Global Ecology and Conservation (Aug 2023)
Long-term data indicates positive effects of habitat size and ambiguous climate effects on population growth of the endangered wetland orchid Dactylorhiza majalis
Abstract
Central European semi-natural wet grasslands are known for their high nature value and diversity of rare and endangered species. However, they are experiencing deteriorating habitat quality and species losses, a problem that may aggravate with climate change. Identifying key factors that jeopardize wet grassland species is an urgent task for effective conservation. To this aim, we studied the endangered orchid Dactylorhiza majalis, a characteristic species for Central European wet grasslands of high biodiversity and habitat quality. We compiled long-term monitoring data (1993 – 2020) for 84 populations located within the species’ range center (NE-Germany) and analyzed i) long-term trends in population size and ii) immediate and time-lagged effects of six climatic variables and habitat size on population growth. Situated mostly within nature reserves, the majority of populations remained stable (51%) or increased (31%) in population sizes. However, 18% declined despite suitable habitat management. Small habitat size negatively affected population growth. The effect of climatic variables on population growth was rather small and ambiguous, while asynchronous variation among populations was strong. Population growth increased with higher spring temperatures but decreased with lower spring precipitation; lower spring precipitation and late frost events had positive time-lagged effects in the next season. We conclude that D. majalis may withstand moderate levels of climate change, provided that future conservation practice can ensure suitable management and water tables sufficiently high for wet grassland species. Our results highlight the vulnerability of small wet grasslands and that large habitat size promotes effective conservation of one of the most diverse semi-natural habitats in Central Europe.
