Abstract:
It is important to study how slope aspect and position affect the stability of soil aggregates for understanding the maintenance of soil stability in alpine and gorge region with complex geomorphology. However, the research on soil characteristics of alpine shrub is relatively scarce at present. In this paper, we studied the particle size distribution, stability, and fractal characteristics of soil aggregates of shrub communities in different slope aspects and positions in Jiajin Mountains, and we conducted a partial least square path model (PLS-PM) to analyze the function mechanism of slope aspect and position on soil aggregate stability. At the same time, the relationship between the fractal dimension and the stability of the aggregates was discussed. The results show that: ① The particle size distribution of mechanical stability of soil aggregates is only affected by the slope aspect, while the particle size distribution of soil water-stable aggregates is affected by the slope aspect, slope position and the interaction of the two. ② The stability of soil aggregates in the middle slope is better than that in the lower slope, and the stability of soil aggregates in the shady slope is the lowest among the three slope aspects. ③ Soil aggregates are mainly affected by the slope aspect, which is mainly determined indirectly by the effect of the slope aspect on soil physical properties (soil bulk density, moisture content, and porosity). Meanwhile, slope aspects have a certain effect on the stability of soil aggregates by influencing the characteristics of shrub communities (abundance, richness and biomass), and acting on soil chemical properties (TN, TP, TK, SOM, and pH). The characteristics of herb communities affected by slope aspect shows no effect on soil physicochemical properties and aggregate stability. ④ It is feasible to use soil fractal dimensions to characterize soil aggregate stability.