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1

Nitrogen content and biomass: scaling from the tree to the forest level

100%

Cheng D.-L. , Zhong Q.-L.

Polish Journal of Ecology

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2012

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tom 60

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nr 4

EN

Nitrogen is an essential nutrient for plant growth. Although much has been learned about its utilization and distribution within the plant body, little is known about the relationship between nitrogen content and standing biomass at the level of entire forests. Data for nitrogen content (N) and biomass (M) of 10 deciduous species in USA at the individual trees level and 37 species grown in three forest biomes (i.e. tropic, subtropics, and temperate) in China at stands level were gathered to determine the N versus M scaling relationships for different tissue- and organ-types (e.g. bark and leaves). Model Type II regression protocols were used to calculate scaling exponents and allometric constants (i.e. slopes and y-intercepts of log-log bivariate plots, respectively) between N and M to. At the level of individual plants, N scaled nearly isometrically with M for the different tissue- and organ-types (i.e. Nα M 0.97–1.04). At the stand-level, N scaled similarly with respect to leaf, branch, and bark M, despite differences in stand size-frequency distributions and species composition. However, total stand N scaled allometrically with respect to total stem or root M and thus to total stand mass (i.e. N α MT 0.77–0.87). This was attributed to the accumulation of wood (and other ‘necromass’ tissue components that have lower N content than physiologically active tissues) in progressively older (and thus more massive) tree stands. When coupled to the scaling of N with respect to annual plant growth rates, these exponents provide important boundary conditions with which to model forest nutrient cycling.

2

Nitrogen content and biomass : scaling from the tree to the forest level

100%

Cheng D.-L. , Zhong Q.-L.

Polish Journal of Ecology

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2012

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tom Vol. 60, nr 4

699--706

EN

Nitrogen is an essential nutrient for plant growth. Although much has been learned about its utilization and distribution within the plant body, little is known about the relationship between nitrogen content and standing biomass at the level of entire forests. Data for nitrogen content (N) and biomass (M) of 10 deciduous species in USA at the individual trees level and 37 species grown in three forest biomes (i.e. tropic, subtropics, and temperate) in China at stands level were gathered to determine the N versus M scaling relationships for different tissue- and organ-types (e.g. bark and leaves). Model Type II regression protocols were used to calculate scaling exponents and allometric constants (i.e. slopes and y-intercepts of log-log bivariate plots, respectively) between N and M to. At the level of individual plants, N scaled nearly isometrically with M for the different tissue- and organ-types (i.e. N [proportionality] M [0.97–1.04]). At the stand-level, N scaled similarly with respect to leaf, branch, and bark M, despite differences in stand size-frequency distributions and species composition. However, total stand N scaled allometrically with respect to total stem or root M and thus to total stand mass (i.e. N [proportionality] M[T] [0.77–0.87]). This was attributed to the accumulation of wood (and other ‘necromass’ tissue components that have lower N content than physiologically active tissues) in progressively older (and thus more massive) tree stands. When coupled to the scaling of N with respect to annual plant growth rates, these exponents provide important boundary conditions with which to model forest nutrient cycling.

3

Age-related relationship between annual productivity and body size of trees: testing the metabolic theory

80%

Cheng D. L. , Wang G.-X. , Zhong Q.-L.

Polish Journal of Ecology

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2009

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tom 57

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nr 3

441-449

EN

Metabolic theory of ecology predicts a 3/4 power relationship between annual productivity PT and body size MT (i.e., P ∞ M3/4), which has important implications to estimates of carbon fluxes, ecosystem health, global carbon budgets, and a variety of other phenomena. To test this prediction, we examined a large dataset for Chinese forests. Such dataset covers six major forest biomes and a total of 17 forest types grown across a range of annual temperature (–6.6 to 25.2ºC), mean annual rainfall (27 to 2989 mm), elevation (10 to 4240 m a.s.l.), and stand age (3 to 350 yrs.). Reduced major axis (RMA) regression analyses were used to compare the PT versus MT scaling exponents and normalization constants (i.e., slopes and Y-intercepts of log-log linear relationships, respectively). Comparisons were made for ten different age-sequences (stand age ranges from 20 to 200 yrs). When stand age was less than 100 yrs, relationship of PT versus MT had similar scaling exponents (αRMA » 1.0), while the Y-intercepts decreased systematically. When stand age exceeded 140 yrs, scaling exponents decreased (αRMA <0.86). Both the aboveground annual productivity and aboveground body size per individual tree (PA and MA, respectively) showed the same behavior. We therefore conclude that the relationship of PT versus MT systematically declined with the stand age, and was inconsistent with the predictions of metabolic theory

4

Invariant allometric relationship between above- and below-ground biomass along a moisture gradient in North - West China

70%

Cheng D. L. , Wang G.-X. , Tang Q.-L. , Li T. , Zhong Q.-L.

Polish Journal of Ecology

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2009

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tom 57

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nr 4

669-675

EN

Biomass allocation pattern is an important plant characteristic which influences how plants respond to abiotic and biotic heterogeneity. Prior studies indicate that above-ground biomass scales nearly isometrically with respect to below-ground biomass regardless of environment or phyletic affinity. However, such rule has been mostly tested with data on trees and usually without drought stress. Given the importance of this predicted relationship, it should be evaluated for a wider range of species and environmental conditions. Variations of the above- and belowground biomass (MA and MR, respectively) were determined from five sites in north-west China, which compose a natural moisture gradient (aridity index ranging from 0.95 to 1.98). Model Type II regression protocols were used to compare the numerical values of MA vs MR scaling exponents (i.e. slopes of log-log linear relationships). The resulting five scaling exponents were indistinguishable and had a similar, nearly isometric slope (i.e. MA ∞ MR ͌ ¹‧⁰). Significant variation was observed in the Y-intercepts of the five regression curves, because of the absolute differences in MA or MR. These results support prior allometric theory, which reveals an isometric relationship between above- and below-ground biomass, and may provide a suitable method to estimate the regional below-ground biomass based on the direct aboveground measurements.

5

Isometric scaling relationship between leaf number and size within current-year shoots of woody species across contrasting habitats

70%

Li T. , Deng J.-M. , Wang G.-X. , Cheng D.-L. , YU Z.-L.

Polish Journal of Ecology

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2009

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tom 57

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nr 4

659-667

EN

The scaling relationship between the number and size of plant’s components has been observed traditionally as reflective of a trade-off in resource allocation over ontogeny. The recent finding of a negative isometric leaf size/number trade-off across 24 deciduous woody species extends knowledge of such trade-offs to current-year shoots. Before generally accepted, this isometry has to be consistent across more datasets that represent diverse habitats. We tested this scaling relationship using 12 deciduous shrub species from the western Gobi Desert and 56 woody species from the northeastern temperate zone of China. Our results showed that leaf number per stem mass of current-year shoots scaled approximately isometrically with individual leaf mass within and across habitats, which, combined with the independence of total leaf mass and individual leaf mass, supports isometric scaling for shoot-scale leaf deployment. However, the intercepts of these relationships decreased significantly along the environmental gradients, suggesting that habitats could place a constraint on the total leaf number that can be supported by a given size shoot. Convergence towards higher leaf number and smaller leaf size for some desert species suggests important adaptive implications for photosynthetic carbon gain and reproductive growth.