間伐等の手入れ・保育を適切に行っていない劣化・荒廃した森林では,森林の生物多様性がどのように低下しているかを明らかにすることを目的に野ネズミの捕獲調査を行った。林相の違いと,林相の境界との距離が野ネズミの生息にどのような影響を与えるかを明らかにするため,広葉樹二次林と人工針葉樹林の境界から針葉樹林帯の中心部へ向かって,広葉樹林から徐々に離れていくように距離を離して合計4プロット調査地を設け,シャーマントラップを各月196個設置し,累計トラップ数は1,176個となった。調査結果から,広葉樹林プロットにおいて捕獲された野ネズミは,全体の47.0%にあたる31頭で最も捕獲数が多かった。次いで,広葉樹林に隣接する針葉樹林プロットでのそれは全体の32.0%にあたる21頭であった。広葉樹林から遠い針葉樹林プロットでは野ネズミの生息数が少なかった。つまり,人工針葉樹林であっても広葉樹二次林に接し,その影響を受ける林縁部分においては野ネズミの利用が確認された。これは,人工針葉樹林でも今後適切な広葉樹林の配置を考慮すれば,生物多様性を増加させる可能性があることを示唆している。

How is forest biodiversity lost in the unmanaged forest that is not thinned and laid waste? The loss of biodiversity was investigated with wood mice for six months. In order to show how the habitation of wood mice is affected by the difference between forest types and distances from the boundary between the types, four investigation plots were prepared : The first plot was in the secondary broadleaf forest, not near the boundary. The second one was near the boundary and in the artificial coniferous forest. The third was between the boundary and the middle of the conifer forest. And the last plot was in the middle of the coniferous forest.196 Sherman traps were set every month and the total number of the traps came to 1,176. The results are as follows : In the first plot 31 mice were caught ; the number was equal to 47 percent of all the captured mice. In the second one 21 mice were caught ; the number was equal to 32 percent. In the fourth one few mice were caught. These results show that wood mice were found on the edge of the artificial coniferous forest that borders on the secondary broadleaf forest and is under the influence of it. This will suggest that forest biodiversity may be promoted even in the artificial coniferous forest if it is considered that the conifer forest is appropriately located next to the broadleaf forest.

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