Measurement of soil properties
We determined several soil physical and chemical properties in August 2020 by collecting soil samples from the 0-10 cm layer. We selected six points in each plot near the other sampling points and collected soil at each point from 0-10 cm using a soil auger (3 cm diameter). At each point, we collected two soil samples, combined them, and passed soil through a 2 mm sieve for determining the physical and chemical properties of the soil in the laboratory.
For each soil sample, we determined total carbon and total nitrogen content in the soil using an elemental analyzer (Elementar Vario MACRO CUBE); total phosphorus content using an ultraviolet spectrophotometer (UV-1800, Mapada, Shanghai, China) with the sodium hydroxide fusion method; organic carbon content using the potassium dichromate external heating method; nitrate (NO3--N) and ammonium (NH4+-N) by extraction using KCl (2 mol·L-1) with a flow analyzer; available phosphorus content using the sodium bicarbonate molybdenum antimony anti-colorimetric method; and microbial biomass carbon and microbial biomass nitrogen using the chloroform fumigation extraction method.