九州山地における落葉広葉樹二次林の発達に関する研究 : 階層構造と齢構成

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82年以前になんらかの攪乱があった後に成立したと推定される落葉広葉樹二次林の発達を階層構造，樹種構造，齢構成，直径成長等の面から解明した．この林分は階層構造的には明らかに高木層，亜高木層，低木層に区分することができた．樹木の年齢は高年齢域と低年齢域にそれぞれの分布の山が認められた．高木層を構成する樹木は高年齢域に集中していた．一方亜高木・低木層の樹木の年齢は個体により，また樹種によりかなりの差が認められたが，その分布の山は低い年齢域にあった．これは亜高木・低木層に比較的若い年齢で萌芽更新を行っている個体が多いことによると考えられた．直径順位の変動は高木層の構成木がかなり早い時期から上位を占めていることを示し，この林分はミズナラからクリヘ主林木が移行する過程にあったことを推測させた．In this paper, we have attemped to clarify the development of a deciduous broad-leaved forest from the viewpoint of stratification, age compostion and diameter growth. The forests surveyed were clearly stratified into three layers ; upper layer (h= tree height> 14m), mid layer (14>h>8m) and lower layer (h<8m). The upper layer was dominated by kuri (Castanea crenata S. et Z.) and mizunara (Quercus mongolica var. grosseserrata Rehd. et Wils.) trees, the mid layer by ryobu (Clethra barbinervis S. et Z.) and aohada (Ilex crenata Thunb.) trees, and the lower layer by shiromoji (Lindera triloba Bi.) trees. The low crown coverage of the upper layers caused the lower layer trees to increase in density and crown coverage. The ages of the upper layer trees, the mid layer trees and the lower layer trees were 62 Lo 82, 36 to 78 and 4 to 78 years, respectively. The initial appearaiice of individual trees was concentrated during a period about 80 years ago. From these findings, the surveyed forest has been identified as a secondary deciduous broad-leaved forest that had developed in the gaps or openings in the forest. The frequency distribution peaks for tree ages were found in both advanced and younger age groups. The peak in the younger age group is presumed to be closely related to young individuals of sprout origin. Judging from changes in diameter ranking, it was evident that kuri and mizunara trees ranked highly at an early stage in the development of the community and became stable in the higher ranks. Mizunara trees were dominant over kuri trees in diameter until recently, but now kuri trees seems to be dominant. Some of the mid and lower layer trees ranked highly at an early stage after gap formation. But with the development of the community, their rank has gradually shifted to the medium and subordinate class.

九州山地における落葉広葉樹二次林の発達に関する研究 : 階層構造と齢構成

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