The impact of composite improvement measures on soil properties and vegetation characteristics of degraded natural grasslands in Karst mountainous areas

Composite improvement measures play a crucial role in promoting ecosystem restoration of degraded natural grasslands. We studied the differences in the soil properties and vegetation characteristics under different treatments, i.e., organic fertilizer + land drill + complementary seeding, organic fertilizer + sheep camping + complementary seeding, organic fertilizer + cutting root + complementary seeding and control (CK), through field investigation, physicochemical analysis, and high-throughput sequencing technology to explore the impact of different composite improvement measures on the soil properties and vegetation characteristics of degraded natural grasslands in karst mountainous areas. The results indicated that: 1) Compared to CK, the total nitrogen, total potassium, and available potassium in the soil under the three treatments were significantly increased (P < 0.05), and soil ammonium nitrogen and nitrate nitrogen were significantly reduced (P < 0.05). Soil urease activity was significantly increased (P < 0.05). Although the contents of soil microbial biomass carbon, microbial biomass nitrogen, and microbial biomass phosphorus increased to certain degrees, the difference was not significant (P > 0.05). 2) Compared with CK, the Chao index of fungal richness significantly increased (P < 0.05), while the Simpson index significantly decreased (P < 0.05). 3) Compared with CK, species richness, grass yield (green), and the proportion of leguminous forage significantly increased (P < 0.05), and the proportion of miscellaneous grass decreased significantly (P < 0.01). In summary, the three composite improvement measures could, to some extent, improve the soil fertility of degraded natural grasslands, the structure of grass communities, and grass yield. However, it is necessary to comprehensively consider factors such as the optimal fertilization amount, complementary seeding amount, and labor cost in future promotional practices.