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

AbstractQuestions: What are the water economy strategies of the dominant subarcticbryophytes in terms of colony and shoot traits? Can colony water retentioncapacity be predicted from morphological traits of both colonies and separateshoots? Are suites of water retention traits consistently related to bryophytehabitat and phylogenetic position?Location: Abisko Research Station, North Sweden.Methods: We screened 22 abundant subarctic bryophyte species from diversehabitats for water economy traits of shoots and colonies, including desiccationrates, water content at field capacity, volume and density (mgcm 3 )ofwater-saturated and oven-dried patches, evaporation rate (g 1m 2 s )andcellwallthickness.Therelationshipsbetweenthesetraitsandshootandcolonydesiccationrates were analysed with Spearman rank correlations. Subsequent multivariate(cluster followed by PCA) analyses were based on turf density, turf and shootdesiccation rate, cell wall thickness and amount of external and internal water.Results:Individualshootproperties,i.e.leafcellwallproperties,waterretentioncapacity and desiccation rate, did not correspond with colony water retentioncapacity. Colony desiccation rate depended on density of water-saturatedcolonies, and was marginally significantly negatively correlated with speciesindividual shoot desiccation rate but not related to any other shoot or colonytrait. Multivariate analyses based on traitsassumed to determine colony desicca-tion rate revealed six distinct species groups reflecting habitat choice andphylogenetic relationships.Conclusions: General relationships between shoot and colony traits as deter-minants of water economy will help to predict and upscale changes inhydrological function of bryophyte-dominated peatlands undergoing climate-induced shifts in species abundance, and feedbacks of such species shifts onpermafrost insulation and carbon sequestration functions.IntroductionBryophytesareimportantcomponentsofmany ecosystems.Their relative abundance often exceeds that of vascularplants and Sphagnum species in particular create a specificenvironment in extensive peatland areas (Longton 1997;Vitt 2000; Rydin & Jeglum 2006; Cornelissen et al. 2007).When abundant, bryophytes contribute considerably toforest evapotranspiration (Heijmans et al. 2004) and regula-tion of ecosystem hydrology (Clymo & Hayward 1982;Beringer et al. 2001), control carbon regulation (Goulden C Bisbee et al. 2001; Bergeron et al. 2009), modifysoilprocessesandmicrobialactivity(Gornalletal.2007)andcreate a microenvironment for vascular plant germination(Serpe et al. 2006) and growth (Groeneveld et al. 2007).