Vegetation changes at oligotrophic grasslands managed for a declining butterfly

A selection of sites occupied by the EU-protected marsh fritillary (Euphydryas aurinia) in western Czech Re-public were subjected to a vegetation survey 15 years ago and again recently. In the 66 time-replicated 25 m2 plots from 12 sites, representing the diversity of E. aurinia-occupied oligotrophic grasslands in the Slavko-vskATIN SMALL LETTER Y WITH ACUTE les Protected Landscape Area (and covering a fifth of the currently-occupied Czech sites), we recorded quantitative representation of vascular plants and mosses. We analysed the data using multivariate ordina-tions, asking how the vegetation changed between the surveys, how was it affected by the conservation man-agement applied and how it affected occupancy by the butterfly larval nests; the vegetation patterns were interpreted using Ellenberg's plant indicator values. Between the two surveys, the overall representation of the larval host plant, Succisa pratensis, did not change; tree and herbs layers (both grasses and forbs) in-creased and the moss layer decreased. Across surveys, the main driver of vascular plants' species composition was moisture, followed by soil reaction and nitrogen, whereas in mosses, nitrogen was the main factor. The main change between the surveys was the increase of nitrogen accompanied by decreased light, probably due to increase of competitively strong plants. Butterfly occupancy declined at sites with high soil moisture and increased at sites with higher soil reaction. Mowing of moist nitrogen-rich sites, but not drier nitrogen-poor sites, increased occupancy, illustrating the need for context-dependent interventions. All the evidence thus shows that E. aurinia prefers drier, warmer and less acidic conditions within the generally moist acidic grasslands and that ongoing eutrophication represents a potential problem in the future.

Automated summary

A study was conducted on the vegetation of EU-protected marsh fritillary habitats in western Czech Republic. The study found that the larval host plant remained stable, but there was an increase in tree and herb layers and a decrease in the moss layer. The main factors influencing the composition of vascular plants were moisture, soil reaction, and nitrogen, while nitrogen was the main factor for mosses. Butterfly occupancy decreased in sites with high soil moisture and increased in sites with higher soil reaction.