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Stand Biomass, Net Production and Canopy Structure in a Secondary Deciduous Broad-leaved Forest, Northern Japan
Abstract and Figures
II nn ss tt rr uu cc tt ii oo nn ss ff oo rr uu ss e 70 Research Em .~1 ~* 1&1 ntff)tZ1 ~ ~~1 mft mr~2 :.0* i£3 'lfm 5Ea 3 lip 7k;t;3 ~1t ~~3 Ili *1 Bni ~3 EfIJlj J;:PJ1 Abstract Stand biomass, net production and canopy structure were determined in a secondary deciduous broad-leaved forest (ca. 56 year·old) in the Tomakomai Experimental Forest of Hokkaido University, northern Japan, by felling all trees within a 10-m X 10-m plot. This forest was dominated by Quercus crispula and Phellodendron amurense at canopy layer, while Carpinus cordata and Sorb us alnifolia dominated in subcanopy layer. The maximum tree height and diameter were 16.7 m and 25.8 cm, respectively. Total above-and below-ground biomass of trees> 3.0 cm in trunk diameter was 130.4 t ha· 1 , and the ratio of above-to below-ground biomass was 5.16. Total above-ground net production was 6.13 t ha· 1 (2.47 t ha-1 by leaves and 4.15 t ha-1 by woody parts). Total leaf area of this stand was 5.1 ha ha· 1 with two peaks at herbs/saplings and canopy trees. Herbs occupied 84.1 % of leaf area at 0-2 m in height class. About 64% of total leaf area was concentrated in between the top of canopy (16.7 m) and 10 m from ground. Relative photosynthetic photon flux density was decreased in proportion to the cumulative leaf area from the top of canopy, while specific leaf area (leaf area per dry mass) was increased. The net production of leaves for each tree was linearly increased with tree height, while that of woody parts was exponentially increased. This suggests that the net production rate per leaf mass for the intermediate-sized trees was lower than that for saplings and canopy trees. Thus, the vertical profile of leaf distribution regulated the production and growth of trees through the distribution of available resources.
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... Our estimates are based on forest-level, above-ground oven-dry mass of main stem, branches and leaves (Table 2, Fig. 3). The data derive from four forests spanning a range of circumstances from equatorial to temperate, and include an old-growth mixed dipterocarp forest in Ulu Gadut, West Sumatra, Indonesia (Yoneda et al., 1990), a primary cooltemperate deciduous forest mixed with spruce in Tomakomai, central Hokkaido, Japan (Uraguchi and Kubo, 2005), a secondary cool-temperate deciduous forest in Tomakomai, Japan (Takahashi et al., 1999), and a subalpine spruce-fir forest on Mt. Onnebetsu in Shiretoko Mountains, eastern Hokkaido, Japan (Nishimura, 2006). ...
... Onnebetsu in Shiretoko Mountains, eastern Hokkaido, Japan (Nishimura, 2006). We used allometric equations specific to site/forest-type/life-form to estimate tree biomass from stem diameter (Niiyama et al., 2010;Nishimura, 2006;Takahashi et al., 1999). Appendix D provides further details about the plots, the data collection and the biomass estimation. ...
... This plot has 37 species (25 with ≥6 stems), where the abundant species include Acer mono (canopy), Cercidiphyllum japonicum (canopy), Acer amoenum (canopy), Picea jezoensis (canoy), Prunus ssiori (subcanopy), and Fraxinus lanuginosa (subcanopy). Fig. 3c shows estimates derived from a secondary cool-temperate deciduous forest (1 ha, 90 m a.s.l., 7.1°C mean temperature) that grew after clear-felling in 1941 in the Tomakomai Experimental Forest of Hokkaido University (Takahashi et al., 1999). The plot has 31 species (16 with ≥6 stems), dominated by Quercus crispula (canopy), Sorbus alnifolia (subcanopy), Acer mono (canopy), Fraxinus mandshurica (canopy) and Prunus sargentii (canopy early-successional). ...
NB the R code is here: https://data.mendeley.com/datasets/7sg66d9hmk/1
There is widespread interest in ensuring that assessment and knowledge of changes in forest biomass, and associated carbon gains or losses, are accurate and unbiased. Repeated measurements of individually-marked trees in permanent plots permit the estimation of rates of biomass production by tree growth and recruitment and of loss from mortality. But there are challenges, for example, simple estimates of production rate (i.e., the sum of biomass gain by growth of surviving trees and new recruits divided by census duration) decline as the census interval increases due to unrecorded growth. Even if we allow for these unobserved changes, additional biases may arise due to the non-independence of growth and mortality and to the heterogeneity and composi-tional changes within the forest. Here we examine these issues and demonstrate how problems can be minimized. We provide and compare alternative approaches to estimate net biomass production and loss from tree growth and mortality. Under the assumption that specific rates of biomass production and loss, i.e., turnover, are constant over time, we derive estimates of absolute biomass turnover rates that are independent of census duration. We show census-interval dependence of simple turnover rates grows with increasing specific turnover rates. While the time-dependent bias in simple estimates has previously been suggested to increase in proportion to the square of production, we show this relationship is approximately linear. Correlations between stem growth and mortality do not influence our estimates. We account for biomass gain by recruited stems without discounting their initial biomass in production estimates. We can reduce additional biases by accounting for differences in turnover among subpopulations (such as species, sites) and changes in their abundances. We provide worked examples from four forests covering a range of conditions (in Indonesia and Japan) and show the effects of accounting for these biases. For example, over five years in an Indonesian rain forest, simple estimates and instantaneous estimates neglecting species heterogeneity underestimated production by 4.9% and 1.6%, respectively when compared to comprehensive (instantaneous species-structured) estimates.
... Recently, many studies have examined patterns in ecosystem attributes at global scales using databases of plot-level forest inventory data (Adams and Woodward 1989;Currie 1991;Phillips et al. 1994;Cornelissen 1996;Reich and Bolstad 2001). However, there are few studies that have focused on the geographical patterns in East Asia (Ohsawa 1995;Kohyama 1999). In East Asia, the humid climate extends continuously from tropical to boreal regions without deserts at middle latitudes. ...
... Fukushima et al. (1998) reported that total LAI of TOEF, calculated by multiplying the leaf number of each species by the average leaf area within a 15-m square plot in a mature forest, was 7.59. Takahashi et al. (1999) reported that total LAI, estimated by felling all trees within a 10-m square plot in a secondary forest in TOEF, was 5.1. LAI measured with a plant canopy analyser (LAI-2000, Licor) ranged from 5-6 in peak growing periods. ...
... Tarumae in 1667 and 1739 (Sakuma 1987). Other detailed characteristics of the vegetation, soil and streams of the area have been described by Shibata et al. (1998, Takahashi et al. (1999) and Hiura (2001). ...
Shifting-gap mosaic is incorporated into the dynamic model of size-structured forests along geographic gradients. In the model named SAL(size-age-location), a forest at a geographic location has a patch-age structure, which approximates the shifting-gap mosaic, and a tree-size structure in each patch of the forest. Growth and recruitment occur in each patch and are regulated by patch-scale crowding in terms of upper basal area. Seed production depends on the basal area density of mother trees at the forest scale. Seeds are dispersed to neighboring locations of the geographic landscape. After a century-long “warming” treatment, a resident forest zone prevented, over several millennia, an invading forest zone from achieving a steady-state range of geographic distribution. Introducing the gap mosaic into the model did not make substantial changes in the response of latitudinal forest zones to the warming treatment, but only moderately accelerated the migration speed of invader species. Temporal fluctuation in seed production without interspecific synchronization, or the lottery effect, did not facilitate the migration of invader species at all.
In recent years, coarse woody debris (CWD) of deadwood has attracted attention as a long-term carbon pool for global warming problems. Environmental factors such as temperature and precipitation vary greatly with elevation. Hence, it is expected that the carbon storage by CWD varies with elevation. However, few studies have examined the abundance of CWD along elevations. Therefore, we investigated the abundance and decay classes of CWD, aboveground biomass (AGB) and aboveground net primary production (ANPP) of living trees along an elevational gradient (1600–2800 m above sea level) in subalpine coniferous forests, central Japan. AGB, ANPP and CWD decreased with increasing elevation. AGB at 2800 m was about 10% of that at 1600 m a.s.l. On the other hand, CWD at 2800 m was only 2.2% of that at 1600 m a.s.l. Thus, the ratio of CWD to AGB was lower at higher elevations. The relative frequency of small CWD increased with elevation. In addition, smaller CWD tended to decay less. The lower ratio of CWD mass to AGB at higher elevations was probably caused by smaller CWD because small CWD rapidly disappears via the high decomposition rate due to its high ratio of surface area to volume. Therefore, this study suggests that the importance of CWD relative to AGB for carbon storage decreases with elevation in subalpine forests. Climate change may alter the balance between CWD and AGB by changing ANPP and decomposition rates along elevation gradients.
Aim
Information on the amount of carbon stored in the living tissue of tree stems (sapwood) is crucial for carbon and water cycle applications. Here, we aim to investigate sapwood‐to‐stem proportions and differences therein between tree genera and derive a sapwood biomass map.
Location
Northern Hemisphere boreal and temperate forests.
Time period
2010.
Major taxa studied
Twenty‐five common tree genera.
Methods
First, we develop a theoretical framework to estimate sapwood biomass for a given stem biomass by applying relationships between sapwood cross‐sectional area (CSA) and stem CSA and between stem CSA and stem biomass. These measurements are extracted from a biomass and allometry database (BAAD), an extensive literature review and our own studies. The established allometric relationships are applied to a remote sensing‐based stem biomass product in order to derive a spatially continuous sapwood biomass map. The application of new products on the distribution of stand density and tree genera facilitates the synergy of satellite and forest inventory data.
Results
Sapwood‐to‐stem CSA relationships can be modelled with moderate to very high modelling efficiency for different genera. The total estimated sapwood biomass equals 12.87 ± 6.56 petagrams of carbon (PgC) in boreal (mean carbon density: 1.13 ± 0.58 kgC m⁻²) and 15.80 ± 9.10 PgC in temperate (2.03 ± 1.17 kgC m⁻²) forests. Spatial patterns of sapwood‐to‐stem biomass proportions are crucially driven by the distribution of genera (spanning from 20–30% in Larix to > 70% in Pinus and Betula forests).
Main conclusions
The presented sapwood biomass map will be the basis for large‐scale estimates of plant respiration and transpiration. The enormous spatial differences in sapwood biomass proportions reveal the need to consider the functionally more important sapwood instead of the entire stem biomass in global carbon and water cycle studies. Alterations in tree species distribution, induced by forest management or climate change, can strongly affect the available sapwood biomass even if stem biomass remains unchanged.
Accurate estimation of tree and forest biomass is key to evaluating forest ecosystem functions and the global carbon cycle. Allometric equations that estimate tree biomass from a set of predictors, such as stemdiameter and tree height, are commonly used.Most allometric equations are site specific, usually developed from a small number of trees harvested in a small area, and are either species specific or ignore interspecific differences in allometry. Due to lack of site-specific allometries, local equations are often applied to sites for which they were not originally developed (foreign sites), sometimes leading to large errors in biomass estimates. In this study, we developed generic allometric equations for aboveground biomass and component (stem, branch, leaf, and root) biomass using large, compiled data sets of 1203 harvested trees belonging to 102 species (60 deciduous angiosperm, 32 evergreen angiosperm, and 10 evergreen gymnosperm species) from 70 boreal, temperate, and subtropical natural forests in Japan. The best generic equations provided better biomass estimates than did local equations that were applied to foreign sites. The best generic equations included explanatory variables that represent interspecific differences in allometry in addition to stemdiameter, reducing error by 4-12% compared to the generic equations that did not include the interspecific difference. Different explanatory variables were selected for different components. For aboveground and stem biomass, the best generic equations had species-specific wood specific gravity as an explanatory variable. For branch, leaf, and root biomass, the best equations had functional types (deciduous angiosperm, evergreen angiosperm, and evergreen gymnosperm) instead of functional traits (wood specific gravity or leaf mass per area), suggesting importance of other traits in addition to these traits, such as canopy and root architecture. Inclusion of tree height in addition to stemdiameter improved the performance of the generic equation only for stembiomass and had no apparent effect on aboveground, branch, leaf, and root biomass at the site level. The development of a generic allometric equation taking account of interspecific differences is an effective approach for accurately estimating aboveground and component biomass in boreal, temperate, and subtropical natural forests.
Ecosystems are under the control of negative feedback due to resource competition, and it is difficult to explain the coexistence of many species in an ecosystem. By contrast, evolutionary history suggests that positive feedback between living organisms and environments contributes to increasing biodiversity. This paper presents a conceptual framework to interface these feedbacks, taking forests and tree communities as an example. One of the prevailing global patterns of biodiversity is the latitudinal gradient of tree species diversity in forests. A tenfold difference exists in species diversity between tropical lowland forests and either tropical high-altitude forests or temperate forests. We examined tree census data from permanent plots across various forest types in eastern Asia. Tree species diversity increased exponentially along a geographic gradient while ecosystem measures such as biomass, biomass turnover rate and asymptotic canopy height increased only linearly. Examination of a size-structure-based dynamic model of tree populations suggests that these ecosystem measures multiplicatively contribute to the extreme species diversity in tropical lowland rain forests. The same model also shows that any singular species with higher resource-use efficiency replaces all coexisting species under the constraint of functional tradeoff. Such replacement brings about increasing efficiency of ecosystems in resource exploitation, and in turn presents a greater opportunity for species coexistence. The non-linear relationship between whole ecosystem measures and species diversity develops through the process of positive feedback between the energetic efficiency of ecosystems and the functional differentiation among species, on evolutionary time scales.
I clarified aboveground biomass (AGB), net biomass increment (NBI) and its spatial heterogeneity in a cool temperate forest on a landscape scale (>2,200 ha). The relationships among AGB, NBI, and the size frequency distribution of trees of each stand were examined by combining an analysis of vegetation using aerial photographs, and data from 146 inventory plots (28.8 ha in total). This area included natural broad-leaved stands, harvested broad-leaved stands, and artificial conifer plantations. A-3/2 power distribution density function was applied to the individual mass frequency distribution of each plot. Estimated AGB in carbon (C) equivalent was 480-5,615 g C m-2 (3,130 g C m -2 on average), and NBI was -98 to 436 g C m-2 year -1 (83.0 g C m-2 year-1 on average). NBI had a single significant relationship with the reciprocal of theoretical maximum individual mass, while NBI was not significantly related to AGB. My results showed that, on a landscape scale, AGB and NBI strongly depend on the size structure of forest stands.
Quantification of annual carbon sequestration is very important in order to assess the function of forest ecosystems in combatting global climate change and the ecosystem responses to those changes. Annual cycling and budget of carbon in a forested basin was investigated to quantify the carbon sequestration of a cool-temperate deciduous forest ecosystem in the Horonai stream basin, Tomakomai Experimental Forest, northern Japan. Net ecosystem exchange, soil respiration, biomass increment, litterfall, soil-solution chemistry, and stream export were observed in the basin from 1999-2001 as a part of IGBP-TEMA project. We found that 258 g C m-2 year-1 was sequestered annually as net ecosystem exchange (NEE) in the forested basin. Discharge of carbon to the stream was 4 g C m-2 year-1 (about 2% of NEE) and consisted mainly of dissolved inorganic carbon (DIC). About 43% of net ecosystem productivity (NEP) was retained in the vegetation, while about 57% of NEP was sequestered in soil, suggesting that the movement of sequestered carbon from aboveground to belowground vegetation was an important process for net carbon accumulation in soil. The derived organic carbon from aboveground vegetation that moved to the soil mainly accumulated in the solid phase of the soil, with the result that the export of dissolved organic carbon to the stream was smaller than that of dissolved inorganic carbon. Our results indicated that the aboveground and belowground interaction of carbon fluxes was an important process for determining the rate and retention time of the carbon sequestration in a cool-temperate deciduous forest ecosystem in the southwestern part of Hokkaido, northern Japan.
To examine the characteristics of carbon exchange in coniferous forests, we analysed the seasonal and diurnal patterns of CO2 exchange, as measured using the eddy covariance method, in a Japanese cypress forest in the Kiryu Experimental Watershed (KEW) in central Japan. The net CO2 exchange data during periods of low-friction velocity conditions and during periods of missing data were interpolated. The daily CO2 uptake was observed throughout the year, with maximum values occurring in early summer. Periods of low carbon uptake were seen in late summer owing to high respiratory CO2 efflux. The diurnal and seasonal patterns of daytime CO 2 exchange at KEW were compared with those in a cool-temperate deciduous forest of the Tomakomai Experimental Forest (TOEF) in Japan. The environmental differences between evergreen and deciduous forests affected the seasonal patterns of carbon uptake. Although there were great differences in the mean monthly air temperatures between the sites, the mean monthly daytime carbon uptake was almost equal at both sites during the peak growing period. The carbon-uptake values at the same PAR level were greater before noon than after noon, especially at TOEF, suggesting the stomatal regulation of carbon uptake.
Accurate estimation of tree and forest biomass is key to evaluating forest ecosystem functions and the global carbon cycle. Allometric equations that estimate tree biomass from a set of predictors, such as stemdiameter and tree height, are commonly used.Most allometric equations are site specific, usually developed from a small number of trees harvested in a small area, and are either species specific or ignore interspecific differences in allometry. Due to lack of site-specific allometries, local equations are often applied to sites for which they were not originally developed (foreign sites), sometimes leading to large errors in biomass estimates. In this study, we developed generic allometric equations for aboveground biomass and component (stem, branch, leaf, and root) biomass using large, compiled data sets of 1203 harvested trees belonging to 102 species (60 deciduous angiosperm, 32 evergreen angiosperm, and 10 evergreen gymnosperm species) from 70 boreal, temperate, and subtropical natural forests in Japan. The best generic equations provided better biomass estimates than did local equations that were applied to foreign sites. The best generic equations included explanatory variables that represent interspecific differences in allometry in addition to stemdiameter, reducing error by 4-12% compared to the generic equations that did not include the interspecific difference. Different explanatory variables were selected for different components. For aboveground and stem biomass, the best generic equations had species-specific wood specific gravity as an explanatory variable. For branch, leaf, and root biomass, the best equations had functional types (deciduous angiosperm, evergreen angiosperm, and evergreen gymnosperm) instead of functional traits (wood specific gravity or leaf mass per area), suggesting importance of other traits in addition to these traits, such as canopy and root architecture. Inclusion of tree height in addition to stemdiameter improved the performance of the generic equation only for stembiomass and had no apparent effect on aboveground, branch, leaf, and root biomass at the site level. The development of a generic allometric equation taking account of interspecific differences is an effective approach for accurately estimating aboveground and component biomass in boreal, temperate, and subtropical natural forests.
Canopy structure and light interception were measured in an 18-m tall, closed canopy deciduous forest of sugar maple (Acer saccharum) in southwestern Wisconsin, USA, and related to leaf structural characteristics, N content, and leaf photosynthetic capacity. Light attenuation in the forest occurred primarily in the upper and middle portions of the canopy. Forest stand leaf area index (LAI) and its distribution with respect to canopy height were estimated from canopy transmittance values independently verified with a combined leaf litterfall and point-intersect method. Leaf mass, N and A
max per unit area (LMA, N/area and A
max/area, respectively) all decreased continuously by over two-fold from the upper to lower canopy, and these traits were strongly correlated with cumulative leaf area above the leaf position in the canopy. In contrast, neither N concentration nor A
max per unit mass varied significantly in relation to the vertical canopy gradient. Since leaf N concentration showed no consistent pattern with respect to canopy position, the observed vertical pattern in N/area is a direct consequence of vertical variation of LMA. N/area and LMA were strongly correlated with A
max/area among different canopy positions (r2=0.81 and r2=0.66, respectively), indicating that vertical variation in area-based photosynthetic capacity can also be attributed to variation in LMA. A model of whole-canopy photosynthesis was used to show that observed or hypothetical canopy mass distributions toward higher LMA (and hence higher N/area) in the upper portions of the canopy tended to increase integrated daily canopy photosynthesis over other LMA distribution patterns. Empirical relationships between leaf and canopy-level characteristics may help resolve problems associated with scaling gas exchange measurements made at the leaf level to the individual tree crown and forest canopy-level.
The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de Rio Negro, Venezuela. Moreover, leaf lifespan was highly correlated with a number of important leaf structural and functional characterisues. Stomatal conductance to water vapor (g) and both mass and area-based net photosynthesis decreased with increasing leaf lifespan (r2=0.74, 0.91 and 0.75, respectively). Specific leaf area (SLA) also decreased with increasing leaf lifespan (r2=0.78), while leaf toughness increased (r2=0.62). Correlations between leaf lifespan and leaf nitrogen and phosphorus concentrations were moderate on a weight basis and not significant on an area basis. On an absolute basis, changes in SLA, net photosynthesis and leaf chemistry were large as leaf lifespan varied from 1.5 to 12 months, but such changes were small as leaf lifespan increased from 1 to 5 years. Mass-based net photosynthesis (A/mass) was highly correlated with SLA (r2=0.90) and mass-based leaf nitrogen (N/mass) (r2=0.85), but area-based net photosynthesis (A/area) was not well correlated with any index of leaf structure or chemistry including N/area. Overall, these results indicate that species allocate resources towards a high photosynthetic assimilation rate for a brief time, or provide resistant physical structure that results in a lower rate of carbon assimilation over a longer time, but not both.
The tree layer consisted exclusively of Betula ermanii, whose saplings occurred commonly to recruit in the forest canopy. Betula was the climax tree. The species of the herbaceous layer were well diversified: 59 vascular species were recognized. Betula forests were found to be fairly uniform in species composition, despite being distantly located geograpically. The forest was well developed where the climate was characteristically maritime. Such a climate discourages boreal conifers such as Larix kamtchatica and Picea ajanensis from being established. Their distribution was confined to the Central Depression, where the climate is typically continental. -from English summary
The dimensional relationships (allometry) of understorey trees were contrasted with those of saplings of subcanopy-canopy trees in a humid tropical forest in Panama. The six selected species were all common, shade-tolerant trees of primary forest and were sampled in shaded understorey. The two smallest understorey species had thicker trunks and wider, heavier, leafier crowns than similar height (2.5 m tall) saplings of larger species. The former also showed greater increases in trunk diameter and crown mass per height increment, as inferred from the allometric relationships. Similar trends were observed for an Acer shrub-tree comparison in temperate forests. The above patterns are consistent with the hypothesis that understorey species have morphologies which increase light interception and persistence in the understorey, while saplings of overstorey species allocate their biomass for efficient height growth, i.e. they are adapted to efficiently pass through the understorey to reach the high-light environment of the canopy. Thus, it is important to consider dynamic as well as static functions of form in evaluating the adaptive significance of plant traits.
This paper demonstrates a new analysis of photon flux partitioning among species and an evaluation of the efficiency of photon flux capturing in terms of biomass investment. For that purpose, distributions of aboveground biomass, leaf area, and photon flux density (PPFD) were determined with the stratified harvest method in a stand of a tall herbaceous community on a floating fen at the time of peak standing crop. The stand contained 11 species and the photon flux absorbed by each species in the stand was estimated. Three tall dominant species absorbed 75% of the incident PPFD, while eight short subordinate species absorbed 2.5%. Tall species in the canopy received higher PPFD averaged over leaf area (@?"a"r"e"a). However, the PPFD absorbed per unit aboveground biomass (@?"m"a"s"s) of the tall species was not higher than that of the subordinate species. @?"m"a"s"s is a product of the leaf area ratio (LAR, the ratio of leaf area to aboveground biomass) and @?"a"r"e"a. There was a trade-off relationship between LAR and @?"a"r"e"a. To have a high @?"a"r"e"a, plants place their leaves at higher positions in the canopy, which necessarily decreases LAR. Aboveground biomass was regarded as an investment (cost) to capture PPFD (benefit). @?"m"a"s"s, as a ratio of benefit to cost, indicates an efficiency of biomass investment to capture photon flux. Tall species appeared to have an advantage over subordinate species in receiving a large fraction of incident PPFD, while subordinate species have an advantage in efficiently using their biomass to capture PPFD.
Understory vegetation undergoes successional stages during the 1st 300 yr after logging or fire disturbance in the coastal Picea-Tsuga forests of southeast Alaska. Residual shrubs and tree seedlings increase their growth within 5 yr after overstory removal. Understory biomass peaks at 5 Mg@?ha^-^1@?yr^-^1@?15-25 yr after logging. Shrubs and herbs are virtually eliminated (<0.1 Mg/ha) from the understory after forest canopies close at stand ages of 25-35 yr. Bryophytes and ferns dominate understory biomass during the following century. An understory of deciduous shrubs and herbs is reestablished after 140-160 yr. Thereafter, biomass of the shrubs, herbs, and ferns continues to increase, while bryophyte biomass and tree productivity decline. Departures from this developmental sequence are related to unusual types of stand establishment, soil, microclimate, or disturbance. The development and duration of the depauperate understory that succeeds canopy closure in southeast Alaska is closely related to the canopy structure of shade-tolerant Tsuga forests with their high foliar biomass. In young-growth forests (<100 yr), the decline in understory development immediately after canopy closure is significantly associated with tree basal area and percentage of tree canopy cover. In old-growth forests, in contrast, understory biomass is correlated with mean tree diameter, age, and volume. It is hypothesized that understory development over the chronosequence responds primarily to changes induced in the light environment by developments in the forest canopy. Maintenance of the most productive forests in the aggradation stages of development (0-100 yr) through forest management will minimize the development of a productive vascular understory and thus deprive herbivores of forage during 70-80% of the forest rotation.
Abstract Photosynthetic response to light intensity and leaf anatomy was measured in trees of 30 seral deciduous broad-leaved species native to the northern part of Japan. Early successional species showed high photosynthetic rates at high light saturation, while late successional species displayed low photosynthetic rates at high light saturation. The photosynthetic characteristics of mid-successional or gap phase species were intermediate. After reaching the maximum photosynthetic rates, the initial decline in early successional species was faster than late successional species. There was a negative correlation between the leaf stable period and saturated photosynthetic rates. Early successional species have thicker leaves with a smaller cuticle ratio (i.e., ratio of cuticle width to leaf thickness) than late successional species. There was a positive correlation between cuticle ratio and leaf longevity. The percentage of air space in leaves of early successional species was larger than that in late successional species. A positive correlation was observed between the mesophyll surface area per unit area and saturated photosynthetic rates. In gap phase species, leaf sizes and maximum photosynthetic rates were smaller in seedlings than in saplings. However, these differences between seedlings and saplings were less frequently observed than in early and late successional species. The ecological importance of leaf structure and photosynthetic characteristics is discussed in relation to forest succession.