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Evaporative demand determines branchiness of Scots pine
Abstract
Analysis of the branch area/stem area ratio of Scots pine growing in different climatic conditions in Europe and Siberia indicates that the branch area supported by a stem increases in warmer and drier conditions. The ratio was significantly correlated with several climatic variables, especially with potential evapotranspiration (E
p). The ratio was negatively correlated with stand density (d
s). A regression model combining E
p and d
s accounted for 85% of the total variation. These trends are believed to reflect hydraulic segmentation of trees and may represent a strategy to avoid cavitation in the tree, especially in the branches.
... Zinātniskajā literatūrā ir plaši diskutēts par koku virszemes un celma/sakņu biomasas mainību pat vienas sugas ietvaros, secinot, ka sagaidāmo biomasu ietekmē, piemēram, veģetācijas zonas, platuma grādi, ūdens deficīts, gada vidējā temperatūra un citi faktori (Berninger et al., 1995;Stegen et al., 2011;Wirth et al., 2004;u. c.). ...
... Šo pārrēķina koeficientu lietošana Latvijas mežos var radīt ievērojamu uzkrātā oglekļa pārvērtēšanas risku. Vairāki zinātnieki ir pētījuši koku virszemes biomasas variēšanu atkarībā no ģeogrāfiskā novietojuma, veģetācijas zonām, ūdens deficīta, vidējās temperatūras un citiem faktoriem (Berninger et al., 1995;Wirth et al., 2004;Stegen et al., 2011). Dažādu klimatisko faktoru kompleksās iedarbības rezultātā mežaudžu krājai, līdz ar to arī kokos uzkrātā oglekļa apjomam Eiropā ir tendence palielināties virzienā no ziemeļu platuma grādiem uz dienvidiem. ...
... Pētījuma rezultāti sakrīt ar A. Smith et al. (2016) secinājumiem, ka biomasas vienādojumu ģeogrāfiska ekstrapolācija rada kļūdainus biomasas aprēķinus. Daudzi zinātnieki ir pētījuši AGB un BGB izmaiņas atkarībā no dažādiem faktoriem, secinot, ka koku biomasa ir atkarīga no ģeogrāfiskā platuma un garuma, veģetācijas zonas, ūdens deficīta, gada vidējās temperatūras un citiem faktoriem (Berninger et al., 1995;Wirth et al., 2004;Stegen et al., 2011). Koku augšanas apstākļi Zviedrijas dienvidos ir diezgan līdzīgi augšanas apstākļiem Latvijā un pēc teritoriālā novietojuma ietilpst Eiropas hemiboreālā mežu joslā (Ahti et al., 1968;EEA, 2007). ...
The present publication is a revised version of the PhD thesis “Methodology development for forest stand biomass and carbon stock estimates in Latvia”. Supervisors Dr.silv. Kaspars Liepiņš and Dr.silv. Andis Lazdiņš.Regardless the importance of the forestry sector in Latvia, the methodological basis for analysing the amount of biomass and sequestrated carbon in Latvia is still incomplete. Currently, one of the biggest drawbacks is that there are no approved and suitable biomass equations for common tree species in Latvia. Previous studies in Latvia on biomass and carbon assessment for common tree species are fragmented and limited to separate biomass fractions and several tree species. To estimate CO2 sequestration in aboveground and belowground woody biomass, accurate methods are required. This study is aimed to develop the methods for forest biomass and carbon stock assessment that are based on recommendations for national reporting.The material for study of aboveground and belowground tree biomass is collected in 124 forest stands. Three sample trees per stand have been harvested – in total 102 Scots pines, 81 Norway spruces, 105 birches and 84 European aspens, while stumps and roots of 37 Scots pines, 29 Norway spruces, 42 birches and 33 European aspens are lifted for belowground biomass studies. Accurate measurements of the stem basic density are needed to calculate total stem biomass. 14 366 stem wood and 4652 stem bark samples have been analysed to study the variation of within-the-stem basic density and to calculate the mean density of the stems.Our study approved that the basic density of stem bark significantly (p < 0.001) differs from stem wood density. The use of mean stem wood density values instead of whole stem density values leads to biased estimation of stem biomass (1.5–4.5% error depending on tree species). Examination of small root (diameter over 2 mm) biomass performed in our study to such an extent has not been done before. Within our study new equations for estimation of stem, branch, total aboveground and belowground biomass were developed for application in Latvian conditions for a wide range of tree dimensions. We found that the use of biomass equations applied for biomass estimation in Fennoscandia in our conditions are creating an 4.7–61.7% error depending on tree species and biomass component. Application of default values of biomass expansion factors and root to shoot ratios for temperate and boreal forests defined in IPCC guidelines creates an overestimation of 36.9% and an underestimation of 5.2%, respectively in comparison to methodology elaborated and recommended in this study. In accordance to the forest land definition used in national GHG reports, the total carbon stock in Latvia in year 2016 was 238.1 ±3.5 million tonnes.
... A final aim was to test for shifts in biomass distribution with climate. Little is known about global-scale patterns in biomass distribution in relation to climate, but one might expect biomass distribution to shift with precipitation or mean annual temperature, as small-scale comparisons have shown such responses (Callaway et al., 1994;Berninger et al., 1995;DeLucia et al., 2000;Poyatos et al., 2007). also showed that after controlling for the large size-related variation in biomass distribution, the ratio of leaf to total plant mass (averaged across whole stands, either including or excluding below-ground components) increases with mean annual temperature in both gymnosperms and angiosperms. ...
... The result that A F /A S did not correlate with climate seems to contradict reports, from studies on one or few species, that the ratio of sapwood area to leaf area (the 'Huber value') varies across climate gradients as quantified by summer evaporative demand (DeLucia et al., 2000;Poyatos et al., 2007), rainfall and temperature (Callaway et al., 1994), and temperature (Berninger et al., 1995). Possible reasons for the discrepancy include the following: we studied A S including the sapwood and heartwood; small-scale climate effects may have been present in our dataset but average out on large climate gradients; climate effects may be highly species-specific; and the majority of reported correlations between the Huber value and climate were for species in the genus Pinus. ...
Here, we aim to understand differences in biomass distribution between major woody plant functional types ( PFT s) (deciduous vs evergreen and gymnosperm vs angiosperm) in terms of underlying traits, in particular the leaf mass per area (LMA) and leaf area per unit stem basal area.
We used a large compilation of plant biomass and size observations, including observations of 21 084 individuals on 656 species. We used a combination of semiparametric methods and variance partitioning to test the influence of PFT , plant height, LMA, total leaf area, stem basal area and climate on above‐ground biomass distribution.
The ratio of leaf mass to above‐ground woody mass ( M F / M S ) varied strongly among PFT s. We found that M F / M S at a given plant height was proportional to LMA across PFT s. As a result, the PFT s did not differ in the amount of leaf area supported per unit above‐ground biomass or per unit stem basal area. Climate consistently explained very little additional variation in biomass distribution at a given plant size.
Combined, these results demonstrate consistent patterns in above‐ground biomass distribution and leaf area relationships among major woody PFTs, which can be used to further constrain global vegetation models.
... For example, larger crowns relative to the sapwood area result-if other tree parameters of the overall hydraulic conductivity remain the same-in lower water potentials and in a higher risk of cavitation (Maherali and de Lucia 2000;Cochard 2006;Ogasa et al. 2013). The Huber value (HV, Huber 1928;Tyree and Ewers 1991)-defined as the sapwood area supporting a unit amount of foliage-is therefore a good measure of tree adaptation to the environment and of the susceptibility of a tree to stress (e.g., Berninger et al. 1995;Poyatos et al. 2007, Martínez-Vilalta et al. 2009). Sapwood water storage is a key feature that helps the tree to cope with diurnal peaks in water demand as well as with a longer drought stress. ...
... The ratio of the needle biomass to the total crown biomass (40 %) was comparable to the fraction of 34 % reported by Monserud et al. (1996) for Scots pine in Russia. The HV is an indicator of the long-time hydraulic adjustment to local climatic conditions, also in Scots pine (e.g., Berninger et al. 1995;Poyatos et al. 2007;Martínez-Vilalta et al. 2009). Our observations on HV at breast height were in line with the values reported for Scots pine from a range of various sites (Mencuccini and Bonosi 2001;Poyatos et al. 2007) and were closer to drier sites (Martínez-Vilalta et al. 2009). ...
This study describes the amount and the spatial distribution of the above- and below-ground tree skeleton-defined as the woody structure of stem, branches and roots-in a mature Scots pine (Pinus sylvestris L.) stand in Belgium. Tree skeleton data were linked to the respective needle area, and as such, this work provides the background framework for modeling the tree hydraulic architecture and the carbon balance of the forest stand. Using validated allometric equations, we were able to calculate the amount of the volume, of the biomass and of the corresponding surface areas of individual trees in the stand. Total woody biomass of the 66-year-old forest stand was 155 Mg ha(-1), i.e., 126 Mg ha(-1) above ground and 29 Mg ha(-1) below ground. The total bio-volume of the woody mass of the stand was 314 m(3) ha(-1). The highest fraction of this value was the stem bio-volume, i.e., 236 m(3) ha(-1) or 75 % of the total. The total volume of all roots was 57 m(3) ha(-1) (18 % of the total volume), and the volume of branches was 20 m(3) ha(-1) (7 % of the total volume). The surface area of the roots ranged from 38,000 m(2) ha(-1) in the winter to 68,000 m(2) ha(-1) in the spring. The surface area of the stems was 2,700 m(2) ha(-1), and the surface area of all branches reached 4,400 m(2) ha(-1). The total above-ground water storage in the xylem was 94 m(3) ha(-1) (or 9.4 mm), while the accessible stored water was 2 mm of that quantity. A comparative analysis of the biometric parameters showed the balance between the different functionally connected, operational surface areas of the trees. The needle surface area was similar to the root surface area and in the same order of magnitude as the surface area of woody cambium. The results allow to link water uptake with transpiration and assimilation with respiration.
... Many authors have discussed variations in above-and belowground biomass across climatic and latitudinal gradients, concluding that tree biomass is affected by latitudinal gradients, vegetation zones, water deficit, annual temperature and other factors (e.g. Berninger et al. 1995;Wirth et al. 2004;Stegen et al. 2011). The growing conditions of south-central Sweden are similar to those of Latvia as they also represent the hemiboreal forest zone (Ahti et al. 1968;EEA 2007). ...
This study aims to derive allometric functions to estimate the above- and belowground biomass components of the most important tree species in Latvia. The study material included a total of 81 Norway spruce (Picea abies [L.] Karst), 102 Scots pine (Pinus sylvestris L.), 105 birch spp. (mainly silver birch (Betula pendula Roth)) and 84 European aspen (Populus tremula L.) trees sampled in 124 forest stands. The suitability of three mathematical models for the prediction of total aboveground biomass, stem biomass, total live and dead branch biomass, belowground biomass and small root biomass was evaluated. Our analysis revealed that the use of the Intergovernmental Panel on Climate Change (IPCC) mean default values for the root-to-shoot ratio recommended for temperate and boreal ecological zones leads to the overestimation of root biomass of young trees, especially Scots pine and Norway spruce. Our findings indicate that biomass functions recommended for other Baltic Sea countries are not appropriate for the assessment of the biomass stock in Latvia’s forests because these lead to biased estimates. The biomass functions derived in our study are recommended for reporting the biomass stock in Latvia.
... In addition, our study trees had limited variation in age, density, and tree size (Table 2), which further constrains potential variation compared to previous studies. Future study is required to determine how changes in branch A L :A S relate to whole tree A L :A S , as whole tree characteristics can be modified by canopy structure (Berninger et al., 1995) and stand development/tree size (Mencuccini & Bonosi, 2001;McDowell et al., 2002;Martinez-Vilalta et al., 2009) and represent an additional scale of hydraulic adjustment not measured here. ...
Range shifts are among the most ubiquitous ecological responses to anthropogenic climate change and have large consequences for ecosystems. Unfortunately, the ecophysiological forces that constrain range boundaries are poorly understood, making it difficult to mechanistically project range shifts. To explore the physiological mechanisms by which drought stress controls dry range boundaries in trees, we quantified elevational variation in drought tolerance and in drought avoidance-related functional traits of a widespread gymnosperm (ponderosa pine – Pinus ponderosa) and angiosperm (trembling aspen – Populus tremuloides) tree species in the southwestern USA. Specifically, we quantified tree-to-tree variation in growth, water stress (predawn and midday xylem tension), drought avoidance traits (branch conductivity, leaf/needle size, tree height, leaf area-to-sapwood area ratio), and drought tolerance traits (xylem resistance to embolism, hydraulic safety margin, wood density) at the range margins and range center of each species. Although water stress increased and growth declined strongly at lower range margins of both species, ponderosa pine and aspen showed contrasting patterns of clinal trait variation. Trembling aspen increased its drought tolerance at its dry range edge by growing stronger but more carbon dense branch and leaf tissues, implying an increased cost of growth at its range boundary. By contrast, ponderosa pine showed little elevational variation in drought-related traits but avoided drought stress at low elevations by limiting transpiration through stomatal closure, such that its dry range boundary is associated with limited carbon assimilation even in average climatic conditions. Thus, the same climatic factor (drought) may drive range boundaries through different physiological mechanisms – a result that has important implications for process-based modeling approaches to tree biogeography. Further, we show that comparing intraspecific patterns of trait variation across ranges, something rarely done in a range-limit context, helps elucidate a mechanistic understanding of range constraints.
The links between the hydraulic structure of the Pinus sylvestris trees, climate and stand characteristics were studied. Strong geographic variation was found in the ratio between the total cross-sectional areas of the branches and the stem below the living crown. Analysis indicated that the branch area supported by a stem increases in warmer and drier conditions, whereas the needle mass to branch area ratio seemed to be lower in the warmer conditions. The ratio of the branch and stem areas was positively correlated with yearly mean temperature, potential evapotranspiration and the length of the crown.
This chapter examines the effects of temperature stress and elevated CO2 on ecosystem processes, including primary production, nutrient cycling, and landscape water and energy balance. Environmental stress varies depending on whether it is applied to a cultivated production system or to an ecosystem. In its broadest sense, environmental stress is any factor that lowers primary production below its optimum. In this context, any nonoptimum temperature can be considered stressful. However, a more narrow view of environmental stress would require an environmental condition (for example, freezing/chilling temperatures, heat stress) to cause damage to plants. Severe damage to plants, causing either mortality or an irreversible loss in productivity, will have clear impacts on ecosystem processes. Also of interest from an ecosystem perspective is recurring environmental stress, which can result in either physiological hardening in plants (which may be irreversible within a given growing season) or genetic responses of populations over time, such that the ecosystem equilibrates to nonoptimum conditions through a loss of productivity. One important aspect of the global change debate is the potential rapidity with which global climate is predicted to change and its effects on ecological systems.
A five-year project, Crown-Fibre Attribute Relationships (CFAR), was completed by the Canadian Wood Fibre Centre (Natural Resources Canada) to explore the relationships between tree crown characteristics and wood fibre attributes. The CFAR project used a number of data sets distributed across Canada (e.g., silvicultural experiments), providing a range of crown conditions following spacing and thinning treatments. The approaches developed under the CFAR project, along with other relevant research, indicate that is possible to enhance current forest inventories by providing estimates of fibre attributes from crown characteristics of individual trees that can, or are poised to be, captured using remotely sensed data. Predictability was related to the dimensionality of the fibre attributes with models for zero-dimensionality fibre attributes (e.g., DBH) showing RMSE of 10% to 15% of mean values. Also, one-dimensional (e.g., sapwood area) and two-dimensional (i.e., ring area) models quantified longitudinal patterns with low bias. Current values of wood density were not related to crown characteristics; instead, recent research suggests that wood density is regulated by hydraulic and biomechanical constraints. Further evolution of remote sensing technology and related research will help to address the temporal problem posed by two-and three-dimensional fibre attributes.
This review presents a framework for evaluating how cells, tissues, organs, and whole plants perform both hydraulic and mechanical functions. The morphological alterations that affect dual functionality are varied: individual cells can have altered morphology; tissues can have altered partitioning to functions or altered cell alignment; and organs and whole plants can differ in their allocation to different tissues, or in the geometric distribution of the tissues they have. A hierarchical model emphasizes that morphological traits influence the hydraulic or mechanical properties; the properties, combined with the plant unit's environment, then influence the performance of that plant unit. As a special case, we discuss the mechanisms by which the proxy property wood density has strong correlations to performance but without direct causality. Traits and properties influence multiple aspects of performance, and there can be mutual compensations such that similar performance occurs. This compensation emphasizes that natural selection acts on, and a plant's viability is determined by, its performance, rather than its contributing traits and properties. Continued research on the relationships among traits, and on their effects on multiple aspects of performance, will help us better predict, manage, and select plant material for success under multiple stresses in the future.
Contents
Summary
747
I.
Introduction
747
II.
Studying dual functionality in plants: some conceptual approaches
749
III.
Mechanisms influencing dual functionality at different spatial scales
753
IV.
Conclusions
760
Acknowledgements
760
References
760
Mechanisms causing reduction of net assimilation by drought are: 1) stomatal closure reducing the net uptake of CO2 into leaves; 2) reduction of electron flow in photosystems I and II; and 3) disruption of enzyme activity thereby reducing the dark reactions of photosynthesis.-from Authors
Diagnostically illustrated with light and scanning electron micrographs, Comparative Wood Anatomy lucidly introduces dicotyledon wood in terms of cell types and their variations, pertinent literature, taxonomic distribution of features, terminology, and methods for preparation. Two final chapters present syntheses: taxonomic achievements of wood studies; and the evolutionary relationship between structure, physiological function, and ecology. This detailed survey serves a wide range of interests: identification, systematics, evolution and physiology.
Twelve wood anatornical characters, together with broad parameters from ecology, habit and phenology were subjected to simple correlation analysis, path analysis and principal component analysis, in a total sampie of over 470 specimens belonging to 271 species of the Rosaceae from the entire distribution area of the farnily. The functional, developmental and systematic implications of the resulting relations are discussed. Based on the present analysis of ecological trends and previous phylogenetic analysis, a tentative scenario for the evolution of the Rosaceae is offered.
The hydraulic architecture of trees is divided into segments of high and low hydraulic conductance. Segments of major stems are 50 to 1000 times more capable of supplying water to leaves down-stream than are minor branches. The functional advantages of plant segmentation are: 1) to allow all leaves to compete on a more or less equal basis for water resources in the canopy of large trees and 2) to confine xylem cavitations and embolisms to the minor branches during times of water stress.
Growth of trees is always restricted by drought stress. The mediating factor most often influencing growth response to drought is turgor pressure, because turgor pressure is the force causing plastic enlargement of cell walls. Low turgor can prevent the enlargement of cells to their full potential. Low turgor can also prevent meristematic cells from reaching the minimum size for cell division. Reduced shoot and leaf growth in one dry season can reduce the vigour and growth potential of trees for several subsequent years. Net assimilation of carbohydrates is also reduced by drought. The mechanisms causing reduction of net assimilation by drought are: (1) stomatal closure reducing the net uptake of CO2 into leaves, (2) reduction of electron flow in photosystems I and II and (3) disruption of enzyme activity thereby reducing the dark reactions of photosynthesis.
Coniferous trees, dicotyledonous trees, and dicotyledonous lianas (woody vines) form interesting morphological contrasts in their xylem structure and function. Lianas have among the largest (up to 8 metres or more) and widest (up to 500 µm) vessels in the plant kingdom. In conifers the water transport occurs through tracheids, which are relatively inefficient in transport. We can compare disparate growth forms in terms of leaf-specific. conductivity (LSC), which is hydraulic conductivity per surface area of leaves supplied by a stem. LSC is inversely proportional to localised pressure potential gradients. LSC is equal to the Huber value (sapwood area per leaf area supplied) times the specific conductivity (hydraulic conductivity per sapwood area). Lianas are similar to dicot trees and conifers in having hydraulic constrictions (low LSCs) at branch junctions. However, lianas generally have greater LSCs and specific conductivities but lower Huber values than do conifers. Dicot trees are intermediate in these values. The narrow but efficient stems of lianas are possible partly because lianas are not self-supporting; the mechanical requirements are reduced. Secondly, the wide and efficient vessels of lianas remain conductive for much longer than might be expected (two to several years, versus one year for similar wide vessels in dicots). Based upon experiments with glass capillary tubes and with living stem tissue, larger vessels are more susceptible to freezinginduced embolism than are small ones. However, in lianas, root pressures might serve to refill cavitated vessels on a daily or seasonal basis.
CONTENTS: INTRODUCTION; THE RADIATION BALANCE; SOIL HEAT FLUX AND SOIL TEMPERATURE; SENSIBLE HEAT FLUX, SURFACE AND AIR TEMPERATURE; WIND AND TURBULENT TRANSPORT; ATMOSPHERIC HUMIDITY; MODIFICATION OF THE SOIL TEMPERATURE REGIME; EVAPOTRANSPIRATION; PHOTOSYNTHESIS; CARBON DIOXIDE BALANCE; WINDBREAKS AND THE SHELTER EFFECT; FROST AND FROST CONTROL; IMPROVING WATER USE EFFICIENCY - SOME NEW METHODS; APPENDIX - NOTATION AND CUSTOMARY UNITS.