PRECIPITATION AND UNDERSTORY VEGETATION DIVERSITY DRIVE VARIATIONS IN SOIL ORGANIC CARBON DENSITY: RESULTS FROM FIELD SURVEYS AND SATELLITE DATA OF TWO DIFFERENT PERIODS IN THE GREATER KHINGAN MOUNTAINS OF NORTHEAST CHINA

The forest ecosystem in Greater Khingan Mountains (GKM) is the largest primary forest in northern China Accurate assessment of the regional carbon (C) pool of soils and analysis of the control factors are essential for setting appropriate forest management policies. Our study was designed to prove the hypothesis that forest soil acts as a C sink owing to continuous C accumulation, which results from constant biomass production within the GKM forests. We investigated topsoil (0-20 cm) C dynamics and diving force in GKM forests (both the Inner Mongolia and Heilongjiang sectors) based on field data from 2000 to 2019. The mean soil organic C density (SOCD) in the topsoil was 10.64 +/- 0.83 kg C m(-2) across the GKM, and the increase rate was 0.15 +/- 0.05 kg C m(-2) y(-1). Our results also demonstrated the critical role of precipitation and under vegetation diversity in shaping soil organic C dynamics across the GKM, suggesting that the relationship between the soil C cycle and temperature is unstable in northern ecosystems. Our results provided a new reference range for estimating surface soil C pools in GKM forests ecosystems based on field measurements.