7种木本植物的分支指数与代谢指数

West、Brown和Enquist提出的植物分形网络模型(简称WBE模型)认为: 植物的分支指数(1/a, 1/b)决定植物的代谢指数, 当分支指数1/a、1/b分别为理论值2.0、3.0时, 代谢速率与个体大小的3/4次幂成正比, 但是恒定的3/4代谢指数并不能全面地反映植物的代谢情况。基于分支指数的协同变化, Price、Enquist和Savage对WBE模型进行扩展, 提出植物分支参数协同变化模型(简称PES模型)。该文借助于PES模型分析了7种木本植物的分支指数和代谢指数。结果表明: 物种间叶面积与叶生物量呈异速生长关系, 基于叶面积得到的分支指数1/a和代谢指数θ在物种间无显著差异, 基于叶生物量得到的分支指数1/a、1/b和代谢指数θ在物种间均存在显著差异, 但基于叶面积和叶生物量分别拟合出的整体分支指数1/a、1/b和代谢指数θ与理论值均无显著差异, 且用叶面积作为代谢速率的替代指标比用叶生物量分析得出的代谢指数与理论值更接近。今后研究应当关注植物叶面积与叶生物量的异速生长关系对植物代谢速率及相关功能特性的影响。

Branching and metabolic exponents in seven woody plants

Aims The fractal-like network model of plants (the WBE model) considers that the branching exponents 1/a and 1/b determine the metabolic exponent θ in plants. However, the constant 3/4 metabolic exponent does not completely reflect the plant metabolic scaling. Price, Enquist and Savage extended the WBE model by assuming that branching exponents are not constant but covary with each other, and developed the branching traits covariation model of plants (the PES model). In this paper, we study and compare branching exponents and metabolic exponents in seven woody plants based on leaf area and leaf biomass by using the PES model.Methods To test the PES model, data on leaf area and leaf biomass of seven woody species were used to determine the values of branching and metabolic exponents. Standardized major axis (SMA) regression protocols were used to determine the numerical values of scaling exponents and normalization constants for each species and across the seven species using the software SMATR. Furthermore, test of a common slope across all species and comparisons between the estimated values and theoretical values proposed by the WBE model were also performed by using the SMATR. Specifically, if the value of p exceeds a critical level, then it is considered that there would be no significant differences among the groups compared and that a common slope can be determined; if the value of p is below the critical level, then it would indicate that the estimated value would be significantly different from the theoretical value. Important findings Significant allometric relationships between leaf area and leaf biomass were verified within and across species. Specifically, leaf area scaled as 0.86-power of leaf biomass across the entire data sets. Therefore, values of branching and metabolic exponents were determined by using leaf biomass and leaf area separately. Values of the branching exponent 1/a and the metabolic exponent θ based on leaf area were statistically indistinguishable among the seven woody species. On the contrary, values of the branching exponents 1/a and 1/b and the metabolic exponent θ based on leaf biomass differed significantly among the seven woody species. Values of the branching exponents and the metabolic exponent estimated from both leaf area and leaf biomass across the entire data set were all statistically indistinguishable from the theoretical values. Furthermore, compared with the value of metabolic exponent based on leaf biomass, the value of metabolic exponent based on leaf area was statistically more comparable to the theoretical value. The effect of allometric relationship between leaf area and leaf biomass on metabolic rate and relative functional traits of plants should be paid more attention in future research.