title: Isometric scaling of above- and below-ground biomass at the individual and community levels in the understorey of a sub-tropical forest.
abstract: OBJECTIVE
  Empirical studies and allometric partitioning (AP) theory indicate that plant above-ground biomass (MA) scales, on average, one-to-one (isometrically) with below-ground biomass (MR) at the level of individual trees and at the level of entire forest communities. However, the ability of the AP theory to predict the biomass allocation patterns of understorey plants has not been established because most previous empirical tests have focused on canopy tree species or very large shrubs.
  
  
  METHODS
  In order to test the AP theory further, 1586 understorey sub-tropical forest plants from 30 sites in south-east China were harvested and examined. The numerical values of the scaling exponents and normalization constants (i.e. slopes and y-intercepts, respectively) of log-log linear MA vs. MR relationships were determined for all individual plants, for each site, across the entire data set, and for data sorted into a total of 19 sub-sets of forest types and successional stages. Similar comparisons of MA/MR were also made.
  
  
  RESULTS
  The data revealed that the mean MA/MR of understorey plants was 2·44 and 1·57 across all 1586 plants and for all communities, respectively, and MA scaled nearly isometrically with respect to MR, with scaling exponents of 1·01 for all individual plants and 0·99 for all communities. The scaling exponents did not differ significantly among different forest types or successional stages, but the normalization constants did, and were positively correlated with MA/MR and negatively correlated with scaling exponents across all 1586 plants.
  
  
  CONCLUSIONS
  The results support the AP theory's prediction that MA scales nearly one-to-one with MR (i.e. MA ∝ MR (≈1·0)) and that plant biomass partitioning for individual plants and at the community level share a strikingly similar pattern, at least for the understorey plants examined in this study. Furthermore, variation in environmental conditions appears to affect the numerical values of normalization constants, but not the scaling exponents of the MA vs. MR relationship. This feature of the results suggests that plant size is the primary driver of the MA vs. MR biomass allocation pattern for understorey plants in sub-tropical forests.
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China.
authors.forename: Dongliang
authors.initials: D
authors.lastname: Cheng
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China.
authors.forename: Quanlin
authors.initials: Q
authors.lastname: Zhong
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Niklas
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China.
authors.forename: Yuzhu
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China yysgeo@fjnu.edu.cn jhzhang@cuhk.edu.hk.
authors.forename: Yusheng
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute of Geography, Fujian Normal University, Fuzhou, Fujian Province 350007, China, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China, Section of Plant Biology, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA and Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou, Fujian Province 350007, China yysgeo@fjnu.edu.cn jhzhang@cuhk.edu.hk.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
mesh_terms: D018533:Biomass; D002681:China; D065928:Forests; D008027:Light; D008954:Models, Biological; D010788:Photosynthesis; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
keywords: Above-ground biomass; Cunninghamia lanceolata; Pinus massoniana; above- to below-ground ratio; allometric partitioning; allometry; below-ground biomass; broad-leafed forest; forest understorey; isometric scaling; successional stage