The Qinghai-Tibetan Plateau (QTP) has the world’s largest alpine grassland ecosystem. The QTP ecosystem is extremely fragile and suffers continuous degradation. An accurate determination of the status of alpine grassland is the first crucial step in monitoring its degradation. A novel method combining field survey with remote sensing information based on ecological indicators is proposed. The degradation classification of alpine grassland was identified by multivariate hierarchical analysis based on 270 field plots. The spatial pattern of alpine grassland degradation was mapped by determining remote sensing variables that corresponded to field indicators of the degradation classification system. The results showed that clustering analysis divided the degradation classification of alpine grassland into five classes: Non-Degraded (ND), Slightly Degraded (SLD), Moderately Degraded (MD), Severely Degraded (SD), and Extremely Degraded (ED). The most significant factors for alpine grassland degradation included the dominance of Cyperaceae plants, soil total nitrogen content, soil organic carbon content, soil total carbon content, soil bulk density, soil pH, dominance of miscellaneous plants, and elevation among all 17 variables. The assessment and mapping of alpine grassland degradation provide an important basis for alpine grassland protection and management, particularly at a large scale.

China plans expanding 49.5 million hectares of new forests by 2050 to strengthen carbon sequestration. However, estimates of the carbon benefits from this expansion rarely consider the effect of ‘forest edge’, where tree mortality increases under intensified stress from wind, drought, pests, and fire. Here we show that proximity to forest edges substantially reduces biomass carbon storage, and develop a spatial optimization strategy that prioritizes planting in areas that minimize edge effects. Our projections show that forestation optimized for edge effects results in a 51% increase in carbon gain (986 ± 22 Tg by 2060), with approximately half of the total gain driven by reduced edge effects. These findings demonstrate that ignoring edge effects can significantly overestimate carbon sink potential and highlight spatially optimized forestation as a pathway to maximize climate mitigation and ecological benefits.

Forest gaps play an important role in species regeneration and forest succession. Gap size has a primary influence on tree species coexistence and community assembly along an elevation gradient. In this study, we evaluated the regeneration and coexistence of Abies faxoniana, Betula utilis, and Acer maximowiczii at different life history stages in varied gap sizes along an elevation gradient (between 3000 and 3500 m a.s.l). We found that gap size can positively enlarge the effects of elevation on the regeneration density of the three species. In the process of regeneration from seedling to sapling, Abies had stronger regeneration capability, with regeneration niche breadths of more than 0.6 in different gap sizes. A factor analysis of mixed data indicated that regeneration density, soil nutrient contents, and air humidity were mainly related to gap size, but habitat temperature was largely determined by elevation. The connection between the species regeneration density and habitat conditions was due to differences in their regeneration niches, reflecting the selective preemption of environmental resources of different species in different life stages. Microhabitat heterogeneity, controlled by the characteristics of forest gaps along an elevation, affected the regeneration niche differences of the tree species, which contributed to the species coexistence and community assembly processes.