Fractal scaling of particle-size distribution and associations with soil properties of Mongolian pine plantations in the Mu Us Desert, China

Mongolian pine plantations (MPPs) composed of Pinus sylvestris var. mongolica (P. sylvestris) are used for desertification control and restoration of degraded land in arid and semi-arid regions. We studied soil changes associated with P. sylvestris by comparing top (0–20 cm) and sub-top (20–40 cm) soil properties across 8 stand density gradients of MPPs ranging from 900 ± 5–2700 ± 50 trees ha(–1). The study was conducted in the uncovered Sandy Land in the southern Mu Us Desert, China. The relationships between the volume fractal dimensions (D) of soil particle size distribution and soil physicochemical properties were evaluated. D was determined using a laser diffraction technique and soil properties were measured. In the top layer, P. sylvestris significantly positively affected soil physicochemical properties except for bulk density and total nitrogen. These effects were not observed in the sub-top soil layer. D values ranged from 1.52 ± 0.29–2.08 ± 0.06 and were significantly correlated with stand density. Significant correlations were observed between D and soil properties (except total nitrogen) in the top soil layer. Given these results, we concluded that D is a sensitive and useful index because it quantifies changes in soil properties that additionally implies desertification in the studied area.