Recent changes in the plant composition of wetlands in the Jura Mountains

Abstract

Aim: To assess vegetation changes in montane fens and wet meadows and their causes over 38 years. Location: Wetlands, Jura Mountains (Switzerland and France).Methods: Plots were inventoried in 1974 and re-located in 2012 (quasi-permanent plots) on the basis of sketches to assess changes in plant communities. The 110 plots belonged to five phytosociological alliances, two in oligotrophic fens (Caricion davallianae, Caricion fuscae) and three in wet meadows (Calthion, Molinion, Filipendulion).Changes between surveys were assessed with NMDS, and changes in species richness, Simpson diversity, species cover and frequency and the causes of these changes were evaluated by comparing ecological indicator values. Results: Changes in species composition varied between alliances, with a generaltrend towards more nutrient-rich flora with less light at ground level. Species diversity declined, with a marked decreasing trend for the typical species of each alliance. These species were partly replaced by species belonging to nitrophilous and mesophilous grasslands. However, no trend towards drier conditions was detected in these wetlands. The largest changes, with an important colonization by nitrophilous species, occurred in the Swiss sites, where grazing was banned 25 years ago. As a result of floral shifts, many plots previously belonging to fens or wet mesotrophic meadows shifted to an alliance of the wet meadows, generally Filipendulion. Moreover, communities showed a slight trend towards more thermophilous flora. Conclusions:The investigated wetlands in the Jura Mountains have suffered mainly from eutrophication due to land-use abandonment and N deposition, with a loss of typical species. Areas with constant land use (grazing or mowing) showed less marked changes in species composition. The most important action to conserve these wetlands is to maintain or reintroduce the traditional practices of extensive mowing and livestock grazing in the wetlands, especially in areas where they were abandoned 25 years ago. This previous land-use change was intended to improve fen conservation, but it was obviously the wrong measure for conservation purposes. K E Y W O R D S ecological indicator values, eutrophication, fens, grazing, land-use changes, N deposition, re-survey, semi-permanent plots, wet meadows Nomenclature: Aeschimann et al. (2005) for vascular plants; Delarze et al. (2015) for plant communities Applied Vegetation Science RION et al.

Niche differentiation, competition or habitat filtering? Mechanisms explaining co‐occurrence of plant species on wet meadows of high conservation value

“…Therefore, we regarded species typical of mesic meadows (belonging to the Arrhenatherion alliance) as indicators of drainage combined with too frequent and intensive, mechanical mowing (practised more than two times per year) (Ziaja et al, 2017). Species typical of wet, Calthion meadows we recognised as indicators of a combination of episodic flooding, fertilisation, and moderate mowing (practised one to two times per year; Ratyńska et al, 2010), whereas hygrophilous tall herbs (Filipendulion) as indicators of either high nitrogen content in the soil, corresponding to high biomass production (Blackstock et al, 1998), or secondary succession of vegetation due to the cessation of mowing (Rion et al, 2016). The nomenclature of vascular plants followed Euro+Med (2006).…”

Declines in occurrence of plants characteristic for a nutrient‐poor meadow habitat are partly explained by their responses to nutrient addition and competition

“…Although there are no data on the degree of nutrient enrichment of the Molinia meadows around Lower Lake Constance, increasing dominance of species typical for nutrient-rich habitats was documented in similar plant communities in calcareous fens (Caricion davallianae) in Switzerland in recent decades (Bergamini et al, 2009;Moradi et al, 2012;Rion et al, 2018). Indeed, many species have declined in the Molinia meadows around Lower Lake Constance (Peintinger, 2012).…”

Pasture management, grazing, and fire interact to determine wetland provisioning in a subtropical agroecosystem

“…Fertilizer application is another agricultural management practice with critical impacts on wetlands. The use of fertilizers can increase nutrient runoff, driving eutrophication of previously oligotrophic wetlands (Navr atilov a et al 2017, Rion et al 2018. Eutrophication in turn may decrease species diversity, increase biodegradability of dissolved organic carbon (Mao et al 2017), and increase decomposition through changes in litter quality, thus accelerating nutrient cycling.…”