Altitude markedly influenced moss functional traits and trait associations at the community level in the eastern Pamir Plateau

Mosses, as small-sized and structurally simple terrestrial pioneer plants, have gradually developed a series of key functional traits during their long evolutionary history to cope with diverse environmental stresses. However, our understanding of the environmental variability of moss functional traits at the community level, particularly in plateau mountain systems characterized by harsh conditions, remains limited. The eastern Pamir Plateau (China) was selected as the study area, where four vertical transects spanning different altitude ranges were established. Multiple community-level physiological traits and environmental factors were measured to explore the variation patterns of moss functional traits along altitude gradients and their underlying mechanisms. The results revealed that non-structural carbohydrates, antioxidant enzymes, osmotic regulatory substances, oxidative stress products, and photosynthetic pigments of mosses exhibited significant differences across altitude gradients ( P < 0.05), showing distinct trends with increasing altitude. Plant Trait Networks (PTNs) displayed higher network densities at low- to mid-altitude ranges (2000–2500 m: 0.626; 2500–3000 m: 0.514; 3000–3500 m: 0.604), whereas the densities decreased at high altitudes (3500–4000 m: 0.343; 4000–4500 m: 0.341), indicating that PTN structures became looser with increasing altitude. Moreover, the central traits within PTNs shifted along the altitude gradient, following the order POD → Starch → MDA → SOD → SP. Hierarchical partitioning analysis showed that at 2000–3500 m, PTN central traits were primarily driven by climatic factors (38.60 %, 33.12 %, 42.14 %) and geographical-topographic factors (34.53 %, 37.40 %, 34.06 %). At 3500–4000 m, soil factors (47.68 %) and geographical-topographic factors (43.44 %) were the dominant drivers. At altitudes between 4000 and 4500 m, both climatic factors (43.55 %) and soil factors (43.01 %) jointly drive the variation. Multiple linear regression analysis further clarified the major influencing variables within each category. This study revealed systematic variations in moss functional traits and their network structures along an elevational gradient in alpine arid regions. The central trait regulatory mechanisms gradually shifted from being primarily governed by climate-topography interactions to being jointly driven by soil-climate coupling, reflecting adaptive responses of mosses to environmental gradient changes. Overall, these findings provide important insights into the functional adaptation mechanisms of moss communities in alpine arid climates and hold practical significance for ecosystem conservation in plateau regions. • This study revealed the variation patterns of moss community functional traits along different altitudinal gradients on the eastern Pamir Plateau and, for the first time, constructed their PTNs. • The PTN structure of mosses became progressively looser with increasing altitude, with central traits successively shifting from POD → Starch → MDA → SOD → SP. • Environmental drivers varied with altitude: climate and topography dominated at low–mid levels, while soil and climate jointly shaped PTNs at high altitudes. • These findings provide new insights into moss functional adaptation and ecosystem conservation in cold, arid regions.