Age-dependent forest carbon sink: Estimation via inverse modeling

Zhou Tao;Shi Peijun;Jia Gensuo;Dai Yongjiu;Zhao Xiang;Wei Shangguan;Du Ling;Wu Hao;Luo Yiqi

 [Zhou, Tao; Shi, Peijun; Du, Ling; Wu, Hao] Beijing Normal Univ, State Key Lab Earth Surface Proc & Resource Ecol, Beijing 100875, Peoples R China.

   [Jia, Gensuo] Chinese Acad Sci, Inst Atmospher Phys, TEA, Beijing, Peoples R China.

   [Dai, Yongjiu; Wei Shangguan] Beijing Normal Univ, Coll Global Change & Earth Syst Sci, Beijing 100875, Peoples R China.

   [Zhao, Xiang] Beijing Normal Univ, State Key Lab Remote Sensing Sci, Sch Geog, Beijing 100875, Peoples R China.

   [Luo, Yiqi] Univ Oklahoma, Dept Microbiol & Plant Biol, Norman, OK 73019 USA.

ABSTRACT:  Forests have been recognized to sequester a substantial amount of carbon (C) from the atmosphere. However, considerable uncertainty remains regarding the magnitude and time course of the C sink. Revealing the intrinsic relationship between forest age and C sink is crucial for reducing uncertainties in prediction of forest C sink potential. In this study, we developed a stepwise data assimilation approach to combine a process-based Terrestrial ECOsystem Regional model, observations from multiple sources, and stochastic sampling to inversely estimate carbon cycle parameters including carbon sink at different forest ages for evergreen needle-leaved forests in China. The new approach is effective to estimate age-dependent parameter of maximal light-use efficiency (R-2=0.99) and, accordingly, can quantify a relationship between forest age and the vegetation and soil C sinks. The estimated ecosystem C sink increases rapidly with age, peaks at 0.451kgCm(-2)yr(-1) at age 22years (ranging from 0.421 to 0.465kgCm(-2)yr(-1)), and gradually decreases thereafter. The dynamic patterns of C sinks in vegetation and soil are significantly different. C sink in vegetation first increases rapidly with age and then decreases. C sink in soil, however, increases continuously with age; it acts as a C source when the age is less than 20years, after which it acts as a sink. For the evergreen needle-leaved forest, the highest C sink efficiency (i.e., C sink per unit net primary productivity) is approximately 60%, with age between 11 and 43years. Overall, the inverse estimation of carbon cycle parameters can make reasonable estimates of age-dependent C sequestration in forests.

Published in JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES.2015,120(12):2473-2492, DOI: 10.1002/2015JG002943