Phenotypic plasticity of Eurohypnum leptothallum in degraded karst ecosystems: Adaptative mechanisms and ecological functions driven by warming temperatures.

Phenotypic plasticity is a critical mechanism for plants to adapt to rapid climate change and other global change drivers. Eurohypnum leptothallum is widely distributed in fragile subtropical karst ecosystems, exhibiting strong drought tolerance, water retention, and soil stabilization capabilities, playing a vital ecological role in nutrient cycling and ecological restoration. Our study investigated the specific manifestations of phenotypic plasticity in epilithic E. leptothallum within degraded karst ecosystems. Results showed that E. leptothallum exhibited high phenotypic plasticity in the heterogeneous environments of degraded karst ecosystems. In the temperature range of 21.5 °C-59.5 °C, E. leptothallum developed a set of adaptive mechanisms in response to warming temperatures through the trade-offs and combinations in most morphological traits (increasing in shoot height, stem cortical ratio and leaf middle cell lumen area, decreasing in stem diameter and stem central strand ratio, making leaf shape, cell shape and lumen shape tend to ellipse) and physiological traits (increasing in C, Ca, C:N, C:P, N:P, Fv/Fm and Y(NO), decreasing in qP). Furthermore, these phenotypic variations may confer certain ecological benefits to the degraded karst ecosystems and are expected to contribute to the maintenance and sustainable development of structural stability and species diversity in degraded karst ecosystems and even global ecosystems in the early stages of global warming. The findings provide a new perspective for exploring the response of bryophytes to environmental changes, a theoretical basis for predicting the adaptive strategies of E. leptothallum and its potential ecological functions to degraded karst ecosystems under global warming.