Diagnosing Linearity Along the Carbon Cascade in Terrestrial Biosphere Models and Observations

作者：H. Zhang, Vivek K. Arora, Peter Anthoni, Thomas A. M. Pugh, Atul K. Jain, Wenping Yuan, Yadvinder Malhi, Julia E. M. S. Nabel, Daniel S. Goll, Julia Pongratz, Benjamin Poulter, Anthony P. Walker, Sönke Zaehle, Jürgen Knauer, Etsushi Kato, Ruijie Ding, Minxue Tang, Stephen Sitch, Michael O’Sullivan, César Terrer, Hanqin Tian, Naiqing Pan, Pierre Friedlingstein, Akihiko Ito, Qing Sun, Jeanne Decayeux, Benjamin D. Stocker · 发表于：Global Change Biology · 年份：2026 · DOI：10.1111/gcb.70982 · 研究领域：Plant Water Relations and Carbon Dynamics、Plant responses to elevated CO2、Atmospheric and Environmental Gas Dynamics

ABSTRACT Elevated carbon dioxide (eCO 2 ) acts as a fertiliser for photosynthesis, driving an increase in gross primary production (GPP). However, it is unclear how effectively increased GPP propagates along the ‘carbon (C) cascade’ to increase net primary production (NPP) and vegetation C stocks ( C veg ) in different plant compartments. Vegetation models were criticised for being overly sensitive to photosynthesis (source‐driven), neglecting sink‐driven processes which may attenuate (or amplify) changes in NPP and vegetation C stocks. Here, we introduce an analytical framework to diagnose linearity ( L ) as ratios of relative changes in linked fluxes and pools. We then apply this framework to 16 models of the TRENDY v11 ensemble and to observation‐based estimates of CO 2 sensitivities. We found widely varying global patterns in L across models. Six models showed a majority of grid cells with larger relative changes in NPP than in GPP ( L NPP:GPP > 1 for > 60% of gridcells), indicating increased vegetation carbon use efficiency under eCO 2 . Only three models had L NPP:GPP < 1 for > 60% of gridcells. Four models showed a majority of gridcells with larger relative changes in estimated steady‐state C veg than in NPP, while five models showed the opposite—in both cases with a large spread of L Cveg*:NPP across grid cells within models. Observations‐based analysis reveals median L Cveg*:NPP < 1 overall but evidence is insufficient for a conclusion. Three models sh...