Long-term effects of management history on carbon dynamics in agricultural soils in Northwest China

Human activities and climate change have substantial effects on soil ecosystems. The historical variations in soil organic carbon (SOC) in Northwest China were investigated in this paper. Using an agro-ecosystems database, a process-based model, Denitrification-Decomposition (DNDC), was used to support a regional SOC simulation. Over the 1980s and 1990s, the SOC storage (0-50 cm) reduced slightly from 1.25 PgC (pentagrams of carbon, 1 PgC = 10(15) gC) and stabilized at 1.23 PgC. SOC significantly differed in Northwest China farmland both temporally and spatially. Climatic variability magnified the response of the spatially heterogeneous region to climate and greatly influenced the vegetation and soil. The SOC increase appeared in areas with a mild and humid climate in the east, including Shaanxi, Gansu, Ningxia and south Xinjiang. Management practices greatly affect SOC dynamics through straw C input, increased 46.31 % C budget and 20.52 % total SOC (TSOC) through 60 % crop residue incorporation. Reducing human disturbance to the surface soil through conservative tillage and improving soil fertility through reasonable nutrient input and water-use efficiency have important implications for C sequestration, emission reduction and soil productivity improvement in arid or semiarid agricultural farmland regions.