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.

Quantifying the spatiotemporal patterns of the coordination between ecosystem service supply and demand is vital for regional sustainable development. To reveal the dynamic pattern of the coordination of ecosystem service (ES) supply and demand in the Lhasa River Basin, we quantified the supply of the following four ESs using the InVEST model from 2000 to 2018: carbon sequestration (CS), water conservation (WC), habitat quality (HQ), and soil conservation (SC). Using socio-economic data, including land development degree, GDP, and population density, the ES demand was quantified. The ES supply–demand ratio (ESDR) and coupling coordination degree (CCD) model were used to evaluate the coupling relationship and coordination of ES supply and demand. The spatial autocorrelation analysis was used to determine the spatial correlation and changes in the ES supply–demand coupling coordination degree. The results indicate that the distribution of ESDR exhibited significant spatial heterogeneity. The area with ES supply far greater than demand was always in the upstream area of the Lhasa River, while the ES demand of Chengguan District far exceeded supply. Grasslands and forests were the main contributors to ESDRs, providing positive ESDRs for three services, SC, HQ, and WC, with a total proportion above 80%. From 2000 to 2018, the mismatch between ES supply and demand was gradually spreading upstream, while the upstream areas had a relatively high CCD. The spatial correlations of the CCD in the Lhasa River basin all showed statistically significant differences (p < 0.01). The high–high aggregation areas were concentrated in the northeast of the Lhasa River basin, while the low–low aggregation areas were centered around Chengguan District. This study provides reference values for optimizing the land use spatial patterns in ecologically vulnerable areas with the goal of sustainable development.