森林立地学会誌森林立地51（2），2009，117～125

森林立地学会誌森林立地51(2),2009,117～125

Jpn.J.For.Environment 51(2), 117-125 2009

Variation in tree mortality, recruitment, and mean turnover rates between topographic positions in a temperate coniferous forest

Yumiko Nakamori¹, Takeshi Torimaru², Daisuke Hoshino³

Shin-ichi Yamamoto⁴and Naoyuki Nishimura⁵
¹Forestry Experimental Station, Wakayama Prefecture Research Center of
Agriculture, Forestry and Fisheries,

　　　　　　　　　　²Faculty of Agriculture and Life Science, Hirosaki University

　　　　　　　　　　³Tohoku Research Center, Forestry and Forest Products Research Institute

　　　　　　　　　⁴Graduate School of Bioagricultural Sciences, Nagoya University

　　　　　　　　　　　⁵Faculty of Environment and Information Management, Nagoya Sangyo University

Forest community dynamics were investigated in relation to topography in two stands (Slope and Ridge stands) of an old-growth temperate mixed coniferous-broadleaved forest in the Sannoko Forest Reserve, south-western Japan. In 1985, all woody stems ＞5 cm diameter at breast height (DBH) in the plots were identified and marked; the census was repeated in 2002 and 2007. Over the census periods, mortality, recruitment, and mean turnover rates were higher in the Slope than the Ridge stand. The mortality rate in the understory layer was significantly higher in the Slope than the Ridge stand. Species’ mean turnover rate was significantly negatively correlated with mean DBH in the Slope but not the Ridge stand. Among the dominant species over the whole period, in both stands, a significant number of conifers died but little recruitment occurred, while broadleaved species populations appeared to be maintained at dynamic equilibriums. Species that dominated the Ridge stand did not exhibit a dynamic equilibrium, unlike those that preferred the Slope stand. The fact that populations of coniferous and ridge-abundant species were not in equilibrium suggests that regeneration properties in the seedling stages, which are linked to specific and infrequent events such as landslide disturbance and/or canopy gap formation, may be important in the maintenance of the population of each species.

Key words：demographic non-equilibrium, long-term study, old-growth, population characteristics, stand dynamics

中森由美子，鳥丸　猛，星野大介，山本進一，西村尚之：温帯針葉樹林における地形に関係した樹木の死亡率，加入率，平均，回転率．森林立地51:117-125,2009

奈良県吉野郡川上村にある原生状態の温帯針葉樹林における樹木群集動態の特徴を，異なった地形に成立した２林分の比較から明らかにするために，1985年に尾根調査区と斜面調査区において胸高直径（DBH）≧5cmの全木本幹の毎木調査を行い，2002年と2007年に再調査を行った。斜面林分の死亡率と新規加入率は尾根林分より高く，特に下層個体の死亡率は斜面林分で有意に高かった。主要樹種の個体群回転率は斜面林分ではDBHと負の相関があったが，尾根林分では小DBHサイズ樹種の低い個体群回転率により，そのような関係はみられなかった。主要樹種の個体群動態は調査期間に関係なく様々なパターンが確認されたが，斜面と尾根に共通して出現する種では，広葉樹では動的平衡状態の傾向，針葉樹では新規加入がなく個体数減少の傾向があった。また，個体群動態の動的平衡状態は，斜面で優占する種でみられたが，尾根で優占する種にはみられなかった。主要針葉樹と尾根で優占する種でみられた個体群動態の非平衡状態は，地すべり撹乱やギャップ形成などのまれなイベントに関係した実生段階の更新特性が，種個体群の維持に重要であることを示唆している。

キーワード：長期調査，動的非平衡，原生状態，個体群特性，林分動態