2.3 ampling procedure
Vegetation sampling was performed in two random quadrats (0.5 × 0.5 m) in each experimental plot in mid-August 2019 and 2020. Plant species in each quadrat were identified and destructively clipped to measure shoot biomass. In 2019 and 2020, the quadrats were conducted at different sites in each plot to avoid resampling. Plant samples were weighed and recorded after over-drying at 65°C for 48 h. The plant diversity (Shannon index, H ′) was measured for each plot (Yu et al., 2021).
Soil samples were botained randomly in the end of growing season (mid-August in 2019 and 2020). Three holes (soil depth: 10 cm) were drilled from each plot, and the soil from these holes was mixed into one soil sample per plot (~200 g). Each mixed soil sample was sieved via a soil mesh (2 mm bore diameter) to take out plant roots and stones. Soil and plant root samples was stored in the laboratory.