Vegetation degradation in the alpine meadows is becoming increasingly severe under global change, with species loss frequently linked to changes in plant functional groups (PFGs). Changes in PFGs alter plant-derived carbon inputs, which significantly influence soil organic carbon (SOC) sequestration and soil communities. However, the impact of specific PFG removal on soil carbon fractions and nematode trophic groups remains underexplored. In this study, above-ground removal of PFGs was carried out for five consecutive years in the Qinghai–Tibet Plateau alpine meadow, with five treatments: (1) no removal of PFGs (CK); (2) keep non-legume forbs (remove graminoids and legumes, Forbs); (3) keep graminoids (remove legumes and non-legume forbs, Graminoids); (4) keep legumes (remove non-legume forbs and graminoids, Legumes); (5) remove all PFGs (All-plants-removed). Root properties, nematode community, and soil carbon fractions were measured. We found that the Graminoids treatment significantly increased root biomass, whereas the All-plants-removed treatment led to a significant decrease. Nematode abundance was highest under the Legumes treatment, primarily due to increased omnivores-predators. Meanwhile, the soil particulate organic carbon (POC) varied significantly between PFG types, being the highest in the Forbs and CK treatments. Correlation analysis revealed a significant positive relationship between SOC and bacterivore abundance, suggesting that higher SOC enhances bacterivore populations and subsequently influences carbon cycling. We conclude that PFG removal alters soil nematode community structure and POC, underscoring the role of PFGs in below-ground biodiversity and soil carbon sequestration.

Plant invasions pose a significant threat to plant community integrity at high latitudes and altitudes, particularly under the backdrop of ongoing climate change and anthropogenic disturbance. However, how plant invasion and increasing invasion intensity reshape community functional traits and multidimensional diversity in high-altitude wetland ecosystems remain poorly understood. Here, we conducted a field survey across 284 quadrats in a subalpine wetland of Shennongjia National Nature Reserve, China. Nine invasive plant species were detected and occurred in 51.06% of all sampled quadrats. We compared functional trait composition between invaded and uninvaded communities and assessed species, functional, and phylogenetic diversity along invasion intensity gradients through inclusion and exclusion models of invasive species. Invaded communities showed 9.1% higher chlorophyll content and 30.7% larger specific leaf area but 26.1% lower leaf density than uninvaded communities. In addition, community-weighted traits and diversity indices showed stronger responses when invasive species were included. With increasing invasion intensity, species diversity and phylogenetic diversity declined, whereas functional richness increased. These results demonstrate that plant invasion simultaneously drives species loss and functional reorganization, reshaping both the functional composition and biodiversity of subalpine wetland communities. Our findings highlight how invasive species restructure plant communities in subalpine wetlands, with important implications for biodiversity conservation in high-altitude ecosystems.