2018 Volume 8 Pages 17-32
We evaluated grazing effects of sika deer on various vegetation types and proposed some indicator species which can easily evaluate the effects in Kushiro-Shitsugen National Park. In the survey we recorded names of grazed plant species and counted the total number of grazed individuals in four vegetation types (bogs, fens, swamp forests and broad-leaved forests). For candidates of indicator species, we additionally measured grazing rate. Comparison of grazing rate among the vegetation types and negative relationship between grazing rate and flowering rate revealed that grazing effects are stronger in swamp forests and broad-leaved forests than in bogs and fens. This result suggests swamp forests and broad-leaved forests are suitable summer habitat for sika deer. Therefore, we need strong measures against intense grazing impact caused by deer to conserve the ecosystem of the park. The species which were abundant and showed the positive correlation between the total number of grazed individuals and grazing rate for candidates of indicator species were Persicaria thunbergii, Thalictrum spp. and Impatiens textorii. We propose they could be useful indicators to evaluate grazing effects of sika deer.