Walnut trees on the Tibetan Plateau have sustainable and nutritious characteristics. They grow naturally without the use of any chemical fertilizers and pesticides. Therefore, the soil fertility of walnut orchards is a key factor influencing walnut yield and quality. This experiment measured and analyzed the basic soil nutrient content, microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and leaf nutrient indicators in five types of representative walnut orchard soil parent materials in Gyaca County to clarify the fertility characteristics of different soil types and their correlations with walnut nutrients, providing a basis for the sustainable development of the plateau walnut industry. The results showed that there were significant differences in soil organic matter (SOM), total nitrogen (TN), available nutrient contents, and microbial activity among soil types with different parent materials. The comprehensive representation of available nutrient levels in the soils is as follows: gray-cinnamon soil and calcareous alluvial soil > mountain meadow soil > plateau prairie soil and brush prairie soil. The average MBC, MBN, and MBP contents in the five soils were 368.8 mg/kg, 28.4 mg/kg, and 23.6 mg/kg, respectively, and the content in the topsoil (0–20 cm) was higher than that of the subsoil (20–40 cm). The total nitrogen (PN), total phosphorus (PP), and total potassium (PK) contents in walnut leaves were found to be closely related to the soil physicochemical properties and microbial activity, among which five indicators, including soil TN, available nitrogen (AN), SOM, MBC, and slowly available potassium (SAK), had the greatest impact on leaf nutrient levels. These findings are valuable for the future management and development of walnut orchards. Therefore, for different soil parent materials and soil types, improving the soil fertility and actively applying nitrogen-rich organic fertilizers should be prioritized to improve the yield and quality of Tibetan Plateau walnuts.

Land-use type is a key factor influencing soil properties, microbial community composition, and plant nutrient status. In this study, five land-use types (Tibetan barley, rapeseed, walnut, wheat, and weeds) were investigated in a river valley of southeastern Tibet to compare their effects on soil chemical characteristics, microbial communities, and plant nutrients. Soils under walnut trees had significantly higher available phosphorus and microbial biomass phosphorus but lower soil organic matter. Rapeseed fields had higher levels of available potassium and were dominated by the fungal genus Tausonia; rapeseed leaves also contained the highest nitrogen and potassium concentrations. Weed plots supported a distinct fungal community dominated by Helvella. Tibetan barley and wheat increased overall bacterial and fungal diversity, with wheat soils with the highest microbial biomass carbon and nitrogen. Redundancy analysis indicated that soil total nitrogen, available nitrogen, and organic matter were the main drivers of plant nutrient variation, together explaining 93.5% of the total variance. These findings demonstrate how land-use type regulates soil–microbe–plant interactions in alpine valleys and provide empirical references for agricultural management and soil improvement on the Qinghai–Tibet Plateau.

This study investigated the effects of three land use patterns—rice (Oryza sativa L.)–rapeseed (Brassica napus L.) rotation (Rapeseed), rice–shrimp (Procambarus clarkii G.) rotation (Shrimp), and the conversion of paddy fields to forestland (Forestland)—on aggregate structure, nutrient content, and microbial diversity in rice soils in Chuandian Town, Jingzhou District, Jianghan Plain, central China. The results revealed that the Shrimp treatment significantly increased soil organic matter (SOM), available nitrogen (AN), and available phosphorus (AP) content in the surface soil (0–10 cm) while reducing soil bulk density and improving pore structure. Forestland exhibited higher aggregate stability in deeper soil layers (20–40 cm), particularly in the 0.053–0.25 mm size fraction. Microbial diversity analysis showed that bacterial richness (Chao1 index) and diversity (Shannon index) were significantly higher in the Shrimp and Rapeseed treatments compared to those in the Forestland treatment, with Proteobacteria and Chloroflexi being the dominant bacterial phyla. Fungal communities were dominated by Ascomycota, withfForestland showing greater fungal richness in deeper soil. Soil depth significantly influenced aggregates, nutrients, and microbial diversity, with surface soil exhibiting higher values for these parameters than deeper layers. Redundancy analysis indicated that SOM, AP, and pH were the key drivers of bacterial community variation, while fungal communities were more influenced by nitrogen and porosity. Path analysis further demonstrated that land use patterns indirectly affected microbial diversity via altering aggregate structure and nutrient availability. Overall, the Shrimp treatment outperformed others in improving soil structure and nutrient supply, whereas the Forestland treatment was more conducive to promoting aggregate stability in deeper soil. Land use patterns indirectly regulated microbial communities through modifying soil aggregate structure and nutrient status, thereby influencing soil ecosystem health and stability. This study provides a theoretical basis for the sustainable management of rice soils, suggesting the optimization of rotation patterns in agricultural production to synergistically enhance soil physical, chemical, and biological properties.