Abundant artificial grasslands around forests increase the deer impact on forest vegetation

Abstract

Recent research suggests that deer impact on forest vegetation differs according to the surrounding landscape composition. However, there is no consistent trend on how food-rich habitat affects deer browsing impact on forest vegetation. The study took place in Yatsugatake region (Japan) where forests dominate, there are many artificial grasslands with various size, and large crop fields exist around urban area. We examined whether (1) the surrounding abundant alternative food (in this study, artificial grasslands) in forests increases deer density and (2) the high deer density affects forest vegetation more seriously. We evaluated the coverage of understory vegetation and the occurrence of debarking on standing trees. This study demonstrated that the abundant surrounding artificial grasslands increased deer density in forests. High deer density impacted forest vegetation negatively. Pellet group number was significantly higher in forests with high percentage of artificial grassland area and low percentage of crop field area. It was also higher in evergreen forests compared with other forest types. The coverage of understory vegetation was significantly reduced on the plots where many pellet groups were found. The occurrence of debarking on standing trees was significantly higher on the plots where many pellet groups were found than on plots with less pellets. In conclusion, abundance food-rich habitat around forests increases deer density in forests, which leads to a stronger impact of deer on forest vegetation.