not-yet-known not-yet-known not-yet-known unknown Understanding soil nitrogen (N) processes and their response to climate change across diverse land-use types is crucial for bolstering the ecosystem functionality and stability, and also vital for refining land management strategies, especially as oasis expansion and land development practices become more frequent and widespread in dryland regions. We conducted a field soil sample collection and laboratory incubation experiment to examine the response of soil nitrogen mineralization to temperature and moisture across four land-use types in a typical dryland area of northwestern China. The mean values of soil net nitrification, ammonification, and mineralization rates across all treatments were 1.27 (0.43–3.01), –0.24 (–0.60–0.58), and 1.03 (–0.10–2.88 ) mg N kg -1 day -1, respectively. Notably, an increase in temperature and moisture substantially enhanced soil net nitrification rates by 3.7–104.2% and 26.0–72.0%, respectively. Conversely, the net ammonification rate declined, ranging from 30.0 to 94.4% with temperature changes and 10.7 to 137.5% with moisture variations. Among the land-use types examined, Poplar shelterbelt forests exhibited the highest soil N mineralization rate, followed by reclaimed farmlands, Gobi desert grasslands, and artificial sand-fixing shrubs. Notably, land-use changes significantly modulated the sensitivity of soil N mineralization rate to temperature and moisture. Specifically, its responses to temperature and moisture were strong in poplar shelterbelt forests and reclaimed farmlands but weak in Gobi desert grasslands and artificial sand-fixing shrubs. This study underscores the pivotal role of substrate quantity in determining the response of soil N mineralization rates to temperature and moisture fluctuations. Therefore, we posit that resilient ecosystems that respond positively to environmental perturbations, particularly variations in temperature and moisture, are more likely to enhance productivity by modulating soil N available. In contrast vulnerable ecosystems that consistently maintain a low soil N levels, regardless of environmental fluctuations, may face constraints in their development and improvement potential.

Patterns and elevational controls on the response of soil organic matter (SOM) decomposition to temperature in alpine forest soils are critical to efforts to quantify the regional carbon cycle-climate feedback, but are not well known. Here, we report rates of soil organic matter (SOM) decomposition (Rs) and temperature sensitivity (Q10) determined in a short-term laboratory incubation with a gradual warming from 5°C to 29°C of soils from different elevations in the Qilian Mountains, China (2,600, 2,800, 3,000, and 3,200 m). The results showed the Rs significantly increased with increasing elevation (P<0.001). Across all elevations, RS first showed an increasing trend at temperatures < 20 ℃ and then declined substantially, most likely in response to the content of labile C (greater at the start of incubation, and declining over time). Q10 of SOM decomposition increased significantly with increasing elevation and deceasing incubation temperature (P<0.001). More importantly, soil organic carbon (SOC), total nitrogen (TN), 1-2 mm aggregate-associated OC, and elevation were the main control factors affecting Rs and Q10. These results indicate that high-altitude soils in alpine forests of the Qilian Mountains are relatively more sensitive to temperature changes, and have greater potential to release CO2 due to higher SOC contents and 1-2 mm aggregates-associated OC than low-altitude. The findings could serve as a reference for how regional C pools may respond to future warming in alpine forests of the Qilian Mountains.

Lacking of systematic evaluations in soil quality and microbial community recovery after different amendments addition limits optimization of amendments combination in coal mine-soils. We performed a short-term incubation experiment over 12 weeks to assess the effects of three amendments (biochar: C; nitrogen fertilizer at three levels: N-N1~N3; microbial agent at two levels: M-M1~M2) based on C/N ratio (regulated by biochar and N level: 35:1, 25:1, 12.5:1) on soil quality and microbial community in the Qilian Mountains, China. Over the incubation period, soil pH and MBC/MBN were significantly lower than unamended treatment in N addition and C+M+N treatments, respectively. Soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents had a significant increase in all amended treatments (P<0.001). Higher AP, AK, MBC, MBN and lower MBC/MBN were observed in N2-treated soil(corresponding to C/N ratio of 25:1). Meanwhile, N2-treated soil significantly increased species richness and diversity of soil bacterial community (P<0.05). Principal coordinate analysis further showed that soil bacterial community compositions were significantly separated by N level. C-M-N treatments (especially at N2 and N1 levels) significantly increased the relative abundance (>1%) of the bacterial phyla Bacteroidetes and Firmicutes, and decreased the relative abundance of fungal phyla Chytridiomycota (P<0.05). Redundancy analysis illustrated the importance of soil nutrients in explaining variability in bacteria community composition (74.73%) than fungal (35.0%). Our results indicated that N and M addition based on biochar can improve soil quality by neutralizing soil pH and increasing soil nutrient contents, and the appropriate C/N ratio (25:1: biochar+N2-treated soil) can better promote mass, richness and diversity of soil bacterial community. Our study provided a new insight for achieving restoration of damaged habitats by changing microbial structure, diversity and mass by regulating C/N ratio of amendments