[Effects of Land Use Change on Constitution, Stability, and C, N, P Stoichiometric Characteristics of Soil Aggregates in Southwest China Karst].

Responses of soil aggregate stability and nutrient stoichiometry to land use change are of great significance to the protection and restoration of fragile ecosystems. In order to explore the influence of the law of land use change on soil aggregate stability and C, N, and P nutrient stoichiometric characteristics in the karst ecosystem of Southwest China, a typical region of the Southwest China Karst was selected as the study area. A series of sample plots were established for the seven typical land use types, and the constitution; stability; and C, N, and P contents and stoichiometric ratios of soil aggregates were studied. The results showed that land use change significantly affected the soil aggregate stability. The soil aggregate stability of corn fields and abandoned land was relatively high, whereas that of grassland and bare land was relatively low. The soil aggregate stability generally decreased with the increase in soil layer. There were significant differences in the C, N, and P contents of soil aggregates between different land use types. The C and N contents of soil aggregates of open woodland and abandoned land were higher, the C and N contents of grassland were lower, and the P contents of soil aggregates of bare land and abandoned land were relatively higher. Land use change also significantly affected the stoichiometric ratio of soil aggregate C, N, and P. The C:N of soil aggregates of arbor forest land, open forest land, and abandoned land was relatively high, and that of grassland was the lowest. The C:P of soil aggregates of arbor woodland and open woodland was higher than that in shrub woodland and grassland. The soil aggregate N:P of arbor forest land, open forest land, and shrub forest land was higher and was significantly higher than that of bare land and abandoned land. There were significant or extremely significant correlations between the constitution and stability of soil aggregates and the stoichiometric characteristics of soil aggregate C, N, and P. Soil aggregate stability was positively correlated with the mass fraction of large soil aggregates. The mass fraction of large soil aggregates increased, and the stability of aggregates correspondingly increased, which was conducive to the maintenance and accumulation of soil C, N, and P nutrients. These results are of great significance for vegetation restoration, soil and water conservation, and land use regulation in karst ecosystems of Southwest China.