Abstract
Mires are characterized by plant communities of high conservation and societal value, which have experienced a major decline in area in many parts of the world, particularly Europe. Evidence suggests that they may be particularly vulnerable to changes in climate and nutrient addition. Although they have been the focus of extensive paleoecological research, few attempts have been made to examine the dynamics of mire vegetation during the current era of anthropogenic environmental change.To assess long‐term change in the spatial structure and composition of a lowland mire community, in 2016 we resurveyed plots first surveyed in 1951. Measures of species richness and composition were compared between the two surveys, and changes in community composition were related to plant traits.Overall, mean species richness declined by 26%. The area of occupancy declined in 37% of species, which were primarily oligotrophic species typical of nutrient‐poor bog communities. Conversely, occupancy increased in 21% of species, especially those that were more tolerant of higher nutrient availability. These changes were associated with variation in plant functional traits, as indicated by an increase mean Ellenberg trait values for nitrogen and mean temperature, and a decline in values for precipitation. These results suggest that eutrophication and climate change have been key drivers of floristic change on this site. Synthesis. This investigation provides a rare assessment of the dynamics of a mire community over a multi‐decadal interval. Results indicate that substantial change has occurred in the composition of the community, and the distribution of species within it. The investigation provides evidence of the impact of environmental change on the composition and structure of a lowland mire community, and highlights challenges for its future conservation.
Highlights
Mires are wetland ecosystems characterized by the active accumulation of organic matter and are globally recognized as being important for biodiversity conservation, climate regulation, and human welfare (Parish et al, 2008)
| 13917 species, indicating shifts in spatial distribution (Table 1, Figures S3 and S4). Four species increased their area of occupancy since 1951, namely P. aquilinum, Sphagnum cuspidatum, Sphagnum subnitens, and P. sylvestris
Significant declines in the area of occupancy were observed in seven species, namely Trichophorum germanicum, R. alba, Carex rostrata, Cirsium dissectum, Sphagnum compactum, Rhynchospora fusca, and Lycopodiella inundata
Summary
Mires are wetland ecosystems characterized by the active accumulation of organic matter (peat) and are globally recognized as being important for biodiversity conservation, climate regulation, and human welfare (Parish et al, 2008). Previous research into the long-term changes in plant communities in the neighboring county of Dorset has highlighted eutrophication and climate change as key drivers of vegetation change during the past 70 years (Diaz et al, 2013; Keith et al, 2009, 2011; Newton et al, 2012) On this basis, we hypothesized that the composition of plant communities in Cranes Moor would have been influenced by these factors, leading to a decline in species associated with low nutrient status, and those susceptible to summer drought. Records were made by surveying 50 randomly distributed 25 × 25 cm quadrats in each of these vegetation plots (Figures S1 and S2)
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