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

Abstract

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.

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

“…defecation, bedding and trampling), may perturb the forest understorey environment, e.g. by altering microclimate (Yamada & Takatsuki ), soil biotic and physical properties (e.g. Heckel et al .…”

“…defecation, bedding and trampling), may perturb the forest understorey environment, e.g. by altering microclimate (Yamada & Takatsuki 2015), soil biotic and physical properties (e.g. Heckel et al 2010;Bressette, Beck & Beauchamp 2012;Chips et al 2014;Shelton et al 2014), and the overall availability as well as spatial patterning of understorey light (Murray, Webster & Bump 2013) and soil resources (e.g.…”

Effects of an increase in population of sika deer on beetle communities in deciduous forests

“…These beetle groups were selected for several reasons. First, as these beetles inhabit the forest floor and are known to be sensitive to microclimatic changes (Rainio and Niemelä 2003, Arellano et al 2005), they are likely to sharply respond to the increase in the large herbivores (Rooney 2009, Yamada and Takatsuki 2015). Second, many beetles display species-specific ecological traits, which facilitates the investigation of the association between species life-history traits and their responses to large herbivore overabundance (Sumways 2007, Bachand et al 2014).…”

Appraisal of arid land status: a holistic assessment pertains to bio-physical indicators and ecosystem values

“…Thus, negative relationships of HCS with SQI suggest an increase in DUP at study sites. Yamada and Takatsuki (2015) have also correlated the impact of grazers and unpalatable species on forest productivity, and they concluded several patterns of direct and indirect effects of these variables on productivity at Larch forest in Okutama, Japan.…”