Effects of forest-grass intercropping on soil nutrient and microbial populations in Karst rocky desertification areas

Forest-grass intercropping presents numerous advantages in terms of water conservation, soil fertility enhancement, and biodiversity promotion. This method can be used as a model for ecological restoration in Karst rocky desertification areas. To investigate the influence of forest-grass intercropping on soil nutrients and microbial populations in such regions, we anlayzed three planting patterns: intercropping of Zanthoxylum bungeanum with Dolichos lablab, intercropping of Z. bungeanum with Paspalum thunbergii, and sole monocropping of Z. bungeanum. This research was conducted at a long-term experimental base in Bangui Township, Guanling County, Guizhou Province. The results demonstrated that compared with Z. bungeanum monocropping, intercropping with D. lablab and P. thunbergii led to increases in organic matter, total nitrogen, fast-acting potassium, and alkaline nitrogen in the soil. Furthermore, the soil pH decreased, and the number of soil microorganisms, particularly fungi, significantly increased. The effective phosphorus content significantly decreased in the 0－10 cm soil layer, whereas it increased in the 10－20 cm soil layer. Correlation analysis revealed a significant negative correlation between the number of bacteria in the 0－10 cm soil layer and effective phosphorus, whereas the number of fungi and organic matter, total nitrogen, effective phosphorus, and pH were significantly positively correlated. In the 10－20 cm soil layer, the number of bacteria was significantly positively correlated with fast-acting potassium, whereas the number of fungi exhibited a significant negative correlation with pH. These findings suggest that the ecological restoration model of forest-grass intercropping, composed of Z. bungeanum and forage, has positive effects on soil nutrients and microbial populations in Karst rocky desertification areas.