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.