Sensitivity of stand dynamics to grazing in mixed Pinus sylvestris and Quercus pubescens forests: A modelling study

By comparing simulated with empirical data, it was evident that the model underestimated Scots pine basal area if succession was simulated without goat grazing. Introducing grazing led to a more realistic, higher abundance of Scots pine in the model. Regeneration of the more browsing-susceptible pubescent oak was seriously suppressed during the simulated intense grazing period, which led to a higher occurrence of Scots pine in the model. Although after 400 years of simulated succession pubescent oak reached nearly the same basal area as without historic intensive grazing, succession was delayed. The model application suggests that goat grazing allows for a much longer period of codominance of Scots pine and pubescent oak in these forests. The changes in the simulated successional pathways support the view expressed in other studies that human impacts may alter forest succession substantially. Our results allow for a first qualitative estimate, and they make clear that the representation of browsing in forest succession models needs to be improved further.