Effects of Strip-cutting on Stand Floor Micro Climate and Tree-species Diversity in a Japanese Cypress Plantation

27 Mar Effects of Strip-cutting on Stand Floor Micro Climate and Tree-species Diversity in a Japanese Cypress Plantation

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Abstract

21年生ヒノキ同齢林を対象として帯状伐採を行い, 伐採が林床の微気象因子と植生に及ぼす影響について伐採直後から15カ月間の調査を行った。林床の相対光強度は, 伐採前の0.15から伐採部中央で0.6, 林縁で0.3程度まで上昇した。林床の気温, 飽差, 地温および土壌含水率のうち, 伐採部と林縁における地温の変化が著しかった。伐採直後と15カ月後の樹木種の個体数と被覆面積の測定より, 林床植生の多様度指数 (H´) を算出した。伐採部のH´は伐採直後が最低であり, 15カ月後には林内と同じ程度にまで回復した。林縁部のH´は調査期間を通して高い値であり, 加えて林内においてもH´は上昇していた。帯状伐採は, 新たに形成される伐採面と林縁部の広さに特徴があり, 林床の微気象や植生への影響を通じ, ヒノキ人工林の生物多様性の維持に有効と考えられた。

English Abstract

In a 21 years even-aged Japanese cypress plantation, we conducted investigation about the strip-cutting influences to the stand floor micro climates and vegetations for 15 months from cutting. The relative light intensity in the stand floor rose from 0.15 to about 0.3 in stand edge, and nearby 0.6 at the center of cutting area. Among the air temperature, air vapor pressure, soil temperature, and the soil water content in stand floor, soil temperature showed the most remarkable change at cutting area and stand edge. The diversity index (H´) of stand floor vegetation was calculated from the population of sapling and area coverage. Immediately after cutting, H´ of cutting area showed the minimum value. However, 15 months after, it was recovered even to the same grade as the stand interior. Through the investigation term, H´ of stand edge was still maintain high value, and in addition, H´ was rose in the stand interior. Strip-cutting has the feature in the broadly cutting area and edges, micro climate and the vegetation influences in the stand floor. These results were considered to be effective in the mainte nce of the biodiversity on the Japanese cypress plantation.