Stand Leaf Biomass Research Articles

Mathematical consideration of the age-related decline in leaf biomass in forest stands under the self-thinning law

In addition to the hypothetical trends proposed by Kira and Shidei (1967), Odum (1969) and Ryan et al. (1997, 2004), Oshima et al. (1958) observed a complicated age-related change in stand leaf biomass in Abies forests. To explain this change in stand leaf biomass theoretically, the age-related change in leaf biomass was modeled based on the following three assumptions after canopy closure: (i) the self-thinning law; (ii) expanded allometric scaling between the mean individual leaf mass and mean individual total mass; and (iii) the formulation of a logistic function for stand density change. The model successfully explained these three trends in forest stand leaf biomass and introduced expanded allometric scaling including the properties of the model based on simple allometric scaling proposed by Ogawa (2017). Therefore, the model developed here can generalize age-related changes in forest stand biomass better than the model proposed by Ogawa (2017).

Modeling age-related leaf biomass changes in forest stands under the assumptions of the self-thinning law

Key message The present model indicates that possibility of leaf biomass constancy in forest stands is not so high, and that forest stand leaf biomass declines after canopy closure.

Self-thinning of stems, branches, and leaves in overcrowded mangrove Kandelia obovata stands on Okinawa Island, Japan

The self-thinning exponent of stems, branches and leaves of the subtropical mangrove Kandelia obovata stands was investigated over seven years. According to Weller's allometric model, the slope of the self-thinning exponent αx of a partial organ “x” is calculated from the allometric constants θx and δx obtained from the allometric relationships between mean tree height H¯ (m) and organ mass density d¯ (kgm−3) with mean organ mass w¯x (kg). The self-thinning exponent, αx, was estimated to be 1.509 for stem, 1.647 for branch, 1.090 for leaf, and 1.507 for aboveground. The ϕx-value which is the allometric coefficient between s¯ (mean occupied area per tree) and w¯x (kg) was 0.6629±0.0250 for stem, 0.6072±0.0229 for branch, 0.9167±0.0356 for leaf, and 0.6637±0.0297 for aboveground. The value did not significantly differ from 2/3 but did significantly differ from 3/4 for stem, branch, and aboveground, indicating that the self-thinning exponents for woody parts did not significantly differ from 3/2. Our result suggests that the self-thinning exponent is closer to 3/2 than to 4/3. In contrast, the ϕL-value for leaf significantly differed from both 2/3 and 3/4 but did not significantly differ from 1.0, indicating that stand leaf biomass was constant regardless of population density. The self-thinning exponent for leaf had a negligible effect on that for aboveground mass due to the combined mass of all woody organs. Our data support the 3/2 power law for aboveground self-thinning. For overcrowded K. obovata stands, self-thinning could be explained by a simple geometric model rather than a metabolic model.

Self-thinning exponents for partial organs in overcrowded mangrove Bruguiera gymnorrhiza stands on Okinawa Island, Japan

According to the Weller’s allometric model, the slope of the self-thinning exponent αx of a partial organ was calculated from the allometric constants θx and δx obtained from the allometric relationships of mean tree height H¯(∝w¯xθx) and of organ mass density d¯(∝w¯xδx) to mean organ mass w¯x. The self-thinning exponent, αx(=1/{1−(δx+θx)}), was estimated to be 1.519 for stem, 1.515 for branch, 1.095 for leaf, and 1.482 for aboveground. The αx-value obtained from the estimates θx and δx cannot be used for its significance test because these two estimators are dependent of each other. The allometric relationship of the mean occupied area per tree s¯(=1/ρ∝w¯xϕx) to w¯x gives the self-thinning exponent αxk, calculated as 1/ϕx, which is mathematically and statistically (by ordinary least squares) equivalent to 1/{1−(δx+θx)}. The ϕx-value was 0.6582 for stem, 0.6601 for branch, 0.9129 for leaf, and 0.6748 for aboveground mass. The ϕx-value was not significantly different from 2/3, but it was significantly different from 3/4 for stem, branch, and aboveground. This means that self-thinning exponents for woody parts were not significantly different from 3/2. This result suggests that the self-thinning exponent was close to 3/2 rather than 4/3. On the other hand, the ϕL -value for leaf was significantly different from both 2/3 and 3/4, but it was not significantly different from 1.0. This means that stand leaf biomass was constant regardless of population density. The self-thinning exponent for leaf had a negligible effect on that for aboveground because of the small amount of leaf mass compared with the combined mass of the woody organs. Therefore, the present results based on the allometric model of partial organs roughly support the 3/2 power law for aboveground self-thinning. For overcrowded Bruguiera gymnorrhiza stands, self-thinning could be explained by a simple geometric model rather than a metabolic model.

Stem, branch and leaf biomass‐density relationships in forest communities

AbstractDefining and quantifying biomass–density relationships in dense plant stands has been a long‐standing issue in both theoretical and empirical studies. Most existing/traditional studies focus on whole plant individuals, without considering different plant components (e.g., stem, branch and leaf). However, the analysis of biomass–density relationships for different plant parts is linked to those for whole plants, and thus important for understanding plant strategies for utilizing resources and community dynamics. In our study, we investigated standing stem (MS), branch (MB) and leaf (ML) biomass–density relationships, across a range of forest communities in China. The results showed that there was no constant predicted value (e.g., −1/2 or −1/3 for MS; −1/2, −1/3 or 0 for MB and ML) that can describe all the relationships, and that the scaling exponents for stem, branch and leaf biomass varied across different forest types. In particular, standing leaf biomass (leaf biomass per unit area) was not constant in these forest communities. Furthermore, stem biomass–density lines were steeper than corresponding branch and leaf lines across most of these forest communities.

Mathematical analysis of age-related changes in leaf biomass in forest stands

Temporal changes in leaf biomass during forest stand development were theoretically analyzed on the basis of two mathematical models, both of which assume that changes in stand density with age follow a logistic equation. According to the pipe model theory, stem cross-sectional area at the crown base was used to determine the time course of leaf biomass change. In Model I, the growth curve of average leaf mass of a tree is expressed by a single logistic equation, with the result that stand leaf biomass shows a singular peak maximum of leaf biomass, coinciding with crown closure. Model I results correspond to the hypothetical trend proposed by Ryan et al. (1997. Adv. Ecol. Res. 27: 213–262). In Model II, the growth curve of average leaf mass of a tree is expressed by several logistic equations, representing a growth phase shift, with the result that the time trend of stand leaf biomass shows a more or less constant level after the intial peak maximum. Stand leaf biomass constancy is supported by the mathem...

Self-thinning of leaf, wood and aboveground in overcrowded mangrove Bruguiera gymnorrhiza stands in Okinawa Island, Japan

The allometric relationships of mean tree height to mean organ mass w were studied in Bruguiera gymnorrhiza stands. According to Weller's allometric model, the self-thinning exponent α was estimated to be 1.11 in leaf, 1.55 in wood and 1.47 in aboveground. The self-thinning exponent α in leaf was not significantly different from 1.0, which showed that the stand leaf biomass was constant regardless of the population density ρ. The α was not significantly different from 3/2 in wood and aboveground, which concluded that the 3/2 power law of self-thinning holds in overcrowded B. gymnorrhiza stands.

Relationships among the Stem, Aboveground and Total Biomass across Chinese Forests

Abstract Forest biomass plays a key role in the global carbon cycle. In the present study, a general allometric model was derived to predict the relationships among the stem biomass MS, aboveground biomass MA and total biomass MT, based on previously developed scaling relationships for leaf, stem and root standing biomass. The model predicted complex scaling exponents for MT and/or MA with respect to MS. Because annual biomass accumulation in the stem, root and branch far exceeded the annual increase in standing leaf biomass, we can predict that MT∝MA∝MS as a simple result of the model. Although slight variations existed in different phyletic affiliations (i.e. conifers versus angiosperms), empirical results using Model Type II (reduced major axis) regression supported the model's predictions. The predictive formulas among stem, aboveground and total biomass were obtained using Model Type I (ordinary least squares) regression to estimate forest biomass. Given the low mean percentage prediction errors for aboveground (and total biomass) based on the stem biomass, the results provided a reasonable method to estimate the biomass of forests at the individual level, which was insensitive to the variation in local environmental conditions (e.g. precipitation, temperature, etc.).

Altitudinal Change in LAI and Stand Leaf Biomass in Tropical Montane Forests: a Transect Study in Ecuador and a Pan-Tropical Meta-Analysis

Leaf area index (LAI) is a key parameter controlling plant productivity and biogeochemical fluxes between vegetation and the atmosphere. Tropical forests are thought to have comparably high LAIs; however, precise data are scarce and environmental controls of leaf area in tropical forests are not understood. We studied LAI and stand leaf biomass by optical and leaf mass-related approaches in five tropical montane forests along an elevational transect (1,050–3,060 m a.s.l.) in South Ecuador, and conducted a meta-analysis of LAI and leaf biomass data from tropical montane forests around the globe. Study aims were (1) to assess the applicability of indirect and direct approaches of LAI determination in tropical montane forests, (2) to analyze elevation effects on leaf area, leaf mass, SLA, and leaf lifespan, and (3) to assess the possible consequences of leaf area change with elevation for montane forest productivity. Indirect optical methods of LAI determination appeared to be less reliable in the complex canopies than direct leaf mass-related approaches based on litter trapping and a thorough analysis of leaf lifespan. LAI decreased by 40–60% between 1,000 and 3,000 m in the Ecuador transect and also in the pan-tropical data set. This decrease indicates that canopy carbon gain, that is, carbon source strength, decreases with elevation in tropical montane forests. Average SLA decreased from 88 to 61 cm2 g−1 whereas leaf lifespan increased from 16 to 25 mo between 1,050 and 3,060 m in the Ecuador transect. In contrast, stand leaf biomass was much less influenced by elevation. We conclude that elevation has a large influence not only on the leaf traits of trees but also on the LAI of tropical montane forests with soil N (nitrogen) supply presumably being the main controlling factor.

An annual cycle of biomass and productivity of Vallisneria americana in a subtropical spring-fed estuary

An annual cycle of biomass and productivity of wild celery ( Vallisneria americana) was studied in Kings Bay, FL, USA. In situ growth rates were measured monthly between March 2001 and June 2002 in high-density stands, using a modified hole-punching technique, and applied to shoot density data to obtain areal estimates of production. Mean shoot density varied greatly over the study period, ranging between 200 and 800 shoots m −2. Mean total biomass ranged between 162 and 1013 g m −2, with aboveground material comprising, on average, 70% of total biomass. Total annual estimated production of new attached shoots was 519 g m −2. Leaf growth rates peaked at >50 mg shoot −1 d −1, and mass-specific leaf growth ranged 0.6–1.8% d −1. Annually, individual shoots produced 7.4 g of leaf material and completely replaced standing leaf biomass 3.5 times. Areal leaf production was highest in late spring/summer of 2001, and ranged between 3.6 and 23.0 g m −2 d −1. Annual total leaf production was 2704 g m −2. Seasonality was not apparent in most variables monitored monthly; only 1 of the 64 relationships we examined between environmental variables (nutrients, chlorophyll a, and irradiance) and Vallisneria biological variables were significant, with relative growth rate increasing linearly with irradiance. Peak biomass and productivity of Vallisneria in Kings Bay were high compared to literature values for other Vallisneria populations as well as global averages for well-studied seagrasses, emphasizing the potential importance of Vallisneria to whole ecosystem functioning in springs, lakes, and oligohaline reaches of many estuaries.

Foliage loss due to snow, wind, and winter drying damage: its effects on leaf biomass of some western conifer forests

Damage to forest canopies by wind, snow, or winter desiccation significantly reduced stand leaf biomass and area below "steady-state" levels in several western coniferous forests. Leaf biomass of 12 different western conifer forests sampled for an average of 4 years was reduced by as much as 36.3, 34.5, and 42.2% by single wind damage, snow breakage, or winter desiccation events, respectively, during the sampling interval. Foliage loss exceeded annual foliage production as estimated from leaf litterfall in about half the stands where damage occurred. Production efficiency (Mg dry matter•ha−1•year−1•Mg−1 foliage) by remaining foliage appeared to increase after damage. Based on the data available, major canopy damage appears to occur at roughly 9- to 16-year intervals in western coniferous forests. However, this canopy damage is epidosic and unpredictable. Such damage adds an additional measure of uncertainty to forest productivity models.

Theoretical limits of belowground production by Spartina alterniflora: An analysis through modelling

Emperical measurements of standing leaf biomass in tall-form stands of Spartina alterniflora and climatic data were used to solve a growth model in order to place upper limits on belowground production. The model was solved using data from Great Sippewissett Marsh in Massachusetts, Flax Pond in New York, and a Sapelo Island marsh in Georgia. The upper limits of belowgroung production were calculated for these marshes, 1.1, 3.2, and 6.5 kg C m −2 yr −1, respectively, when a zero rate of belowground respiration was assumed. Best estimates of net belowground production were calculated, 0.6, 0.6, and 1.4 kg C m −2 yr −1, respectively, when the respiration of roots and rhizomes was subtracted from the gross rate of belowground production and when we assumed that the loss of belowground biomass from death or exudation of organics was great enough to maintain the average annual belowground biomass in steady state. Best estimates of belowground production gave predicted CO 2 exchange rates that were consistent with all of the independent measurements of gas exchange, but suggested that CO 2 from sources belowground, probably from respiration, may be lost through the leaves. Photosynthetic efficiencies predicted by the model were similar to those reported for a number of other highly productive species.