Functional traits variation and adaptive strategies of epilithic bryophytes in degraded karst ecosystem

Studies on the variation in plant functional traits provide an important theoretical perspective for elucidating the mechanisms of community assembly and the adaptive strategies of species to their environments. Bryophytes, as pioneer groups undergoing active succession in natural ecosystems, can exert significant ecological benefits, including water retention and soil stabilization, in the ecologically fragile karst regions of southwest China. However, studies on the variation of their functional traits are still insufficient. Therefore, this study selected Guizhou Province (Nidang Stone Forest)-one of the regions most representative of degraded karst ecosystems in Southwest China-as the study area. Focusing on epilithic bryophytes, we aimed to explore the interspecific and intraspecific variation patterns of their functional traits, as well as the adaptive strategies they use to cope with environmental stress through trait trade-offs and combinations. The results showed that the functional traits of epilithic bryophytes exhibit a trait variation pattern of “physiological convergence - morphological differentiation”. Their responses to environmental signals were associated with taking nutrient related traits (C: P ratio, C: N ratio, phosphorus content) as the key hub traits for resource transmission, and the functional integration between morphological traits (increased middle cell vertical wall thickness and middle cell width) and photosynthetic physiological traits (increased non-photochemical quenching, nitrogen content, phosphorus content, calcium content and decreased relative chlorophyll content, maximum photochemical efficiency actual photochemical efficiency of PS II, C: P ratio, C: N ratio, N: P ratio). Such trait variations may enhance nutrient immobilization, potentially contributing to the ecological restoration and sustainable development of degraded karst ecosystems. This study deepens the understanding of functional traits variation in bryophytes, thereby furnishing a theoretical basis for forecasting the adaptive mechanisms of epilithic bryophytes in response to environmental stress and their potential ecological roles across degraded karst ecosystems. It also offers a theoretical reference for the rehabilitation of these ecosystems.