A systematic understanding of the spatial and temporal changes of grassland fractional vegetation cover (FVC) in Xinjiang and its drivers provide scientific reference for regional ecological restoration. In this study, we used MODIS EVI data from 2000 to 2023 and the Pixel binary model to estimate the grassland FVC value of Xinjiang; analyze its spatiotemporal dynamics with combination of trend and persistence detection methods; and explore its driving factors with ridge regression and residual analysis. The results show the following: (1) From 2000 to 2020, the grassland FVC in Xinjiang experienced an upward trend on the whole, yet a significant decrease after 2020. Spatially, the distribution characteristics are high in the northwest and low in the southeast, decreasing from mountains to basins. (2) Precipitation and soil moisture affected FVC positively, with contributions of 18.6% and 38.3%, respectively, while air temperature and solar radiation affected it negatively, with contributions of 22.9% and 20.2%, respectively. (3) The change in the grassland FVC in Xinjiang resulted from a combination of climatic factors and human activity, whose relative contribution rates were 57.2% and 42.8%, respectively; furthermore, the areas with positive effects on the FVC were smaller than those with negative effects. (4) While the FVCs of most grassland types in Xinjiang were dominantly influenced by both climatic factors and human activity, climatic conditions were the dominant drivers of the FVCs of temperate typical grasslands and temperate desert grasslands, whereas human activities had more influence on the FVC of temperate meadow grasslands. This study provides a scientific basis and guidance for optimizing the ecological barrier function and regulating vegetation coverage in arid areas by analyzing the spatiotemporal dynamics of grassland coverage in Xinjiang and quantifying the impact of different environmental factors on it.

Permafrost wetlands are important components of the global carbon cycle, functioning as carbon stores while also releasing methane (CH₄). Although biochar amendment has been proposed as a strategy to mitigate greenhouse gas (GHG) emissions, its effectiveness in permafrost wetland soils under contrasting moisture regimes remains uncertain. We conducted a 100-day incubation experiment to examine the effects of pine-sawdust biochar produced at 300 or 800 °C and applied at five rates (0%, 1%, 3%, 5%, and 8%, w/w) on soil properties, enzyme activities, and CO₂ and CH₄ emissions under non-flooded and waterlogged conditions. Biochar addition altered soil pH, carbon and nitrogen pools, and enzyme activities, with responses varying between moisture regimes. Under non-flooded conditions, 300 °C biochar reduced soil pH and increased nitrate nitrogen (NO₃⁻-N), whereas under waterlogged conditions, biochar treatments increased soil pH and were associated with higher ammonium nitrogen (NH₄⁺-N) and lower NO₃⁻-N concentrations. Biochar generally reduced CO₂ emissions under non-flooded conditions and CH₄ emissions under waterlogged conditions. The 8% amendment of 800 °C biochar under waterlogged conditions yielded the lowest reported global warming potential (GWP; 5.49 ± 0.15 g·kg⁻¹). Enzyme responses also depended on moisture regime: dehydrogenase and urease activities generally declined under waterlogged conditions, whereas 300 °C biochar increased catalase activity. Pearson correlation and SHapley Additive exPlanations (SHAP) analyses identified NH₄⁺-N (29.3%) and catalase activity (17.4%) as the two leading predictors of GWP in the fitted model. These findings suggest that biochar amendment can reduce GHG emissions during laboratory incubation, although the magnitude and direction of the response depend on pyrolysis temperature, application rate, and moisture regime. Among the treatments tested, the 8% amendment of 800 °C biochar under waterlogged conditions produced the lowest GWP.

The forest soil carbon represents the largest carbon pool in the terrestrial ecosystem. To clarify the effect of climate warming on the soil carbon pool of a Pinus tabulaeformis plantation in the northern temperate zone, an open-top chamber was used to study the effects of warming on soil temperature and moisture, soil enzyme activity, soil active organic carbon, and greenhouse gas emissions in different soil layers. The results showed that (1) warming increased the temperature and decreased the moisture content of the atmosphere and soil. Atmospheric temperature increased by 0.9 °C on average, and atmospheric moisture decreased by 0.05%. The average annual temperatures of the surface soil (5 cm) and deep soil (40 cm) increased by 1.18 and 0.66 °C, respectively, and soil moisture decreased by 2.55% on average. (2) Warming had no significant effect on soil active organic carbon or enzyme activity, but had a significant effect on the active organic carbon content and enzyme activity in individual soil layers in individual months. For example, warming significantly altered the soil sucrase and catalase activities in the 10–20 cm soil layer in September, and also had a significant effect on readily organic carbon content in the 10–20 cm soil layer in July. (3) The seasonal variation of soil CO₂ flux showed a unimodal pattern, peaking in July and, ranging from 116.75 to 420.45 mg·m⁻²·h⁻¹. Warming reduced soil CO₂ emissions from the control treatment, from 996.35 to 781.57 g·m⁻². The soil of the P. tabulaeformis forest in Daqing Mountain is a sink of atmospheric CH₄. The seasonal variation range is −32.34 to −76.43 µg·m⁻²·h⁻¹, and the flux value is at its lowest in September. Warming promoted the absorption of soil CH₄, and the seasonal absorption values of CH₄ in the warming and control treatments were 172.03 and 136.90 mg·m⁻², respectively. Therefore, after the short-term warming treatment, the soil moisture was reduced; greenhouse gas emissions were significantly reduced, and the warming formed a negative feedback with soil greenhouse gas flux.