Effects of plant patches on soil aggregates in the Hilly Loess Plateau region

During a restoration of an abandoned slope land in the Hilly Loess Plateau region, a mosaic pattern of plant patches and bare land patches was gradually established on the slope during vegetation succession. This pattern has potential effects on the organic matter, aggregate stability, and spatial heterogeneity of the soil. In this study, we used Artemisia gmelinii and Bothriochloa ischaemum communities from both patches as study models. Soil samples were collected from plant patches and bare land patches for soil aggregate and organic matter content analysis. The results showed that the proportion of large aggregates (particle size > 2 mm), mean weight diameter (MWD), geometric mean weight diameter (GMD), and soil organic matter content were higher in plant patches compared to bare land patches. However, the fractal dimension of aggregates was lower in plant patches. Large aggregates in plant patches accounted for 64.2% of A. gmelinii communities and 70.6% of B. ischaemum communities but only made up 49.5% and 45.9% in the respective communities in bare land patches. Wet sieving showed a maximum MWD of 1.296 mm and a maximum organic matter content of 16.137 g·kg⁻¹ in B. ischaemum patches. The fractal dimension in plant patches decreased by 6.7% and GMD increased by 22.6% compared to their proportions in bare land patches. These results indicate that perennial grass species with fibrous root systems, such as B. ischaemum, play a significant role in improving soil stability and that plant patch development, in general, may promote soil stability.