Effects of topography and management history on natural forest recovery in abandoned forest after clear-cutting in Miyazaki, Japan

We investigated factors limiting the recovery of natural forest in former large-scale conifer plantations abandoned after clear-cutting in southwestern Japan. We analyzed forest recovery status (“recovered” sites covered by evergreen broad-leaved trees, and “unrecovered” sites covered by pioneer community or nonvegetated sites) using aerial photographs and field survey. We applied logistic regression analyses to evaluate the effects of topography, construction of harvesting roads, distance from remnant forest, stand condition before clear-cutting, and prior land-use history on forest recovery. Human factors, i.e., land use and clear-cutting age, were found to affect to forest recovery more than environmental factors such as topography. Harvesting roads had the strongest negative impact on forest recovery. Forest recovery after clear-cutting of young sugi plantations also took longer than after clear-cutting of old sugi plantations or evergreen broad-leaved forests. Furthermore, areas formerly utilized as meadows recovered less successfully than those that had been managed as coppices. The influences of these factors were thought to be promoted by the advance reproduction as the regeneration sources for forest recovery. The influence of stand age before logging suggested an effect of thinning, which might alter the abundance of advanced reproduction in the understory. However, distance from remnant forest appeared to be less important. An influence of topography was also detected, but this could be partly explained by the existence of advance reproduction in the understory in certain topographic positions. Thus, our analysis suggests that regeneration sources originating from advanced reproduction in plantations play a significant role for the recovery of natural forest after clear-cutting.     

Effects of elevation and postharvest disturbance on the composition of vegetation established after the clear-cut harvest of conifer plantations in southern Shikoku, Japan

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.