Characteristics of soil carbon emissions from different forest types and regions in China

Abstract

Forest soil is the largest carbon pool in the 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 an integrated soil respiration database (N = 634) was compiled to evaluate soil carbon effluxes by random sampling with replacement. Average annual Rs was 783 g C m⁻² yr⁻¹ across China, ranking from the highest to the lowest as follows: East, Southwest, South, Northwest, Northeast and North. Total soil carbon emissions were 1472.6 Tg C yr⁻¹ (1 Tg=1 ×10¹² g) in China’s forest ecosystems, and about 69 % from three southern regions (i.e., Southwest, Southern China and Eastern China) and 31 % from three northern regions (i.e., Northwest, Northern China and Northeast). Evergreen needleleaf forest (529.09 Tg C yr⁻¹, 52 %) and evergreen broadleaf forest (343.01 Tg C yr⁻¹, 34 %) were the main sources of soil carbon emissions in three southern regions, while deciduous broadleaf forest (334.36 Tg C yr⁻¹, 74 %) was the main emissions in three northern regions. This study contributes to a comprehensive understanding of soil carbon emission characteristics among different forest types and regions in China and can provide a reference for the selection and combination of tree species in forest management to optimize the forest carbon sink potential.