Successional changes on a former tank range in eastern Germany: Does increase of the native grass species Molinia caerulea cause decline of less competitive Drosera species?

Abstract

Summary Invasion of natural ecosystems by weedy grasses is often associated with increasing levels of disturbance. However, there is substantial evidence that cessation of disturbance can also lead to plant invasions. This paper explores vegetation development on a former military training area in eastern Germany. Many military training areas have a high nature conservation value as they offer large un-fragmented areas and valuable open landscapes. In eastern Germany, 4.4% of the land is covered by military training facilities. Following German reunification in 1990 large tracts of land that had been used for military training purposes were converted to civil use. Cessation of military activity is leading to a decline of open habitats through natural succession. The study investigates whether succession is accompanied by a spread of dominant species, e.g. Purple moor grass (Molinia caerulea L. Moench) and whether this process results in a decline of pioneer species (e.g., Drosera species). As a potential management option we explored grazing by moose (Alces alces L.) and other wild animals. The current state of the vegetation and its development was investigated at landscape and species levels. The influence of animals was documented by determining the type of ground disturbance and the impact on the herbaceous vegetation. The trajectory of succession involves the increase of species with high competitive abilities, particularly Molinia caerulea, and a decline of less competitive Drosera species. The pattern of development of the vegetation suggests that the Drosera species will soon survive in only a few locations. Wild animals exerted a significant influence on the vegetation, with most disturbances being the result of trampling. Tracks left by animals can provide regeneration niches for the Drosera species. However to guarantee the maintenance of large open habitats other management practices such as sod cutting are required.