Effects of Deer Grazing on Vegetation and Ground-Dwelling Insects in a Larch Forest in Okutama, Western Tokyo

الملخص EN

Sika deer (Cervus nippon) have experienced a rapid increase in the Japanese archipelago.

Although the effects of deer grazing have been widely studied, the indirect effects have received little attention.

Using an eight-year-old deer exclosure in western Tokyo (Japan), we studied the direct effects on plants and the indirect effects on insects and microenvironments.

Plant biomass was 14 times higher inside the exclosure than outside.

Shrubs (e.g., Aralia elata and Hydrangea paniculata) and trees (e.g., Symplocos sawafutagi and Clethra barbinervis) were more abundant inside, whereas only unpalatable trees in poor condition grew outside (e.g., Pterostyrax hispida and Cynanchum caudatum).

In the summer months, the maximum temperature was 8–10°C higher outside the exclosure and humidity was lower.

Soil movement was 80 times more pronounced outside than inside.

These results suggest that the abiotic environment became less stable for ground-dwelling insects.

Carabid beetles were less abundant outside than inside, suggesting that deer grazing reduced plants and subsequently lowered habitat quality for these beetles.

In contrast, carrion beetles, dung beetles, and camel crickets were more abundant outside.

The increase in these insects is attributed to the availability of deer feces and carcasses and is a direct effect of deer presence.