Effects of elevation and postharvest disturbance on the composition of vegetation established after the clear-cut harvest of conifer plantations in southern Shikoku, Japan |
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Authors: | Atsushi Sakai Takahisa Hirayama Shigenori Oshioka Yasumasa Hirata |
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Institution: | (1) Shikoku Research Center, Forestry and Forest Products Research Institute, 2-915 Asakura nishi-machi, Kochi 780-8077, Japan;(2) Nishinihon Institute of Technology, Kochi, Japan |
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Abstract: | Large areas of previously clear-cut conifer plantations have been recently abandoned in Japan. We investigated the vegetation
in the clear-cut sites and examined the environmental factors affecting species composition of the vegetation. We set up 32
study sites, each composed of several study plots (5 × 5 m), ranging from 220 m to 1060 m a.s.l. Elevation and warmth index
(cumulated thermal quantity) were the primary factors affecting the species composition, with clear-cut areas showing a smaller
effect in the nonmetric multidimensional scaling (NMS) ordination. Two-way indicator species analysis (TWINSPAN) divided the
32 study sites into ten vegetation groups, clustering the sites by elevation or by postharvest disturbances (i.e., replanting
or browsing of Sika deer). Deciduous trees and shrubs were significant in the vegetation cover at higher elevations, while
they were less so in areas of high Sika deer populations. We also investigated the abundance of old-growth species, which
are expected to regenerate where the clear-cut site is abandoned. Evergreen Quercus and Castanopsis saplings were abundant at low elevations (<600 m), suggesting that they will successfully regenerate. The sapling densities
of Abies firma and Betula grossa were significantly large where a clear-cut site was adjacent to natural forest, which is expected to act as a seed source.
This implies that degraded deciduous forests may establish after clear-cutting at intermediate and high elevations (>600 m)
if the clear-cut site is distinct from seed sources. It is argued that the preservation of natural forests is critical for
the regeneration of old-growth species. |
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Keywords: | Clear-cutting Multivariate analysis Old-growth species Regeneration process Secondary succession |
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