, litter, nutrients, Rocky Mountains, wood.

Nitrogen and Lignin Content as Predictors of Litter Decay Rates: A Microcosm Test

Article

Full-text available

Feb 1989

Leaf litter from 8 species of tree, shrub or herb, ranging in lignin content from 3.4-20.5%, was allowed to decompose in microcosms for up to 4 mo (equivalent to 1.5-2 yr decay in the field). Nitrogen content and the C:N ratio were the best predictors of mass loss rate, and were substantially better than the ligin:N ratio. However, when regressions were tested using pine needles (lignin content 26.2%), the C:N ratio and N content badly underestimated mass remaining, while lignin content and the lignin:N ratio overestimated it by <2%. Regressions of initial lignin content or lignin:N ratio on mass remaining improved from 2 to 4 mo decomposition, while those of N content grew worse, illustrating succession of N to lignin control of decomposition rate. -from Authors

Elevated atmospheric CO2: effects on phytochemistry, insect performance and insect-parasitoid interactions

Article

Full-text available

Jun 1995
GLOBAL CHANGE BIOL

This study was conducted to examine the effects of CO2-mediated changes in tree chemistry on the performance of the gypsy moth ((Lymantria dispar L.) and the parasitold Cotesia melanoscela (Ratz.). We used carbon-nutrient balance theory to develop hypotheses regarding changes in tree chemistry and the performance of both insects under elevated CO2. As predicted, levels of foliar nitrogen declined and concentrations of carbon-based compounds (e.g. starch and phenolics) increased under elevated CO2. Gypsy moth performance (e.g. growth, development) was altered by CO2-mediated changes in foliar chemistry, but the magnitude was small and varied across tree species. Larvae feeding on high CO2 aspen exhibited the largest reduction in performance, relative to larvae feeding on birch, oak, or maple. Parasitism by C. melanoscela significantly prolonged gypsy moth development and reduced growth rates. Overall, the effect of parasitism on gypsy moth performance did not differ between CO2 treatments. Altered gypsy moth performance on high CO2 foliage in turn affected parasitoid performance, but the response was variable: parasitoid mortality increased and adult female size declined slightly under high CO2, while development time and adult male size were unaffected. Our results suggest that CO2-induced changes in plant chemistry were buffered to the extent that effects on third trophic level interactions were weak to non-existent for the system examined in this study.

Genotypic variation in response of quaking aspen (Populus tremuloides) to atmospheric CO2 enrichment

Article

Full-text available

Feb 2001

Enriched atmospheric CO2 alters the quantity and quality of plant production, but how such effects vary among plant genotypes is poorly known. We evaluated the independent and interactive effects of CO2 and nutrient availability on growth, allocation and phytochemistry of six aspen (Populus tremuloides Michx.) genotypes. One-year-old trees, propagated from root cuttings, were grown in CO2-controlled glasshouses for 64 days, then harvested. Foliage was analyzed for levels of water, nitrogen, starch, phenolic glycosides and condensed tannins. Of seven plant growth/allocation variables measured, four (biomass production, stem growth, relative growth rate and root:shoot ratio) exhibited marginally to highly significant CO2 2 genotype interactions. CO2 enrichment stimulated growth of some genotypes more than others, and this interaction was itself influenced by soil nutrient availability. In addition, enriched CO2 increased the magnitude of the among-genotype variance for four of the growth/allocation variables. Of six foliar chemical constituents analyzed, CO2-mediated responses of two (the phenolic glycoside tremulacin and condensed tannins) varied among genotypes. Moreover, enriched CO2 increased the magnitude of among-genotype variance for four of the chemical variables. Given the importance of these growth and chemical characteristics to the biological fitness of aspen, this research suggests that projected atmospheric CO2 increases are likely to alter the genetic structures and evolutionary trajectories of aspen populations.

Decline in gypsy moth (Lymantria dispar) performance in an elevated CO2 atmosphere depends upon host plant species

Article

Full-text available

Oct 1996

Plant species differ broadly in their responses to an elevated CO2 atmosphere, particularly in the extent of nitrogen dilution of leaf tissue. Insect herbivores are often limited by the availability of nutrients, such as nitrogen, in their host plant tissue and may therefore respond differentially on different plant species grown in CO2-enriched environments. We reared gyspy moth larvae (Lymantria dispar) in situ on seedlings of yellow birch (Betula allegheniensis) and gray birch (B. populifolia) grown in an ambient (350 ppm) or elevated (700 ppm) CO2 atmosphere to test whether larval responses in the elevated CO2 atmosphere were species-dependent. We report that female gypsy moths (Lymantria dispar) reared on gray birch (Betula populifolia) achieved similar pupal masses on plants grown at an ambient or an elevated CO2 concentration. However, on yellow birch (B. allegheniensis), female pupal mass was 38% smaller on plants in the elevated-CO2 atmosphere. Larval mortality was significantly higher on yellow birch than gray birch, but did not differ between the CO2 treatments. Relative growth rate declined more in the elevated CO2 atmosphere for larvae on yellow birch than for those on gray birch. In preference tests, larvae preferred ambient over elevated CO2-grown leaves of yellow birch, but showed no preference between gray birch leaves from the two CO2 atmospheres. This differential response of gypsy moths to their host species corresponded to a greater decline in leaf nutritional quality in the elevated CO2 atmosphere in yellow birch than in gray birch. Leaf nitrogen content of yellow birch dropped from 2.68% to 1.99% while that of gray birch leaves only declined from 3.23% to 2.63%. Meanwhile, leaf condensed tannin concentration increased from 8.92% to 11.45% in yellow birch leaves while gray birch leaves only increased from 10.72% to 12.34%. Thus the declines in larval performance in a future atmosphere may be substantial and host-species-specific.

Forest Litter Production, Chemistry, and Decomposition Following Two Years of Free-Air CO 2 Enrichment

Article

Full-text available

Feb 2001

Increases in tree biomass may be an important sink for CO2 as the atmospheric concentration continues to increase. Tree growth in temperate forests is often limited by the availability of soil nutrients. To assess whether soil nutrient limitation will constrain forest productivity under high atmospheric CO2, we studied the changes in forest litter production and nutrient cycling in a maturing southern U.S. loblolly pine-hardwood forest during two years of free-air CO2 enrichment. The objective of this paper is to present data on the chemistry of green leaves and leaf litter, nutrient-retranslocation efficiency, above-ground litter production, whole-system nutrient-use efficiency, decomposition, and N availability in response to forest growth under elevated CO2. The chemical composition of green leaves and leaf litter was largely unaffected by elevated CO2. Green-leaf nitrogen (N) and phosphorus (P) concentrations were not significantly lower under elevated CO2. N and P retranslocation from green leaves did not increase under elevated CO2; therefore, leaf litter N and P concentrations were not significantly lower under elevated CO2. The concentrations of carbon, lignin, and total nonstructural carbohydrates in litter were not significantly different under elevated CO2. Total aboveground litterfall increased significantly with CO2 fumigation. The increase in litterfall was due to significant increases in loblolly pine leaf litter and bark production. The mass of leaves from deciduous species did not increase with CO2 fumigation. Whole-system nutrient-use efficiency (aboveground litterfall/nutrient content of litterfall) did not increase as a consequence of forest growth under elevated CO2, but N and P fluxes from vegetation to the forest floor increased significantly. During the second year of CO2 fumigation, the flux of N and P to the forest floor in litterfall increased by 20% and 34%, respectively. The rate of mass loss during one year of decomposition was unaffected by "litter type" (whether the litter was produced under ambient or elevated CO2), nor by the "site" of decomposition (whether the litter was decomposed in the ambient or elevated CO2 plots). N was immobilized in litter during decomposition, whereas P was mineralized. There was no consistent effect of litter type or site on nutrient dynamics in decomposing litter. There was no significant effect of elevated CO2 on the pool size of inorganic N (NH4 + and NO3 -) in the top 7.5 cm of mineral soil. The rate of net N mineralization and nitrification in mineral soil was not significantly different between treatment and control plots. Identifying the source of the nutrients lost in litterfall is critical to the long-term potential growth stimulation of forests under elevated CO2. If the nutrients lost from biomass come from storage (e.g., the movement of nutrients from wood to leaves), then the increase in litter production should decrease over time as slowly replenished nutrient reserves are exhausted. If the nutrients lost in plant litter are replaced by uptake from soils, then it is possible (1) that trees acquire soil nutrients at a rate commensurate with growth stimulated by elevated CO2; and (2) that forest productivity will be stimulated by elevated CO2 in the long term.

Responses of Diciduous Trees to Elevated Atmospheric CO2: Productivity, Phytochemistry, and Insect Performance

Article

Full-text available

Apr 1993

Rising levels of atmospheric carbon dioxide are expected to directly affect forest ecosystems. This research evaluated the effects of enriched CO[sub 2], on the productivity and phytochemistry of forest trees and performance of associated insects. Our experimental system consisted of three tree species (quaking aspen [Populus tremuloides], red oak [Quercus rubra], sugar maple [Acer saccharum]) and two species of leaf-feeding insects (gypsy moth [Lymantria dispar] and forest tent caterpillar [Malacosma disstria]). Three questions were evaluated: in response to enriched CO[sub 2]: (1) relative increases in tree growth rates (2) relative decreases in protein and increases in carbon-based compounds, and (3) relative reductions in insect performance. Aspen responded the most to enriched CO[sub 2], atmospheres whereas maple responded the least. Proportional growth increases, were highest for oak and least for maple. Effects of elevated CO[sub 2], on biomass allocation patterns differed among the three species. Enriched CO[sub 2], altered concentrations of primary and secondary metabolites in leaves, but the magnitude and direction of effects were species-specific. Consumption rates of insects fed high-CO[sub 2], aspen increased dramatically, but growth rates declined. Gypsy moths grew better on high-CO[sub 2], oak, whereas forest tent caterpillars were unaffected; tent caterpillars grew less on high-CO[sub 2], maple, while gypsy moths were unaffected. Changes in insect performance parameters were related to changes in foliar chemistry. This study illustrates that tree productivity and chemistry, and the performance of associated insects, will change under CO[sub 2], atmospheres predicted for the next century. Changes in higher level ecological processes, such as community structure and nutrient cycling, are also implicated. 61 refs., 3 figs., 2 tabs.

CO2 and light effects on deciduous trees: Growth, foliar chemistry, and insect performance

Article

Full-text available

May 1999

This study examined the effects of CO2 and light availability on sapling growth and foliar chemistry, and consequences for insect performance. Quaking aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), and sugar maple (Acer saccharum Marsh.) were grown in controlled environment greenhouses under ambient or elevated CO2 (38.7 and 69.6 Pa), and low or high light availability (375 and 855 μmol m−2 s−1). Because CO2 and light are both required for carbon assimilation, the levels of these two resources are expected to have strong interactive effects on tree growth and secondary metabolism. Results from this study support that prediction, indicating that the relative effect of rising atmospheric CO2 concentrations on the growth and secondary metabolism of deciduous trees may be dependent on light environment. Trees in ambient CO2-low light environments had substantial levels of phytochemicals despite low growth rates; the concept of basal secondary metabolism is proposed to explain allocation to secondary metabolites under growth-limiting conditions. Differences between CO2 and light effects on the responses of growth and secondary metabolite levels suggest that relative allocation is not dependent solely on the amount of carbon assimilated. The relative growth rates and indices of feeding efficiency for gypsy moth (Lymantria dispar L.) larvae fed foliage from the experimental treatments showed no significant interactive effects of light and CO2, although some main effects and many host species interactions were significant. Gypsy moth performance was negatively correlated with CO2- and light-induced increases in the phenolic glycoside content of aspen foliage. Insects were not strongly affected, however, by treatment differences in the nutritional and secondary chemical components of birch and maple.

The response of plants to rising levels of atmospheric carbon dioxide

Article

Jan 1983

Effects of ozone on crop, forest, and natural ecosystems: Assessment of research needs

Article

Oct 1998

Ozone is the most insidious and ubiquitous air pollutant affecting ecological systems in the United States. In the recent review of the ozone standards (1996-1997), the U.S. Environmental Protection Agency's (EPA) Office of Air Quality Planning and Standards recommended a seasonal, cumulative secondary standard to protect vegetation, if the revised primary standard was not deemed sufficiently strict to protect sensitive ecosystems. However, data gaps and uncertainties made it difficult to justify a secondary standard that was more restrictive than the primary standard, and political and economic concerns proved decisive in setting the revised secondary standard to be the same as the primary. This revision will increase protection to ecological systems but ignores well-accepted facts that plants respond to long-term cumulative ozone exposures and are more sensitive than humans to ozone stress. It is important that the general public recognize that ozone is a critical Stressor of ecological systems. The risk assessment paradigm used by EPA requires that an identification and prioritization of ecological effects research (for the secondary standard) be prepared after each reevaluation of the standards for all "criteria pollutants." In 1997 this was accomplished for ozone through an EPA-sponsored workshop attended by a mix of ecologists, air quality specialists, and other scientists. The workshop highlighted research needed to aid EPA in developing its ecological research agenda before the next review of the secondary standard for ozone. However, it was also recognized that other agencies needed to identify and more fully support aspects of ecological research pertinent to their missions. The workshop participants addressed the needs and responsibilities of EPA and other agencies. The results of the work-shop are highlighted in this paper.

A simple and sensitive method for determining reducing sugars in plant tissues. Application to quantify the sugar content in quinoa (Chenopodium quinoa willd.) Seedlings

Article

Jan 1998

A simple and sensitive method for the colorimetric determination of reducing sugars in plant materials is proposed. The procedure is based on reduction under alkaline conditions of potassium ferricyanide by the reducing groups of the carbohydrates, followed by colour development as the o-phenanthroline complex. All sugars tested produced an equal colour yield. The method proved to be reproducible and precise with a high degree of sensitivity which makes it possible to use with small sample quantities. The method is quick, easy and cheap, hence permiting its use in routine analysis.

Applied Nonparametric Statistical Method

Chapter

Jan 1989

Peter Sprent

When we have two independent samples and wish to compare their location (medians or means) we can no longer reduce this to a one-sample problem.

Forest litter production, chemistry, and decomposition following two years of free-air CO2 enrichment

Article

Feb 2001

Increases in tree biomass may be an important sink for CO2 as the atmospheric concentration continues to increase. Tree growth in temperate forests is often limited by the availability of soil nutrients. To assess whether soil nutrient limitation will constrain forest productivity under high atmospheric CO2, we studied the changes in forest litter production and nutrient cycling in a maturing southern U.S, loblolly pine-hardwood forest during two years of free-air CO2 enrichment. The objective of this paper is to present data on the chemistry of green leaves and leaf litter, nutrient-retranslocation efficiency, aboveground litter production, whole-system nutrient-use efficiency, decomposition, and N availability in response to forest growth under elevated CO2. The chemical composition of green leaves and leaf litter was largely unaffected by elevated CO2. Green-leaf nitrogen (N) and phosphorus (P) concentrations were not significantly lower under elevated CO2. N and P retranslocation from green leaves did not increase under elevated CO2; therefore, leaf litter N and P concentrations were not significantly lower under elevated CO2. The concentrations of carbon, lignin, and total nonstructural carbohydrates in litter were not significantly different under elevated CO2. Total aboveground litterfall increased significantly with CO2 fumigation, The increase in litterfall was due to significant increases in loblolly pine leaf litter and bark production. The mass of leaves from deciduous species did not increase with CO2 fumigation, Whole-system nutrient-use efficiency (aboveground litterfall/nutrient content of litterfall) did not increase as a consequence of forest growth under elevated CO2, but N and P fluxes from vegetation to the forest floor increased significantly. During the second year of CO2 fumigation, the flux of N and P to the forest floor in litterfall increased by 20% and 34%, respectively. The rate of mass loss during one year of decomposition was unaffected by "litter type" (whether the litter was produced under ambient or elevated CO,), nor by the "site" of decomposition (whether the litter was decomposed in the ambient or elevated CO, plots). N was immobilized in litter during decomposition, whereas P was mineralized. There was no consistent effect of litter type or site on nutrient dynamics in decomposing litter. There was no significant effect of elevated CO2 on the pool size of inorganic N (NH4+ and NO3-) in the top 7.5 cm of mineral soil. The rate of net N mineralization and nitrification in mineral soil was not significantly different between treatment and control plots. Identifying the source of the nutrients lost in litterfall is critical to the long-term potential growth Stimulation of forests under elevated CO2. If the nutrients lost from biomass come from storage (e.g., the movement of nutrients from wood to leaves), then the increase in litter production should decrease over time as slowly replenished nutrient reserves are exhausted. If the nutrients lost in plant litter are replaced by uptake from soils, then it is possible (1) that trees acquire soil nutrients at a rate commensurate with growth stimulated by elevated CO2; and (2) that forest productivity will be stimulated by elevated CO2 in the long term.

Decomposition in Terrestrial Ecosystems. Studies in Ecology Vol. 5.

Article

Mar 1981

The Effects of Climate Change on Decomposition Processes in Grassland and Coniferous Forests

Article

Aug 1991

J. M. Anderson

Current models of climate change predict a reduction of area covered by northern coniferous forests and tundra, and an increase in grasslands. These scenarios also indicate a northerly shift in agricultural regions, bringing virgin soils under cultivation. The direct effects of man on tundra, boreal forest, and temperate grassland ecosystems are likely to result in less carbon mobilization from soils and vegetation than from tropical forests. However, as a consequence of climate change, carbon mineralization rates from arctic and sub-arctic soils could be very rapid under warmer and drier conditions because of low stabilization of soil organic matter (SOM) and enhanced microbial responses to small changes in soil moisture and temperature. Predicting the response of these systems to climate change is complicated where the edaphic environment regulating SOM dynamics is not a direct function of macroclimatic conditions. The primary recommendation for future research is for integrated studies on plant and soil processes. -from Author

Responses of Three Saturniid Species to Paper Birch Grown Under Enriched CO 2 Atmospheres

Article

Apr 1995

1. Interactions between trees and tree-feeding insects are likely to shift under conditions of enriched atmospheric CO2 owing to changes in foliar chemical composition. This study addressed the effects of CO2-mediated changes in leaf chemistry on performance of three silkmoth (Saturniidae) species: cecropia (Hyalophora cecropia), luna (Actias luna) and polyphemus (Antheraea polyphemus polyphemus). 2. Growth under elevated CO2 atmospheres decreased nitrogen concentrations (23%) but tripled starch and doubled condensed tannin concentrations, resulting in a marked increase in foliar carbon:nitrogen ratio. 3. Survival of first stadium larvae was marginally reduced when reared on high CO2 leaves. 4. Development rates were prolonged, growth rates tended to decline, consumption increased and food processing efficiencies decreased for fourth stadium larvae reared on high CO2 leaves. The magnitude of responses varied among species. 5. Overall performance of these saturniid species, at least when feeding on birch, is predicted to decline under atmospheric CO2 conditions anticipated for the next century.

Carbon/Nutrient Balance of Boreal Plants in Relation to Vertebrate Herbivory

Article

May 1983

The evolutionary response of plants to herbivory is constrained by the availability of resources in the environment. Woody plants adapted to low-resource environments have intrinsically slow growth rates that limit their capacity to grow rapidly beyond the reach of most browsing mammals. Their low capacity to acquire resources limits their potential for compensatory growth which would otherwise enable them to replace tissue destroyed by browsing. Plants adapted to low-resource environments have responded to browsing by evolving strong constitutive defenses with relatively low ontogenetic plasticity. Because nutrients are often more limiting than light in boreal forests, slowly growing boreal forest trees utilize carbon-based rather than nitrogen-based defenses. More rapidly growing shade-intolerant trees that are adapted to growth in high-resource environments are selected for competitive ability and can grow rapidly beyond the range of most browsing mammals. Moreover, these plants have the carbon and nutrient reserves necessary to replace tissue lost to browsing through compensatory growth. However, because browsing of juvenile plants reduces vertical growth and thus competitive ability, these plants are selected for resistance to browsing during the juvenile growth phase. Consequently, early successional boreal forest trees have responded to browsing by evolving strong defenses during juvenility only. Because severe pruning causes woody plants to revert to a juvenile form, resistance of woody plants to hares increases after severe hare browsing as occurs during hare population outbreaks. This increase in browsing resistance may play a significant role in boreal forest plant-hare interactions. Unlike woody plants, graminoids retain large reserves of carbon and nutrients below ground in both low-resource and high-resource environments and can respond to severe grazing through compensatory growth. These fundamental differences between the response of woody plants and graminoids to vertebrate herbivory suggest that the dynamics of browsing systems and grazing systems are qualitatively different. /// Эволюционная реакция растений на выедание фитофагами органичивается дос-тупностью ресурсов в природной среде. Древесые растения, адаптированные к местообитаниям с низкнм количеством ресурсов, имеют эндогенные низкие темпы роста, что лимитирует их способность к быстрому росту после повреж-дения мпекопитающими, обьедающими побеги. Их низкая способность к утили-зации ресурсов ограничивает их потенцию к компенсаторному росту, возме-щающему ткани, поврежденные при обьедании побегов. Растения, адаптирован-ные к местообитаниям с низким запасом ресурсов, реагируют на повреждения развитием сильных конструктивных защитных механизмов с относительно низ-кой онтогенетической пластичностью. Так как элементы питания часто более ограничены, чем освещение в бореальных лесах, медленно растущие деревья бореальных лесов используют защитные механизмы, основанные чаще на угле-родных, нежели азотных соединениях. У быстрее растущих деревьев, чувстви-тельных к затенеию, которые адаптированы к росту в более обеспеченных ре-сурсами местообитаниях, отбор был направлен на конкурентоспособность, они могут быстро расти после повреждений большинства млекопитакщих, обьедаю-щих побеги. Голее того, эти растения имеют резервы углерда и азота, не-обходимые для замещения обьеденных тканей в процессе компесаторного роста. Однако, так как обьедание молодых растений снижает их вертикальный рост и таким образом конкурентоспособность у этих растений отбор направлен на устойчивость к обьеданию в течение ювенильной фазы роста. Следовательно, деревья бореальных лесов ранний сукцессионной реагируют на обьеда-ние рзвитием сильных защитных механизмов лишь в незрелом состоянии. Так как сильное обьедание возращает древесные растения к ювенильной форме, у-стойчивость древесных растений к повреждениям зайцев поьшается после сильного обьедания зайцами, как это наблюдалось в периоды вспышек числен-ности их популяций. Это повышение устойчивости к обьеданию может играть существенную роль в отношениях растение-заяц, в бореальных лесах. В отли-чие от древесных растений, злаковые сохраняют резервы углерода и других элементов в подземных частях в местообитаниях с низкой и высокой обеспе-ченностью ресурсами и могут реагировать на сильный выпас компенсаторным ростом. Эти функциональные различия между реакцией древесных растений и злаков на выедание млекопитаюшими показывает, что динамика систем обгла-дывания и пастьбы качественно различны.

The Characterization of Ozone Data for Sites Located in Forested Areas of the Eastern United States

Article

Sep 1987
J Air Pollut Contr Assoc

Six years (1978-1983) of ozone monitoring data from sites located within six forested areas were examined. Areas that experienced the lowest to the highest ozone exposures were located in (1) northern New England/New York and upper Great Lakes, (2) New York/Pennsylvania/Maryland, (3) southeastern/southern, and (4) New Jersey pinelands. In general, higher ozone concentrations were observed in 1978, 1980 and 1983 as compared to the other three years examined. Ozone concentrations varied considerably within the areas. Recommendations for additional ozone monitoring sites are made. A concentrated effort should be made to examine ozone monitoring data from subsequent years (1984, 1985, and 1986) to explore whether the 6-year period 1978 through 1983 is representative of the annual variability of ozone concentrations over eastern forested areas. To better understand the relationship between ozone exposure and possible forest effects, we recommend that the temporal distributions of elevated ozone concentrations over a growing season be examined. The occurrence of elevated ozone levels during specific growth periods during a season may be an important aspect that biologists may wish to explore.

Genotypic variation for condensed tannin production in trembling aspen ( POPULUS TREMULOIDES, salicaceae) under elevated CO 2 and in high- and low-fertility soil

Article

Aug 1999

The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO 2 partial pressure and high- and low-fertility soil in field open-top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO2 and low soil fertility compared to ambient CO2 and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO2, while others showed no CO2 response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO2, and fertility treatments. These results suggest that with rising atmospheric CO 2, plant secondary compound production may vary within species. This could have consequences for plant‐herbivore and plant‐microbe interactions and for the evolutionary response of this species to global climate change.

Effects of CO2 and light on tree phytochemistry and insect performance

Article

Feb 2000
OIKOS

Direct and interactive effects of CO 2 and light on tree phytochemistry and insect fitness parameters were examined through experimental manipulations of plant growth conditions and performance of insect bioassays. Three species of deciduous trees (quaking aspen, Populus tremuloides ; paper birch, Betula papyrifera ; sugar maple, Acer saccharum ) were grown under ambient (387±8 μL/L) and elevated (696±2 μL/L) levels of atmospheric CO 2 , with low and high light availability (375 and 855 μmol×m ⁻² ×s ⁻¹ at solar noon). Effects on the population and individual performance of a generalist phytophagous insect, the white‐marked tussock moth ( Orgyia leucostigma ) were evaluated. Caterpillars were reared on experimental trees for the duration of the larval stage, and complementary short‐term (fourth instar) feeding trials were conducted with insects fed detached leaves. Phytochemical analyses demonstrated strong effects of both CO 2 and light on all foliar nutritional variables (water, starch and nitrogen). For all species, enriched CO 2 decreased water content and increased starch content, especially under high light conditions. High CO 2 availability reduced levels of foliar nitrogen, but effects were species specific and most pronounced for high light aspen and birch. Analyses of secondary plant compounds revealed that levels of phenolic glycosides (salicortin and tremulacin) in aspen and condensed tannins in birch and maple were positively influenced by levels of both CO 2 and light. In contrast, levels of condensed tannins in aspen were primarily affected by light, whereas levels of ellagitannins and gallotannins in maple responded to light and CO 2 , respectively. The long‐term bioassays showed strong treatment effects on survival, development time, and pupal mass. In general, CO 2 effects were pronounced in high light and decreased along the gradient aspen birch maple. For larvae reared on high light aspen, enriched CO 2 resulted in 62% fewer survivors, with increased development time, and reduced pupal mass. For maple‐fed insects, elevated CO 2 levels had negative effects on survival and pupal mass in low light. For birch, the only negative CO 2 effects were observed in high light, where female larvae showed prolonged development. Fourth instar feeding trials demonstrated that low food conversion efficiency reduced insect performance. Elevated levels of CO 2 significantly reduced total consumption, especially by insects on high light aspen and low light maple. This research demonstrates that effects of CO 2 on phytochemistry and insect performance can be strongly light‐dependent, and that plant responses to these two environmental variables differ among species. Overall, increased CO 2 availability appeared to increase the defensive capacity of early‐successional species primarily under high light conditions, and of late‐successional species under low light conditions. Due to the interactive effects of tree species, light, CO 2 , and herbivory, community composition of forests may change in the future.

Does ozone change the primary or secondary metabolites of birch (Betula pendula Roth)

Article

Apr 1994
NEW PHYTOL

In field experiments three clones of two-year-old birch (Betula pendula Roth.) were exposed for one growing season to an ozone concentration 1–2 times higher than ambient. At the end of August, leaf and stem material was analyzed for a wide range of primary and secondary metabolites. Although most of these metabolites were not significantly affected by ozone exposure, ozone-treated leaves contained larger concentrations of total sugars and reduced amounts of the phenolic glucoside, dehydrosalidroside. In the stems, greater amounts of catechin pentoside, hyperoside and papyriferic acid were found. The results indicated considerable inter- and intra-clonal variation in the production of phytochemicals in both leaves and stems.

Growth responses of Populus tremuloides clones to interacting carbon dioxide and tropospheric ozone

Article

Jan 2001

A simple and sensitive method for determining reducing sugars in plant tissues. Application to quantify the sugar content in Quinoa (Chenopodium quinoa Willd.) seedlings

Article

Mar 1998
PHYTOCHEM ANALYSIS

The impact of elevated atmospheric CO2 on insect herbivores

Article

Jan 1995

Applied nonparametric statistical methods. 3rd ed

Article

Mar 1994

P. Sprent

CO2-Mediated Changes in Tree Chemistry and Tree-Lepidoptera Interactions

Chapter

Dec 1996

Richard L. Lindroth

The Role of Nitrogen in the Response of Forest Net Primary Production to Elevated Atmospheric Carbon Dioxide

Article

Nov 2003
Annu Rev Ecol Systemat

We review experimental studies to evaluate how the nitrogen cycle influences the response of forest net primary production (NPP) to elevated CO2. The studies in our survey report that at the tissue level, elevated CO2 reduces leaf nitrogen concentration an average 21%, but that it has a smaller effect on nitrogen concentrations in stems and fine roots. In contrast, higher soil nitrogen availability generally increases leaf nitrogen concentration. Among studies that manipulate both soil nitrogen availability and atmospheric C02, photosynthetic response depends on a linear relationship with the response of leaf nitrogen concentration and the amount of change in atmospheric CO2 concentration. Although elevated CO2 often results in reduced tissue respiration rate per unit biomass, the link to changes in tissue nitrogen concentration is not well studied. 1The US government has the right to retain a nonexclusive, royalty-free license in and to any copyright covering this paper.

Introduction to Linear Models and Experimental Design

Article

Mar 2012
TECHNOMETRICS

This text is designed for an introductory graduate level course in statistics and experimental design. While the text is oriented toward the behavioral sciences, it may be applicable to other settings as well—an undergraduate class in applied statistics or the medical sciences. Chapters 1 and 2 cover elementary probability and statistical inference, while Chapters 3 and 4 deal with the general linear model and the general linear hypothesis. Chapter 5 is an overview of experimental design. Chapters 6 through 8 contain more than 40 example applications of the univariate normal, multivariate normal, and multinomial analysis of variance models. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Rising CO2 levels and their potential significance for carbon flow in photosynthetic cells

Article

Apr 2006
PLANT CELL ENVIRON

Mark Stitt

In the first part of this review, I discuss how we can predict the direct short-term effect of enhanced CO2 on photosynthetic rate in C3 terrestrial plants. To do this, I consider: (1) to what extent enhanced CO2 will stimulate or relieve demand on partial processes like carboxylation, light harvesting and electron transport, the Calvin cycle, and end-product synthesis; and (2) the extent to which these various processes actually control the rate of photosynthesis. I conclude that control is usually shared between Rubisco (which responds sensitively to CO2) and other components (which respond less sensitively), and that photosynthesis will be stimulated by 25–75% when the CO2 concentration is doubled from 35 to 70 Pa. This is in good agreement with the published responses. In the next part of the review, I discuss the evidence that most plants undergo a gradual inhibition of photosynthesis during acclimation to enhanced CO2. I argue that this is related to an inadequate demand for carbohydrate in the remainder of the plant. Differences in the long-term response to CO2 may be explained by differences in the sink-source status of plants, depending upon the species, the developmental stage, and the developmental conditions. In the third part of the review, I consider the biochemical mechanisms which are involved in ‘sink’ regulation of photosynthesis. Accumulating carbohydrate could lead to a direct inhibition of photosynthesis, involving mechanical damage by large starch grains or Pi-limitation due to inhibition of sucrose synthesis. I argue that Pi is important in the short-term regulation of partitioning to sucrose and starch, but that its contribution to ‘sink’ regulation has not yet been conclusively demonstrated. Indirect or ‘adaptive’ regulation of photosynthesis is probably more important, involving decreases in amounts of key photosynthetic enzymes, including Rubisco. This decreases the rate of photosynthesis, and potentially would allow resources (e.g. amino acids) to be remobilized from the leaves and reinvested in sink growth to readjust the sink-source balance. In the final part of the review, I argue that similar changes of Rubisco and, possibly, other proteins are probably also involved during acclimation to high CO2.

Cotrufo MF, Ineson P, Scott A. Elevated CO2 reduces the nitrogen concentration of plant tissues. Global Change Biology

Article

Jan 2002
GLOBAL CHANGE BIOL

We summarize the impacts of elevated CO2 on the N concentration of plant tissues and present data to support the hypothesis that reductions in the quality of plant tissue commonly occur when plants are grown under elevated CO2. Synthesis of existing data showed an average 14% reduction of N concentrations in plant tissue generated under elevated CO2 regimes. However, elevated CO2 appeared to have different effects on the N concentrations of different plant types, as the reported reductions in N have been larger in C3 plants than in C4 plants and N2-fixers. Under elevated CO2 plants changed their allocation of N between above- and below-ground components: root N concentrations were reduced by an average of 9% compared to a 14% average reduction for above-ground tissues. Although the concentration of CO2 treatments represented a significant source of variance for plant N concentration, no consistent trends were observed between them.

Ozone and forest trees

Article

May 1998
NEW PHYTOL

MARK BROADMEADOW

Current estimates of forest yield losses attributable to ozone pollution amount to c . 10% over Europe as a whole. This figure is derived from a synthesis of all European studies using trees for which AOT40 exposure values are available. However, the choice of 40 nl l ⁻¹ as the threshold concentration for demonstrable effects has led to debate, and this value might not be low enough to predict ozone effects in Scandinavia, where concentrations are lower than in southern Europe, and chronic injury resulting from cumulative exposure is observed. This ‘level I’ approach provides a useful means for mapping physiologically effective concentrations but has significant shortcomings in that it is unable to take environmental conditions into account. In order to produce a mechanism capable of predicting yield losses resulting from ozone pollution at specific sites and for individual species, the effective ozone dose, a product of conductance and concentration, must be calculated. Process‐based models relating the environment (temperature, humidity/saturation deficit, incident light and soil moisture content) to conductance are available for a number of species (oak, Scots pine, Norway spruce, Sitka spruce, beech and poplar). Effective ozone doses could therefore be calculated, and the relationships between effective dose and yield loss could be determined by revisiting existing data for which only concentrations or AOT40 values are available at present. Yield loss must be the growth parameter with which ozone damage is expressed, since visible injury does not necessarily represent severe injury to the plant, whilst visibly unaffected plants may be significantly compromised in terms of biomass accumulation. For conifers, premature needle drop, although indicative of ozone pollution, might not represent a significant reduction in growth since older needles are, functionally, relatively unimportant. When revisiting old experiments the question should also be asked ‘what is an appropriate control treatment’. It is unrealistic to expect ambient O 3 concentrations on a global scale to return to pre‐industrialization levels, and therefore the use of a charcoal‐filtered treatment is probably unrealistic. In addition, charcoal filters will remove some of the NO x , and therefore on nutrient deficient soils (typical of many forest soils) the ‘control’ treatment might represent a reduced supply of nitrogen, making it difficult to disentangle the ozone effect per se . The stage has therefore been reached where ‘level II’ ozone exposure mapping (i.e. based on effective dose at the physiological level) is possible for a number of species. As financial considerations become increasingly important, the scientific community must aim to provide better estimates of O 3 ‐induced yield losses so that long‐term environmental audits can be performed.

A meta-analysis of elevated CO2 effects on woody plant mass, form, and physiology

Article

Jan 1998

Quantitative integration of the literature on the effect of elevated CO2 on woody plants is important to aid our understanding of forest health in coming decades and to better predict terrestrial feedbacks on the global carbon cycle. We used meta-analytic methods to summarize and interpret more than 500 reports of effects of elevated CO2 on woody plant biomass accumulation and partitioning, gas exchange, and leaf nitrogen and starch content. The CO2 effect size metric we used was the log-transformed ratio of elevated compared to ambient response means weighted by the inverse of the variance of the log ratio. Variation in effect size among studies was partitioned according to the presence of interacting stress factors, length of CO2 exposure, functional group status, pot size, and type of CO2 exposure facility. Both total biomass (W T) and net CO2 assimilation (A) increased significantly at about twice ambient CO2, regardless of growth conditions. Low soil nutrient availability reduced the CO2 stimulation of W T by half, from +31% under optimal conditions to +16%, while low light increased the response to +52%. We found no significant shifts in biomass allocation under high CO2. Interacting stress factors had no effect on the magnitude of responses of A to CO2, although plants grown in growth chambers had significantly lower responses (+19%) than those grown in greenhouses or in open-top chambers (+54%). We found no consistent evidence for photosynthetic acclimation to CO2 enrichment except in trees grown in pots <0.5 l (−36%) and no significant CO2 effect on stomatal conductance. Both leaf dark respiration and leaf nitrogen were significantly reduced under elevated CO2 (−18% and −16% respectively, data expressed on a leaf mass basis), while leaf starch content increased significantly except in low nutrient grown gymnosperms. Our results provide robust, statistically defensible estimates of elevated CO2 effect sizes against which new results may be compared or for use in forest and climate model parameterization.

The influence of elevated CO2 and O3 concentrations on Scots pine needles: Changes in starch and secondary metabolites over three exposure years

Article

May 1998

Scots pine (Pinus sylvestris L.) trees, aged about 20 years old, growing on a natural pine heath were exposed to two concentrations of CO2 (ambient CO2 and double-ambient CO2) and two O3 regimes (ambient O3 and double-ambient O3) and their combination in open-top chambers during growing seasons 1994, 1995 and 1996. Concentrations of foliar starch and secondary compounds are reported in this paper. Starch concentrations remained unaffected by elevated CO2 and/or O3 concentrations during the first 2 study years. But in the autumn of the last study year, a significantly higher concentration of starch was found in current-year needles of trees exposed to elevated CO2 compared with ambient air. There were large differences in concentrations of starch and secondary compounds between individual trees. Elevated concentrations of CO2 and/or O3 did not have any significant effects on the concentrations of foliar total monoterpenes, total resin acids or total phenolics. Significantly higher concentrations of monoterpenes and resin acids and mostly lower concentrations of starch were found in trees growing without chambers than in those growing in open-top chambers, while there were no differences in concentrations of total phenolics between trees growing without or in chambers. The results suggest that elevated concentrations of CO2 might increase foliar starch concentrations in Scots pine, while secondary metabolites remain unaffected. Realistically elevated O3 concentrations do not have clear effects on carbon allocation to starch and secondary compounds even after 3 exposure years.

The conversion of procyanidins to prodelphinidins to cyanidin and delphinidin

Article

Dec 1985
PHYTOCHEMISTRY

The hydrolysis of proanthocyanidins to anthocyanidins in n-BuOH-HCl (95:5) has been shown to be an autoxidation, the yield of anthocyanidin being critically dependent on trace metal-ion impurities. Reproducible yields of anthocyanidin may be achieved if iron (III) salts are added to the reaction medium, and a standard method of analysis of proanthocyanidins based on use of an n-BuOH-HCl-FeIII mixture is given. The ratio of absorbance maxima of the cyanidin (550 nm) produced to that near 280 nm for the original procyanidin polymer solution was ∼ 3.5.

Effects of genotype and nutrient availability on phytochemistry of trembling aspen (Populus tremuloides Michx.) during leaf senescence

Article

Apr 2002
BIOCHEM SYST ECOL

We documented temporal patterns in phytochemical composition of Populus tremuloides Michx. during leaf senescence, and the influence of genotype and soil nutrient availability on such patterns. Levels of foliar nitrogen, carbohydrates, phenolic glycosides and condensed tannins were quantified for four aspen genotypes grown in a common garden, with low and high levels of soil nutrients. Levels of all compounds tended to decline over time, although the magnitude of change was influenced by plant genotype and nutrient availability. Genetic variation in concentrations of phytochemicals was much greater for phenolic glycosides and tannins than for nitrogen and carbohydrates, and these phenolic signatures generally persisted through leaf abscission. Our results suggest that genotypic and nutrient effects on patterns of chemical change during senescence will likely influence the performance of late-season herbivores on aspen. Moreover, nutrient and especially genotypic variation in phytochemistry of abscised leaves is likely to affect litter decomposition rates.

The Dilemma of Plants: To Grow or Defend

Article

Sep 1992

Physiological and ecological constraints play key roles in the evolution of plant growth patterns, especially in relation to defenses against herbivores. Phenotypic and life history theories are unified within the growth-differentiation balance (GDB) framework, forming an integrated system Of theories explaining and predicting patterns of plant defense and competitive interactions in ecological and evolutionary time. Plant activity at the cellular level can be classified as growth (cell division and enlargement) of differentiation (chemical and morphological changes leading to cell maturation and specialization). The GDB hypothesis of plant defense is premised upon a physiological trade-off between growth and differentiation processes. The trade-off between growth and defense exists because secondary metabolism and structural reinforcement are physiologically constrained in dividing and enlarging cells, and because they divert resources from the production of new leaf area. Hence the dilemma of plants:

Can elevated CO2 affect secondary metabolism and ecosystem function? Trend Ecol Evol

Article

Jan 1998
TRENDS ECOL EVOL

It has generally been assumed that increasing atmospheric CO2 concentrations will increase plant carbon-based secondary or structural compounds concentrations. These changes may have far-reaching consequences for herbivory and plant litter decomposition. Recent experimental results provide evidence of increases in concentrations of soluble phenolics and condensed tannins but not in lignin, structural polysaccharides or terpenes. They also show significant effects of these plant chemical changes on herbivores and little or any effects on decomposition. However, there is no consistent evidence of any of these effects at the complex long-term ecosystem level.

The effect of elevated CO2 and fertilization on primary and secondary metabolites in birch Betula pendula (Roth)

Article

Sep 1994

Seedlings of European white birch (Betula pendula Roth) were grown in growth chambers for one growth season under four carbon dioxide regimes (350, 700, 1050 and 1400 ppm) and at three fertilization levels (0, 100 and 500 kg ha−1 monthly). The soluble carbohydrates and secondary phenolics in the leaves and stems were analysed. It was found that fertilizer addition reduced the amounts of glucose and fructose while sucrose remained almost unaffected. The sugar content of leaves increased at 700 ppm and 1050 ppm of CO2 and decreased at the highest CO2 concentration (1400 ppm). The amounts of proanthocyanidins and flavonoids in leaves decreased with fertilization addition and increased with CO2 enrichment. The production of simple phenolic glucosides varied according to the fertilization and CO2 treatments. The triterpenoid content of stems seemed to increase with fertilization and CO2-addition. Our results indicate that the production of phytochemicals in the birch seedlings is very sensitive to both fertilization and CO2 addition, which is in agreement with earlier studies, and thus provide some support for the hypothesis of carbon allocation to plant defence when there is an excess of carbon and nutrient. The considerable variation in the production of secondary components may indicate that the synthesis of these defensive metabolites can be regulated by a plant to certain extent, depending on the ability of the plant to acclimate to changes in the physical environment.

Changes in Growth, Leaf Abscission, and Biomass Associated With Seasonal Tropospheric Ozone Exposures of Populus Tremuloides Clones and Seedlings

Article

Feb 2011
CAN J FOREST RES

The effects of single-season tropospheric ozone (O3) exposures on growth, leaf abscission, and biomass of trembling aspen (Populustremuloides Michx.) rooted cuttings and seedlings were studied. Plants were grown in the Upper Peninsula of Michigan in open-top chambers with O3 exposures that ranged from 7 to 92 ppm-h. Depending on the genotype, total seasonal O3 exposure in the range of 50–92 ppm-h had negative impacts on stem, retained leaf, and root biomass accumulation and on diameter growth. Leaf abscission generally increased with increasing O3 exposure and was the principal cause of the decrease in leaf biomass of the O3-treated plants. Considerable genetic variation in O3 responses occurred, as shown by differences in sensitivities among clones and among seedlings. However, the responses to O3 of rooted cuttings and seedlings were similar when seedling means were compared with clonal means for leaf abscission, diameter growth, retained leaf biomass, and root biomass. Comparison of a single square-wave treatment (52 ppm-h) with 70 and 92 ppm-h episodic exposures suggested that the plant response to the square-wave exposure was similar to the response to the highest episodic exposure even though the 92 ppm-h episodic exposure was almost twice the square-wave exposure. Our results are consistent with previous studies that show that P. tremuloides is highly responsive to O3 exposure and this response has a strong genetic component.

Foliar senescence in an aspen ( Populus tremuloides ) clone: the response of element resorption to interramet variation and timing of abscission

Article

Aug 1990
CAN J FOREST RES

Nutrient movements in the senescing foliage of a Rhode Island aspen were measured. Mean resorption of N, P, and Cu was 43, 51 and 10%, respectively. Aluminium, B, Ca, Fe, Mg, Mn, and Zn increased or remained unchanged in senescing foliage during 1986. Resorption of N and P decreased, respectively, from 56 and 64% in 1986 to 24 and 38% in 1988. Resorption of N and P decreased, respectively, from 56 and 64% in 1986 to 24 and 38% in 1988. Older, larger ramets resorbed less N and Cu. Timing of abscission strongly influenced resorption and may have been related to drought conditions in 1988 and to differential exposure to wind in all years. Resorption of N, P and Cu was lowest in those ramets that lost their leaves earliest and in leaves that senesced earliest on individual ramets. -from Authors

Enriched atmospheric CO2 and defoliation: Effects on tree chemistry and insect performance

Article

Apr 1998

Abstract We examined the effects of CO2 and defoliation on tree chemistry and performance of the forest tent caterpillar, Malacosoma disstria. Quaking aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees were grown in open-top chambers under ambient or elevated concentrations of CO2. During the second year of growth, half of the trees were exposed to free-feeding forest tent caterpillars, while the remaining trees served as nondefoliated controls. Foliage was collected weekly for phytochemical analysis. Insect performance was evaluated on foliage from each of the treatments. At the sampling date coincident with insect bioassays, levels of foliar nitrogen and starch were lower and higher, respectively, in high CO2 foliage, and this trend persisted throughout the study. CO2-mediated increases in secondary compounds were observed for condensed tannins in aspen and gallotannins in maple. Defoliation reduced levels of water and nitrogen in aspen but had no effect on primary metabolites in maple. Similarly, defoliation induced accumulations of secondary compounds in aspen but not in maple. Larvae fed foliage from the enriched CO2 or defoliated treatments exhibited reduced growth and food processing efficiencies, relative to larvae on ambient CO2 or nondefoliated diets, but the patterns were host species-specific. Overall, CO2 and defoliation appeared to exert independent effects on foliar chemistry and forest tent caterpillar performance.

Condensed tannin purification and characterization of tannin-associated protein

Article

May 1980

The conventional isolation method has been modified in order to minimize protein contamination of tannin purified from high tannin sorghum. The two unique steps of the new procedure are preliminary extraction of the ground grain with ethanol and treatment of the partially purified tannin with phenol to remove traces of noncovalently bound protein. Tannin-associated protein removed by phenol treatment is not a random mixture of all the seed proteins, but consists of several discrete components which have been isolated and partially characterized. These proteins are quite hydrophobic, and one is rich in proline. With only minor changes, the purification method can be used to isolate tannin from seeds of other plants such as legumes.

Growth responses of Populus tremuloides clones to interacting elevated carbon dioxide and tropospheric ozone

Article

Feb 2001
ENVIRON POLLUT

The Intergovernmental Panel of Climate Change (IPCC) has concluded that the greenhouse gases carbon dioxide (CO2) and tropospheric ozone (O3) are increasing concomitantly globally. Little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. In this study we assess the effects of three successive years of exposure to combinations of elevated CO2 and O3 on growth responses in a five trembling aspen (Populus tremuloides) clonal mixture in a regenerating stand. The experiment is located in Rhinelander, Wisconsin, USA (45°N 89°W) and employs free air carbon dioxide and ozone enrichment (FACE) technology. The aspen stand was exposed to a factorial combination of four treatments consisting of elevated CO2 (560 ppm), elevated O3 (episodic exposure-90 μ1 1−1 hour−1), a combination of elevated CO2 and O3, and ambient control in 30 m treatment rings with three replications.

Consequences of elevated carbon dioxide and ozone for foliar chemical composition and dynamics in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera)

Abstract

No full-text available

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Independent, Interactive, and Species-Specific Responses of Leaf Litter Decomposition to Elevated CO...