研究内容要約
Research
Summary |
御岳山地域におけるシカの生息状況と、シカによるレンゲショウマの採食状況を明らかにすることを目的とし、野外調査を行った。
表参道や日の出山、ロックガーデン等、多くの場所で個体目撃やフィールドサイン(糞や植物採食の跡等)が確認されたことから、広範囲にわたりシカが生息していると考えられる。2016年では昼間の時間帯にもシカが確認された。センサーカメラ調査では、富士峰園地、長尾平、神苑の森においてほとんどの月で確認された。
富士峰園地における植生調査では76種の草本と木本で採食痕がみられた。その中には希少種であるレンゲショウマ、カタクリ、タカオヒゴタイが含まれていた。
御岳山域におけるレンゲショウマの生息状況とシカによる採食状況を把握するためにコドラート調査を行った。被食個体密度や被食率が高い調査区も見られた。特に5月にシカよる採食圧が高くなることが分かり、5月以降に個体サイズが小さくなる調査区も見られた。富士峰園地では防獣柵設置前よりも柵設置後に個体密度が高くなった。シカの採食圧が無くなり、個体密度が高くなったことが推測される。
また開花個体や種子を生産した個体が少ない調査区や小型の個体が多くを占める調査区も見られた。このような小さな個体群に対してはシカによる採食圧は脅威になると考えられる。
We conducted a field survey aimed at ascertaining the habitat status of Sika deer in the Mount Mitake region and the extent to which those deer feed on Anemonopsis macrophylla (commonly known as false anemone).
Deer sightings and field signs (feces and signs of browsing on plants) in many locations, including the main approach to the shrine, Mount Hinode, and the Rock Garden suggest the presence of deer across an extensive area. Deer were also observed during daylight hours in 2016. In a survey conducted using sensor cameras, deer were observed almost every month in Fujimine Garden, Nagaodaira, and the shrine grove.
A survey of vegetation in Fujimine Garden found that 76 varieties of herbaceous and woody plants showed signs of deer browsing. Among those varieties were the rare species Anemonopsis macrophylla, Erythronium japonicum (commonly known as dogtooth lily), and Saussurea sinuatoides (a thistle-like plant known as Takao-higotai in Japanese).
We conducted a quadrat survey to ascertain the habitat status of Anemonopsis macrophylla in the Mount Mitake region and the extent to which deer feed on this species. Some sample plots had a high density of browsed plants and a high predation rate. We discovered that deer browsing pressure is particularly high in May and in some sample plots, the size of specimens declines from May onward. In Fujimine Garden, specimen density was higher after the installation of an anti-predator fence than it had been before. It is presumed that this is because deer browsing pressure disappeared and specimen density increased.
We also found sample plots with few specimens in flower and few that had produced seeds, and sample plots where the majority of specimens were small. Deer browsing pressure is believed to be a threat to these populations of small specimens.
|
