Fig. 1

Sampling sites location (a). The left image shows the sampling sites in Arcgis, and the figure to the right is the remote sensing image (b). A four-point sampling quadrat used in our study (c). Seven groups sieved soil samples. The particle size ranges of soil samples from left to right in the figure are < 2.0mm, 1.0\(-\)2.0 mm, 0.5\(-\)1.0 mm, 0.25\(-\)0.50 mm, 0.15\(-\)0.25 mm, 0.09\(-\)0.15 mm, and < 0.09 mm