Grazing by wild red deer maintains characteristic vegetation of semi-natural open habitats: Evidence from a three-year exclusion experiment
By Friederike Riesch, Bettina Tonn, Hans Georg Stroh, Marcus Meißner, Niko Balkenhol & Johannes Isselstein
Many plant and animal species in Europe depend on the semi-natural open landscapes created by the extensive land use practices of farmers in the past centuries. Maintaining these habitats today is challenging because most of the agricultural land in Europe is intensively farmed, and areas, where farming is unprofitable, are increasingly abandoned. To counteract the ongoing loss of semi-natural open habitats and their inhabiting species, conservation management has to compensate for the decline of traditional agricultural land use practices.
Extensive livestock grazing, for instance, has become a valuable tool for conservation management. Large herbivores such as cattle or sheep can benefit vegetation structure and composition and contribute to biodiversity. Areas of high conservation interest that are too large or inaccessible, however, cannot be grazed by livestock. However, what about wild ungulates – could these free-ranging herbivores also help to preserve characteristic open habitat plant communities?
To answer this question, we conducted an experiment in the actively used Grafenwöhr military training area in south-eastern Germany. This area, totalling 230 km2, is to a great extent protected, and 40% are covered by open landscape. A large population of wild red deer uses the different open habitats for foraging throughout day and year.
To study the effect of red deer on the vegetation, we installed 15 and eight exclusion fences (11 m × 11 m) in lowland hay meadows and European dry heaths, respectively. For three years starting in 2015, we measured the height of vegetation and litter, estimated the cover of bare soil and the biomass contribution of common heather and counted individuals of woody species. Furthermore, we compared the plant diversity and composition before (in 2014) and after our experimental period (2018).
After three years of fencing, the grassland plant communities were less diverse compared to open plots. In both grasslands and heathlands, the plant composition changed and the height of vegetation and litter increased in response to red deer exclusion. Additionally, inside heathland fences, the cover of bare soil decreased, while the number of woody plant individuals increased. The communities of fenced plots hence showed characteristics of more closed vegetation – the beginning of a development that might end up in shrub or forest. Accordingly, the conservation value of the studied open habitat types decreased when red deer were excluded.
Apart from the general effect of red deer grazing on the vegetation, we investigated how to influence the intensity of red deer grazing. This could be important for conservation management because grazing requirements differ between habitat types. Red deer favour the fresh vegetation regrowing after biomass removal, e.g. burning or mowing. Consequently, our 15 paired plots in grasslands were equally allocated to annually burnt, mown or untreated grasslands. Our results showed that open and fenced plots differed most strongly in mown grasslands. Camera traps provided evidence that red deer used these areas most intensively. Thus, it seems possible to influence the habitat use of red deer by mowing selected areas.
Overall, we conclude that grazing by red deer is beneficial in different semi-natural open habitats. Accordingly, we suggest wildlife grazing as an alternative conservation management option, particularly suitable for large areas of conservation interest with limited accessibility.
The project was supported by funds of German government’s Special Purpose Fund held at Landwirtschaftliche Rentenbank [28 RZ 7007].
This is a plain language summary for the paper of Riesch et al. published in Applied Vegetation Science (https://doi.org/10.1111/avsc.12505). The post was prepared by Friederike Riesch and Bettina Tonn.
