Characterizing Microclimate and Plant Community Variation in Wetlands

Groundwater-fed calcareous wetlands (fens) support diverse plant assemblages including rare species and boreal disjuncts, yet factors structuring related microclimatic and plant community variation have not been thoroughly examined. We investigated factors influencing microclimate variation in temperate fens relative to uplands and examined associated plant compositional gradients within fens. Large differences in average soil temperatures were observed between monitoring locations during a 161 day period in 2010 (range: 14.5 to 20.0 A degrees C). Using a regression approach, we developed accurate daily resolution soil temperature models (min and max) from a 29-sensor network by integrating atmospheric and hydrologic terms. Models accurately predicted validation observations from an independent 17-sensor network (R-2 values 0.92 minimums; 0.95 maximums) with low error compared to null models. Environmental variation in seasonal average soil temperature, snow depth, specific conductance, canopy closure, and non-vascular plant cover were correlated with spatial patterns in vascular plant community composition. Results of plant community analyses provided insufficient support to suggest boreal and non-boreal species occupied distinct microsites. Given the significant soil temperature variation observed, we suggest further investigation of climatic factors structuring wetland plant communities are warranted to inform the placement of conservation reserves that may be less vulnerable to climate change.