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森林がどのように成立し、現在の林分の発達に影響したのかが公園管理をする上で重要である。調査地を撹乱のスケールによって景観レベルと林分レベルの二つに分け、本研究では林分レベルで撹乱体制と森林動態を明らかにすることを目的とした。標高600～1100mの地域に15 プロットを設置し、DBH 3 cm以上の全樹種を毎木調査し、コア採取して年輪解析をした。全プロットで29 種が出現し、ブナのBA 優占度に基づき発達段階ごとにプロットを分類した。DBH階別本数頻度分布は、発達段階によって違いがあったが、相関係数、D-H拡張相対成長式のパラメータは発達段階による違いはなく、種数、均等度、多様性も発達段階による違いはみられなかった。個体の肥大成長量、DBH 階別本数頻度分布、樹幹部萌芽率から、撹乱体制を明らかにした結果、プロットごとに頻度、強度、時期の異なる伐採が行われたと推定された。景観レベルで人為的撹乱が及んでいないと思われた林分も、林分レベルでみるとその多くは様々な規模、強度、時期の撹乱を受けていた。それによってブナ－ミズナラ群落、クリ－ミズナラ群落などの代償植生に置き換わっており、人為的撹乱によって景観レベルでもブナ林の再生複合体として異なるphase を形成していると考えられる。国立公園の森林植生を管理するためには、森林を動的なものと認識し、森林の撹乱パターンを明らかにすることで、様々なスケールでより長期的にモニタリングすることが必要である。 / The purpose of this study is to clarify the forest dynamics and disturbance history at two levels (the landscape level and the forest level).This study focused on the forest level how human-related processes had an influence on the forest dynamics that are important to environmental management in the Daisen national park area. For the forest level analysis, we set 15 plots at the areas where natural vegetation was beech forest (600 to 1100m above sea level). Within the fifteen plots, total 0.45 ha, twenty-nine species (DBH>=3 cm) were found. We analyzed the tree-ring widths and classified the plots as Early, Middle and Late stages of forest development by BA dominance of Fagus crenata. The DBH frequency distribution by the number of trees was different from each stages of forest development. The DBH?height relationship was not fitted to the hyperbolic equation (1/H=1/AD^h+1/H^*) by each stages of forest development. There were not cleary correlation about number of species, homogeneity factor and species diversity (H') which were calculated on the basal area of each species, by each stages of forest development. It is estimated from the percentage of growth change (%GC) that forest cut down with different frequency, intensity, and times had been carried out in every plots. Many forests were thought that there was no influence of human disturbances at landscape level. However, they were affected by human disturbances with different frequency, intensitiy and time at forest level. Natural vegetation is Lindeto umbellatae-Fagetum crenatae in the Daisen national park area. It was changed into Fagetum crenatae-Quercetum crispulae, Castaneo-Quercetum cripulae. Actual vegetation is the different phases of the regeneration complex in natural beech forests at landscape level. We should recognize the forest to be dynamic to manage the forest vegetation in the national park, and it is important that we clarify the disturbance patterns in the forest ecosystems. It is necessary to manage the processes in the regeneration complex of forests in various scales, and to monitor them in a long-term. |
