2.3.3 Soil properties
Soil was also sampled from soil cores along the vertical soil profile
(see section 2.3.1). Soil samples from each layer were divided into two
subsamples. Fresh subsamples were immediately weighed and oven-dried at
105 °C to determine the soil water content (SWC, g
g-1). The remaining soil subsamples were air-dried and
passed through a 100-mesh (0.15 mm) sieve to determine soil
physicochemical properties. Soil
total carbon (TC) and total nitrogen (TN) levels were determined by
combustion in an elemental analyzer (Vario
MAX; Elementar, Germany), and
total phosphorus (TP) was measured using the sulfuric acid-soluble
perchlorate acid-molybdenum antimony colorimetric method (Hu et al.,
2016). Dissolved organic carbon was extracted with deionized water (1:5
w/v soil to water) and determined using an elemental analyzer (Vario
Macro Analyzer; Elementar, Germany). Ammonium nitrogen
(NH4+-N) and nitrate nitrogen
(NO3--N) were
extracted in the 2 mol
L-1 KCl solution, and the supernatant was measured
using a flow analyzer (SEAL Analytical, Germany). Available phosphorus
(aP) was extracted with 0.5 mol L-1NaHCO3 at pH 8.5, and then determined by molybdenum
antimony anti-colorimetry. Soil pH was determined in a 1:2.5 (w/v)
soil-water suspension (SevenEasyS20; Mettler Toledo, USA) (Huang et al.,
2023b).