Spatial interactions between ungulate herbivory and forest management

The SE-Veluwe is a forested area in The Netherlands consisting mainly of Pinus and heathlands and includes mono- and mixed species stands of Fagus sylvatica, Quercus robur, Q. petraea, Picea abies, Pseudotsuga menziesii, Betula pubescens and B. pendens. In this area, forest managers differ in management targets. Managers with a productivity-oriented target feel limited in meeting their target because neighbouring managers with biodiversity as main target do not or insufficiently control ungulate levels. The objective of this study was to assess to what extent ungulate herbivores affect natural regeneration and to gain insight in the spatial interactions between ungulate grazing, forest management and natural regeneration. This was assessed using the model FORSPACE, which is a process-based and spatial-explicit simulation model that integrates the impacts of ungulate grazing (cattle, horse, red deer, fallow deer, roe deer and wild boar) and forest management.We found that spatial interactions caused important local differences including: (i) spatial effects due to forest management; (ii) spatial interactions between ungulate species; (iii) spatial effects due to the distribution of seed sources of trees; and (iv) spatial interactions between plant species and grazing intensity. In general, we conclude that the effects of forest management on regeneration of trees are much more profound than that of ungulate grazing and browsing. Moreover, there are relatively small differences in the effects of the ungulates at very low to very high densities.