The importance of colony structure versus shoot morphology for the water balance of 22 subarctic bryophyte species

Abstract

Questions: What are the water economy strategies of the dominant subarctic bryophytes in terms of colony and shoot traits? Can colony water retention capacity be predicted from morphological traits of both colonies and separate shoots? Are suites of water retention traits consistently related to bryophyte habitat and phylogenetic position? Location: Abisko Research Station, North Sweden. Methods: We screened 22 abundant subarctic bryophyte species from diverse habitats for water economy traits of shoots and colonies, including desiccation rates, water content at field capacity, volume and density (mg cm−3) of water-saturated and oven-dried patches, evaporation rate (g·m−2·s−1) and cell wall thickness. The relationships between these traits and shoot and colony desiccation rates were analysed with Spearman rank correlations. Subsequent multivariate (cluster followed by PCA) analyses were based on turf density, turf and shoot desiccation rate, cell wall thickness and amount of external and internal water. Results: Individual shoot properties, i.e. leaf cell wall properties, water retention capacity and desiccation rate, did not correspond with colony water retention capacity. Colony desiccation rate depended on density of water-saturated colonies, and was marginally significantly negatively correlated with species individual shoot desiccation rate but not related to any other shoot or colony trait. Multivariate analyses based on traits assumed to determine colony desiccation rate revealed six distinct species groups reflecting habitat choice and phylogenetic relationships. Conclusions: General relationships between shoot and colony traits as determinants of water economy will help to predict and upscale changes in hydrological function of bryophyte-dominated peatlands undergoing climate-induced shifts in species abundance, and feedbacks of such species shifts on permafrost insulation and carbon sequestration functions.