Occurrence pattern of Thujopsis dolabrata saplings in the understory of an old-growth Chamaecyparis forest, Akasawa Forest Reserve, Central Japan
1994
Yamamoto, S. (Okayama Univ. (Japan). Faculty of Agriculture) | Suto, A.
The occurrence pattern of Thujopsis dolabrata S. et Z. Saplings in the understory of an old-growth Chamaecyparis forest in the Akasawa Forest Reserve of Central Japan was investigated. The investigation using the point frequency method revealed that T. dolabrata saplings occurred more frequently on the lower parts of slopes rather than on the upper parts. By the investigation using the closest individual method, it was found that a canopy of trees of T. dolabrata, which can be a seed sources for regeneration, did not occur in stands without an understory of T. dolabrata saplings, whereas canopies of trees occurred in stands with under stories T. dolabrata saplings. Also, the density estimation by the point-centered quarter method showed that the stands with larger densities of canopy trees of T. dolabrata had their saplings more abundantly, but the density relationship between saplings and canopy trees of T. dolabrata was fitted best to a polynomial function with a saturated density of saplings. Finally, investigation showed that gap regeneration was not effective in the stand without the canopy trees as there were no gap regenerators of T. dolabrata in gaps of this stand. Several causes have been advanced for the understory dominance by T. dolabrata saplings. Results of this study, however, indicate that the present occurrence and abundance of under-story T. dolabrata saplings may be controlled mainly by the presence and abundance of canopy trees of T. dolabrata. This strongly suggest that the canopy trees of T. dolabrata must be removed to inhibit the spread of T. dolabrata saplings in the future
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