Ambient and experimental warming effects on an alpine bryophyte community

Abstract

Alpine and Arctic bryophytes have been found to respond negatively to climate change, but as they are often analysed as one functional group, there is limited knowledge on species-specific responses. In this study, we examine how nearly two decades of experimental warming by open-top chambers and ambient warming have affected the bryophyte community structure in an alpine Dryas octopetala L. heath in Finse, southwest Norway. In contrast to what we expected, we found that bryophyte abundance, species richness, and evenness increased over time in the control plots, indicating a positive response to ambient warming. However, the increase in bryophyte abundance and cover was suppressed in experimentally warmed plots compared with control plots. Bryophyte community composition changed in a similar direction in response to both ambient and experimental warming. Acrocarpous mosses were not affected stronger by warming than pleurocarpous mosses, but individual species and taxa showed contrasting responses. Our study highlights the importance of studying bryophyte responses to environmental change, as well as combining long-term observations with experimental warming.