Ungulates increase forest plant species richness to the benefit of non-forest specialists.

Glob Chang Biol. 2018 Feb;24(2):e485-e495. doi: 10.1111/gcb.13899. Epub 2017 Oct 11. Boulanger V1, Dupouey JL2, Archaux F3, Badeau V2, Baltzinger C3, Chevalier R3, Corcket E4, Dumas Y3, Forgeard F5, Mårell A3, Montpied P2, Paillet Y3, Picard JF2, Saïd S6, Ulrich E1. Author information 1 Office National des Forêts, Département Recherche, Développement et Innovation, Fontainebleau, France. 2 INRA - Université de Lorraine, UMR 1137 Ecologie et Ecophysiologie Forestières, Champenoux, France. 3 Irstea, UR EFNO, Domaine des Barres, Nogent-sur-Vernisson, France. 4 Université de Bordeaux, UMR1202 BioGeCo, Allée Geoffroy St-Hilaire, Pessac Cedex, France. 5 Laboratoire d'Ecologie Végétale, Université de Rennes I, Rennes Cedex, France. 6 Office National de la Chasse et de la Faune sauvage, DRE Unité, Ongulés sauvages, Birieux, France. Abstract Large wild ungulates are a major biotic factor shaping plant communities. They influence species abundance and occurrence directly by herbivory and plant dispersal, or indirectly by modifying plant-plant interactions and through soil disturbance. In forest ecosystems, researchers' attention has been mainly focused on deer overabundance. Far less is known about the effects on understory plant dynamics and diversity of wild ungulates where their abundance is maintained at lower levels to mitigate impacts on tree regeneration. We used vegetation data collected over 10 years on 82 pairs of exclosure (excluding ungulates) and control plots located in a nation-wide forest monitoring network (Renecofor). We report the effects of ungulate exclusion on (i) plant species richness and ecological characteristics, (ii) and cover percentage of herbaceous and shrub layers. We also analyzed the response of these variables along gradients of ungulate abundance, based on hunting statistics, for wild boar (Sus scrofa), red deer (Cervus elaphus) and roe deer (Capreolus capreolus). Outside the exclosures, forest ungulates maintained higher species richness in the herbaceous layer (+15%), while the shrub layer was 17% less rich, and the plant communities became more light-demanding. Inside the exclosures, shrub cover increased, often to the benefit of bramble (Rubus fruticosus agg.). Ungulates tend to favour ruderal, hemerobic, epizoochorous and non-forest species. Among plots, the magnitude of vegetation changes was proportional to deer abundance. We conclude that ungulates, through the control of the shrub layer, indirectly increase herbaceous plant species richness by increasing light reaching the ground. However, this increase is detrimental to the peculiarity of forest plant communities and contributes to a landscape-level biotic homogenization. Even at population density levels considered to be harmless for overall plant species richness, ungulates remain a conservation issue for plant community composition. KEYWORDS: biodiversity; biotic homogenization; exclosure; large herbivores; species richness; temperate forest; vegetation cover; vegetation monitoring Comment in Are ungulates in forests concerns or key species for conservation and biodiversity? Reply to Boulanger et al. (DOI: 10.1111/gcb.13899). [Glob Chang Biol. 2018] The role of ungulates in nowadays temperate forests. A response to Fløjgaard et al. (DOI:10.1111/gcb.14029). [Glob Chang Biol. 2018]