Unveiling Plant Community Shifts as a Consequence of Climate Change

Abstract

<p>Coastal wetlands are considered valuable ecosystems for their biodiversity and the wide range of ecosystem services they supply. However, coastal wetlands worldwide are also subject to various impacts resulting from natural and anthropogenic drivers, such as urbanization and residential developments, conversion to agricultural land and climate change related impacts such as sea level rise, changes in precipitation, inundation, changes in salinity and erosion. The consequences of climate change over recent decades are evident in the Baltic Sea region, with modifications in sea water circulation, temperature and salinity. Due to the high importance of coastal wetlands and the impacts of climate change on this ecosystem, it is essential to determine how future conditions will influence coastal plant community functioning. In the Baltic Sea, both salinity and water levels have been shown to have a strong influence on coastal plant community composition. In order to assess the effects of climate change in coastal wetlands, an investigation of the influence of changes in water level and salinity on coastal wetland plant communities was undertaken. Future scenarios of Baltic coastal wetlands were evaluated using a three-year mesocosm experiment simulating altered environmental conditions. The response of three plant communities (Open Pioneer-OP, Lower Shore-LS and Upper Shore-US) were assessed in terms of changes in species composition over time. The experiment included 45 mesocosms, 15 per community with 5 treatments (3 replicates per treatment) with control, altered water level and salinity. In order to analyse the differences among treatments in plant communities through time, Permutational Multivariate analysis of variance (PERMANOVA) and species contribution were performed. Bray-Curtis dissimilarity was calculated from species importance values. Finally, a principal coordinate analysis (PCoA) based on Bray-Curtis dissimilarity was used to visualize the responses of the communities to treatments in each year. The results showed that all factors, year and treatment, influenced plant community composition. PCoA revealed plant community shifts in OP in the second year of experiment. Species were more clustered in LS and US communities compared to OP, but changes were still noted. The small spread of species throughout the years in ordination space in LS and US suggests a higher degree of similarity between communities across treatments. Based on these mesocosm experiments, it can be concluded that altered water level and salinity in Baltic coastal wetlands can have important consequences for species composition in plant communities, which support high diversity and are important for conservation.</p>