Root derived C rather than root biomass contributes to the soil organic carbon sequestration in grassland soils with different fencing years

Belowground carbon (C) input is a key component of the global C cycle. However, how does fencing affect Belowground net primary production (BNPP) and the contribution of root derived C to belowground C input remains poorly studied. In this study, the in-growth soil cores-13C method was used to quantify net root C input. Five different plant communities of different fencing years (1 year, 5 years, 10 years, 25 years, 30 years) in the Loess Plateau of China, characterized by herbs and shrubs were investigated. BNPP was increased with the increase of fencing years: 61.54~140.23 gC·m− 2·yr− 1. Root derived C in soil represented a considerable contribution to BNPP varying from 57 to 81 %, and the proportion of root derived C to BNPP was decreased with the fencing years. The contribution of root derived C to soil organic carbon (SOC) was 3 %~5 % during one-year growth. Our results underline the fact that fencing is an effective means to improve the BNPP and plant community. Root derived C rather than root biomass contributes to the SOC sequestration in grassland soils with different fencing years. Fencing increases the contribution of root derived C to SOC mainly by increasing root C content.