Understory Vegetation and Drought Effects on Soil Aggregate Stability and Aggregate‐Associated Carbon on the Loess Plateau in China

Core Ideas Precipitation–throughfall exclusion and the removal of understory had no influence on total SOC. Throughfall exclusion and removal of the understory significantly affected soil aggregate stability. Throughfall exclusion and lack of understory also affected aggregate‐associated organic C pools. Restoration of understory vegetation had some potential to increase total SOC sequestration. Artificial afforestation is a common strategy for ecological recovery on the Loess Plateau, China, which causes the development of understory vegetation and drought stress. However, the influence of the understory vegetation and drought conditions on soil aggregate stability and aggregate‐associated soil organic carbon (SOC) are still not well understood. We evaluated the impacts of understory development and drought stress on soil aggregate stability and associated SOC during 2015 and 2016 in an artificial afforestation area in Shaanxi Province, China. The study had four treatments: control (CK), precipitation and throughfall excluded + understory present (TE), precipitation and throughfall allowed + understory removed (NU), and precipitation and throughfall excluded + understory removed (TE‐NU). Soil moisture was significantly reduced by the exclusion of precipitation and throughfall. Aboveground biomass in the CK was significantly higher than that of TE. Precipitation–throughfall exclusion and the removal of understory vegetation significantly decreased soil aggregate stability and aggregate‐associated organic C pools, while they had no influence on the total SOC pools. This indicated that soil aggregate stability and aggregate‐associated organic C may be more sensitive to changes in the external environment. These suggest that understory vegetation restoration had some potential to increase total SOC sequestration in the artificial afforestation on the Loess Plateau of China.