Plant secondary succession has been explored extensively in restoring degraded grasslands in semiarid or dry environments. However, the dynamics of soil microbial communities and their interactions with plant succession following restoration efforts remain understudied, particularly in alpine ecosystems. This study investigates the interplay between soil properties, plant communities, and microbial populations across a chronosequence of grassland restoration on the Qinghai–Tibet Plateau in China. We examined five succession stages representing artificial grasslands of varying recovery durations from 0 to 19. We characterized soil microbial compositions using high-throughput sequencing, enzymatic activity assessments, and biomass analyses. Our findings reveal distinct plant and microbial secondary succession patterns, marked by increased soil organic carbon, total phosphorus, and NH₄⁺-N contents. Soil microbial biomass, enzymatic activities, and microbial community diversity increased as recovery time progressed, attributed to increased plant aboveground biomass, cover, and diversity. The observed patterns in biomass and diversity dynamics of plant, bacterial, and fungal communities suggest parallel plant and fungal succession occurrences. Indicators of bacterial and fungal communities, including biomass, enzymatic activities, and community composition, exhibited sensitivity to variations in plant biomass and diversity. Fungal succession, in particular, exhibited susceptibility to changes in the soil C: N ratio. Our results underscore the significant roles of plant biomass, cover, and diversity in shaping microbial community composition attributed to vegetation-induced alterations in soil nutrients and soil microclimates. This study contributes valuable insights into the intricate relationships driving secondary succession in alpine grassland restoration.

Plastic film mulching is widely used in water and temperature-limited regions to enhance crop yields. Phosphorus (P) fertilization can address deficiencies in soil P availability. In this four-year field experiment conducted in an alpine agricultural area, we explored the effects of nitrogen (N) and P supply imbalance on faba bean cultivation, particularly examining intensified N competition between soil microbes and plants. The randomized block design comprised three film mulching treatments—no film mulching with flat planting (NMF), double ridges and furrows mulched with one plastic film (DRM), and three ridges and furrows mulched with one plastic film (TRM)—and three P levels—P₀ (0 kg P ha⁻¹), P₁ (9.10 kg P ha⁻¹), and P₂ (18.2 kg P ha⁻¹). The results indicated that NMF enhanced soil available N and microbial biomass N (MBN) during early growth stages, consequently improving faba bean yield, nodule weight, total N, and microbial biomass carbon (MBC) compared to DRM and TRM. DRM and TRM exhibited higher soil available N and MBN during later growth stages and higher soil temperature and water content, soil water storage (SWS), soil organic C (SOC), and soil C/N ratio than NMF. In NMF and DRM, P fertilization increased grain yield, nodule weight, SOC, total N, soil C/N ratio, soil available N, and MBC but decreased MBN during early growth stages, and decreased soil water content and SWS. TRM exhibited the opposite trend. P fertilization increased soil total P and available P. Overall, NMF combined with P fertilization (~18.2 kg P ha⁻¹) significantly improved faba bean yield. However, it may also accelerate SOC decomposition, highlighting the need to consider N fertilizer application in this alpine agricultural region.

Rational agronomic practice enhances crop productivity and resource use efficiency. Plastic film mulching and phosphorus (P) fertilization are widely applied in alpine agriculture to improve soil water content, temperature, and P availability. However, their effects on soil P transformation and nutrient uptake in faba bean (Vicia faba L.) remain unclear. This study conducted a field experiment to explore the effects of mulching methods and P levels on soil P fractions and nitrogen (N), P uptake in faba bean. The experiment followed a randomized block design with three film mulching treatments—no-mulching with flat planting (NMF), double ridges and furrows mulched with one film (DRM), and three ridges and furrows mulched with one film (TRM) and three P levels—P0 (0 kg P ha⁻¹), P1 (9.10 kg P ha⁻¹), and P2 (18.2 kg P ha⁻¹). The results showed that soil medium- and highly active P increased, while low-active P decreased with increasing P levels. Compared with DRM and TRM, NMF had lower low-active P and higher medium- and highly active P, particularly under P2. These changes contributed to increases in soil total P and available P. The aboveground N, P uptake and N/P ratio under NMF were significantly higher than under DRM and TRM. As P levels increased, the aboveground N, P uptake and N/P ratio increased in NMF and DRM, but decreased in TRM. In all treatments, the aboveground N/P ratio was below 14, indicating N limitation. NMF, especially with P2, alleviated N limitation to faba bean growth. Overall, NMF combined with about 18.2 kg P ha⁻¹ P fertilizer is a sustainable practice for faba bean cultivation in alpine regions. However, attention should be paid to achieving a balanced supply of N and P fertilizers.