Do ungulates preferentially feed in forest gaps in European temperate forest?

Ungulate populations across Europe have been strongly increasing over the past decades. Simultaneously with this increase, concerns about the impact of ungulates on forest systems, and forestry specifically, are increasing. In this study we discuss how the common forestry practice of creating clear cuts in relatively homogenous, managed forests may increase the potential impact of ungulates. Growth of trees in full light conditions is generally higher, but due to higher photosynthetic activity they tend to have higher C:N ratio in their leaves thus decreasing food quality. Next to that, biomass of herbaceous vegetation is enhanced in clear cuts. These changes likely affect foraging decisions of ungulates and it has been suggested that ungulates forage in forest gaps rather than in closed forest. We tested this hypothesis by using an experimental approach. The experiment was conducted in the Bialowieza Primeval Forest in Poland, where a full assemblage of native large herbivores occurs. Six plots (6 m x 6 m) inside small clear cuts were compared to six control plots in adjacent closed forest. To exclude the effect of differences in number and species composition of available tree saplings, equal numbers of trees saplings of five species were planted at each plot. Ungulate visitation frequency and visitation time were measured by means of three methods: track plots, camera-and video trapping, and pellet counts. Visitation frequency of all ungulates combined (European bison, red deer, roe deer, moose and wild boar) was almost twice as high inside forest gaps compared to closed forest. Also cumulative visitation time by all ungulates tended to be higher inside forest gaps. Red deer showed the strongest preference for gaps, and duration of single visits was almost seven times longer for forest gaps than in closed forest. The observed preferential foraging of ungulates in forest gaps leads to an uneven distribution of their browsing behaviour. Hence, the creation of forest gaps by clear cutting followed by reforestation provides attractive foraging patches for ungulates potentially leading to high damage. In this way, forestry practices may enhance damage of ungulates to plantations especially when due to management the surrounding forest has a low carrying capacity for ungulates. We suggest that there is much to gain if management approaches would focus at influencing foraging behaviour of ungulates and reduce their concentration in forest gaps, rather than purely focusing on population control. (C) 2009 Elsevier B.V. All rights reserved.