Soil physical and chemical properties
The differences in soil physical and chemical properties were compared
between farmland ecotones, residential areas, grasslands, and roadsides.
The upper 0–20 cm of soil from four habitats (selected at observation
points determined in 2010 in Experiment 1 where A. artemisiifoliaand A. trifida were present) was divided into two layers. The
soil in each 10-cm layer was sampled, and soil properties were
determined in July 2017 as follows. Total nitrogen, total phosphorus,
and total potassium were determined using the micro-Kjeldahl, sodium
hydroxide melting-molybdenum anti-colorimetric, and flame photometry
methods, respectively. Soil pH was measured using a Mettler-Toledo pH
meter (UB-10, USA), and soil conductivity was measured using a
conductivity meter (Hach, USA). Soil organic matter content was checked
using the
K2CrO7-H2SO4external heating method. Alkaline hydrolysis nitrogen, available P, and
available K were measured using the alkaline hydrolysis diffusion
method, Mo-Sb colorimetry, and the ammonium acetate method,
respectively. Soil samples from each habitat were taken three times in
three individual sites (more than 5 km apart), and a total of 3
(repetition) × 4 (habitat) × 2 (soil layer), which resulted in 24
samples being collected.