Stability and Erodibility of Aggregate Affected by Typical Tree-herb Ecosystems in Karst Area

Objective The aim was to explore short-term effects of tree-herb ecosystems on soil aggregate characteristics, in order to provide a theoretical basis for a comprehensive assessment of the ecological and economic effects of vegetation restoration transitions in karst regions.

Methods Four tree-herb ecosystems based on Prunus salicina were selected, including Prunus salicina + Rubus chingii, P. salicina + Polygala fallax, P. salicina + Hypericum monogynum, and P. salicina + Semiliquidambar cathayensis + Illicium difengpi. Monocultures of P. salicina were used as controls. These ecosystems were compared in terms of soil aggregate composition, stability, erodibility, and their relationship under sand removal and sand inclusion treatments.

Results ① Tree-herb ecosystems facilitated the conversion of microaggregates (< 0.053 mm) into macroaggregates (> 2 mm), irrespective of sand extraction. ② Tree-herb ecosystems, particularly the P. salicina + H. monogynum system, increased the mean weight diameter, geometric mean diameter, and content of water stable aggregates > 0.25 mm within soil aggregates, but decreased the fractal dimension and erodibility factor. Meanwhile, a significant negative correlation was found between the comprehensive score of soil aggregate stability and erodibility. ③ The presence of sand led to a slight overestimation of the soil structure characteristic parameters in each ecosystem compared with the treatment involving removal of sand.

Conclusion Tree-herb ecosystems, especially P. salicina + H. monogynum system, have a positive effect on soil aggregate stability and erodibility, but the number of plant species and the complementarity of the configuration and an optimal combination should be considered in constructing ecosystems. Meanwhile, future studies should accurately assess the soil structure function in order to correct the soil sand content in karst regions.