森林立地学会誌 森林立地48(2), 2006, 91〜98
Jpn.J.For.Environment 48(2), 91−98 2006
大台ヶ原においてニホンジカとミヤコザサが表層土壌の温度・水分状態に及ぼす影響
古澤仁美＊・日野輝明＊＊・金子真司＊・荒木 誠＊
＊森林総合研究所・＊＊森林総合研究所関西支所
ニホンジカによる林床のミヤコザサの採食と人為的なササ刈りが表層土壌の温度・水分状態に及ぼす影響を明らかにするため，大台ヶ原の針広混交林において，シカ排除処理とササ刈り処理の有無を組み合わせた４つの処理区で，処理開始から３〜４年後の表層土壌の水分ポテンシャルと地温を測定した。すべての処理区とも表層土壌のマトリック・ポテンシャルは大半が−4〜0 kPaの範囲と湿潤状態であったが，シカ排除・非ササ刈り区では−4 kPa 以下の出現頻度が他の処理区より高く，やや乾く傾向が認められた。表層土壌の月平均地温は，シカ排除・非ササ刈り区では対照区に比べて夏季には1〜2℃低く，冬季は逆に1〜2℃高い傾向が認められた。シカ排除処理・非ササ刈り区では，ササの地上部現存量が増加したことに伴って，ササによる被覆効果や蒸散量の増大が土壌水分や地温に影響を与えたことが示唆された。ただし，処理区間の土壌水分と地温の違いは，土壌の生物化学的プロセスに明確な影響を与えないと推察された。したがって，ミヤコザサの地上部現存量の増加や減少が本研究の測定値内で生じても，温度，水分環境の面からこの森林の養分循環に影響を及ぼす可能性は小さいと考えられた。
Hitomi Furusawa, Teruaki
Hino, Shinji Kaneko and Makoto Araki : Effects of sika deer (Cervus nippon)
and Sasa nipponica on the temperature and moisture of the surface soil
on Mt. Ohdaigahara
We examined the effects of Sasa (Sasa
nipponica, a dwarf bamboo) grazed by deer (Cervus nippon) or removed
artificially on the temperature and moisture regime of the surface soil in a
temperate mixed forest at Ohdaigahara, in southern Honshu, using four types of
experimental plot, and involving combinations of deer (excluded or present) and
Sasa (removed or intact). More than half of the observed values of the matric
potential of the surface soil ranged between –4 and 0 kPa in all treatment
plots, although the soil moisture tended to be less humid in the
deer-excluded/Sasa-intact plot than in the other plots. The monthly mean soil
temperature in the deer-excluded/Sasa-intact plot was 1-2 degrees lower than
that in the control plot in summer, and 1-2 degrees higher than that in the
control plot in winter. These results suggest that the increase in the
aboveground biomass of Sasa in the deer-excluded/Sasa-intact plot induces
changes in soil temperature and moisture by increasing the cover and
transpiration by the Sasa. However, the differences in the environmental
changes between the plots were small and unlikely to have significant effects
on litter decomposition and N mineralization in the soil. As a result, the
observed change in the aboveground biomass of Sasa does not seem likely to
influence the nutrient cycle in this forest by changing the temperature and
moisture of the surface soil.