Precipitation variability profoundly influences soil microbial diversity, community assembly processes, and co-occurrence networks. However, the responses of soil microbial structure to relative precipitation changes in alpine regions remain uncertain. To address this, we conducted a two-year field precipitation manipulation experiment in alpine steppe and alpine desert steppe ecosystems at the source of the Yarlung Zangbo River on the Tibetan Plateau. The experiment simulated 25%, 50%, and 75% increases and decreases in precipitation to examine how soil microbial communities respond to altered precipitation regimes. Our results reveal that microbial responses varied with precipitation magnitude, grassland type, and microbial kingdom. In the alpine steppe, bacterial α-diversity exhibited a negative asymmetric response to altered precipitation at both species and phylogenetic levels. Both bacterial and fungal species α-diversity tended to respond more strongly to changes in precipitation at high gradients in the alpine steppe than in the alpine desert steppe. Microbial co-occurrence networks in the alpine steppe were generally more responsive to altered precipitation than those in the alpine desert steppe. Furthermore, fungal α-diversity at both species and phylogenetic levels, as well as β-diversity, responded more strongly to altered precipitation than bacterial communities. These findings suggest that precipitation-driven shifts in microbial community composition and network structure vary across alpine grassland ecosystems, with fungal communities exhibiting greater sensitivity than bacterial communities. As warming intensifies precipitation variability, these microbial shifts may have cascading effects on soil biogeochemical processes and ecosystem stability, underscoring the necessity for ecosystem-specific conservation frameworks and adaptive management strategies tailored to alpine grasslands.

Alpine agroecosystems face fertilizer-induced nutrient imbalances, including early nitrogen accumulation and late-season nitrate residue. While organic substitution is promoted as a sustainable practice, different substitution ratios may generate contrasting responses among nutrient availability, rhizosphere function, and SOC temporal stability. We established a field experiment in Tibetan highland barley with five treatments at equivalent N, P, and K rates: 100% NPK, 75% NPK + 25% cattle manure (CM), 50% NPK + 50% CM, 25% NPK + 75% CM, and 100% CM, plus an unfertilized control. Soils were sampled from 0–10 cm bulk soil, 10–20 cm bulk soil, and rhizosphere soil (0–10 cm) at booting, filling, and maturity. Stoichiometric ratios in the 0–10 cm layer changed mainly at maturity, whereas responses in the 10–20 cm layer and rhizosphere were weaker, indicating stage- and compartment-dependent treatment responses. The treatments showed three response modes: mineral fertilizer-dominated nutrient pulses, manure-dominated late-season nitrate residue and surface SOC stability, and partial substitution patterns with comparatively balanced nutrient responses. No single substitution ratio optimized all measured indicators. We therefore propose these modes as a framework for organizing treatment-specific nutrient responses and as candidates for further multi-year and multi-site testing, rather than as ready-to-apply fertilization prescriptions.

The soil microbial functional community is a better predictor of ecosystem processes under global change. However, the responses of the soil microbial functional community structure to short-term nitrogen (N) and phosphorus (P) additions remain unclear. Here, we carried out an experiment exploring the effects of N and P additions on soil fungal and bacterial functional diversity and community composition in an alpine steppe on the Tibetan Plateau. The results showed that soil fungal functional α-diversity significantly decreased under N or P addition, whereas soil bacterial functional α-diversity did not change. Furthermore, soil bacterial functional group aerobic nitrite oxidation increased significantly under combined N and P additions, but soil bacterial and fungal community composition and β-diversity did not change. Further analysis illustrated that soil available nitrogen was the main factor leading to the changes in soil fungal functional α-diversity and soil bacterial functional groups under N and P additions. Therefore, we should give importance to the potential influence in view of future increasing N and P deposition on the soil microbial functional community in the alpine grassland on the Tibetan Plateau, which will be beneficial for the prediction of soil biogeochemical cycles and guiding ecosystem management.