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Title: Significant inconsistency of vegetation carbon density in CMIP5 Earth system models against observational data: Vegetation Carbon Density in ESMs

Earth system models (ESMs) have been widely used for projecting global vegetation carbon dynamics, yet how well ESMs performed for simulating vegetation carbon density remains untested. Here we have compiled observational data of vegetation carbon density from literature and existing data sets to evaluate nine ESMs at site, biome, latitude, and global scales. Three variables—root (including fine and coarse roots), total vegetation carbon density, and the root:total vegetation carbon ratios (R/T ratios), were chosen for ESM evaluation. ESM models performed well in simulating the spatial distribution of carbon densities in root (r = 0.71) and total vegetation (r = 0.62). However, ESM models had significant biases in simulating absolute carbon densities in root and total vegetation biomass across the majority of land ecosystems, especially in tropical and arctic ecosystems. Particularly, ESMs significantly overestimated carbon density in root (183%) and total vegetation biomass (167%) in climate zones of 10°S–10°N. Substantial discrepancies between modeled and observed R/T ratios were found: the R/T ratios from ESMs were relatively constant, approximately 0.2 across all ecosystems, along latitudinal gradients, and in tropic, temperate, and arctic climatic zones, which was significantly different from the observed large variations in the R/T ratios (0.1–0.8). There were substantial inconsistenciesmore » between ESM-derived carbon density in root and total vegetation biomass and the R/T ratio at multiple scales, indicating urgent needs for model improvements on carbon allocation algorithms and more intensive field campaigns targeting carbon density in all key vegetation components.« less
Authors:
 [1] ; ORCiD logo [2] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [2] ;  [4] ; ORCiD logo [5]
  1. San Diego State Univ., San Diego, CA (United States). Biology Dept.; Univ. of Texas, El Paso, TX (United States). Biology Dept.
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division and Climate Change Science Inst.
  3. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of Geographic Sciences and Natural Resources Research
  4. San Diego State Univ., San Diego, CA (United States). Biology Dept.
  5. San Diego State Univ., San Diego, CA (United States). Biology Dept.; Univ. of Texas, El Paso, TX (United States). Biology Dept.; Chinese Academy of Sciences (CAS), Beijing (China). Northeast Inst. of Geography and Agroecology
Publication Date:
Grant/Contract Number:
AC05-00OR22725; ACI-1053575
Type:
Published Article
Journal Name:
Journal of Geophysical Research. Biogeosciences
Additional Journal Information:
Journal Volume: 122; Journal ID: ISSN 2169-8953
Publisher:
American Geophysical Union
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; carbon density; root; vegetation; root/vegetation ratio; Earth system models
OSTI Identifier:
1389091
Alternate Identifier(s):
OSTI ID: 1389092; OSTI ID: 1393808