PNNL

Abstract

Forest soil is the largest carbon pool in terrestrial ecosystem, and the soil-to-atmosphere CO2 flux (soil respiration, Rs) is the main link between soil and atmosphere. However, due to the lack of integration of field observations, substantial uncertainties exist in quantifying large-scale soil carbon effluxes, which limit our understanding of the fate of forest soil in a warming world. Here, China’s forest ecosystems were divided into six forest types in six regions, and a detailed soil respiration database (N=606) was compiled to evaluate soil carbon effluxes by conducting Monte Carlo simulations. Average annual Rs was 782.7 g C m-2 yr-1 and the soil carbon emissions totalled 1473.0 Tg C yr-1 in China’s forest ecosystems. Geographically, total soil carbon emissions in two southern regions (i.e. Southwest, Southern and Eastern China) were larger than in three northern regions (i.e. Northwest, Northern China and Northeast), accounting for about 69% and 31% of national forest soil carbon emissions, respectively. Evergreen needleleaf forest (527.1 Tg C yr-1, 52%) and evergreen broadleaf forest (337.9 Tg C yr-1, 33%) were the main source of soil carbon emissions in the two southern regions, while deciduous broadleaf forest (331.5 Tg C yr-1, 73%) was the main emissions in three northern regions. Our results provide a better understanding of the distribution and magnitude of soil carbon effluxes in China’s forest ecosystems.