Adaptations in Sphagnum functional traits in response to increased elevation in karst plateau wetlands
Description
Sphagnum functional traits serve as crucial indicators of environmental change and are essential for predicting potential alterations in wetland plant functions. However, there exists a significant knowledge gap concerning the response of Sphagnum functional traits and functions to elevation gradients in plateau wetlands. This study, therefore, focused on the functional traits and water-holding capacity (WHC) of Sphagnum mosses across eleven wetlands along an elevational gradient on the Guizhou Karst Plateau. By employing redundancy analysis (RDA), variance partitioning analysis (VPA), partial least squares structural equation modeling (PLS-SEM), and allometric models, we aimed to elucidate the trade-offs between functional traits and WHC in response to increasing elevation. The findings indicated that with increasing elevation, Sphagnum prioritized greater biomass allocation to stems over capitula, with stem leaves receiving more investment relative to branch leaves. The maximum WHC of Sphagnum and its capitula reached 55.06 and 56.60 times their dry mass, respectively. Furthermore, Sphagnum’s WHC was positively influenced by stem leaf traits but negatively affected by branch leaf traits and biomass allocation. Stem leaves accounted for 13.3% of the variation in Sphagnum's WHC－a contribution 133 times greater than that of branch leaves. We find that Sphagnum adapts to elevational gradients in karst plateau wetlands through a dual mechanism: reallocating biomass from capitula to stem and modulating stem leaf traits to enhance WHC (i.e., biomass reallocation + stem leaf trait adjustment). This study updated WHC records of Sphagnum, filled knowledge gaps regarding Sphagnum’s trade-offs in biomass allocation and leaf trait adjustments under environmental changes, highlighted the predominant role of stem leaf traits in determining WHC.