Abstract
We clarified the effect of advance regeneration on natural forest recovery after clearcutting of conifer plantations over the mid-term observation period (12–14 years to allow formation of the forest canopy). We established understory-intact plot (UI-plot), where advance regeneration (AR; DBH more than 1 cm before clearcutting) were retained, and understory-cleared plot (UC-plot), where all ARs were removed at felling of conifer crops. We surveyed individual density, species richness, and tree height with reference to different regeneration origins 1 year after and 12 or 14 years after clearcutting. Then, we compared the structural changes in UI-plot with that in UC-plot. The resprouted AR in UC-plot has provided the same effect as the retained AR in UI-plot in forming their height distribution patterns and stratification over a mid-term recovery process. We also found that individual density and species richness attributed by the individuals of newly established seedlings after clearcutting (SE), have contributed to the stand development in the both plots. Furthermore, SE was found to have a large contribution to forest recovery in terms of tree density and species number, while its significance for the recovery of gravity-dispersal, lucidophyllous trees was limited. We concluded that the advantage of AR retention is limited to the fast recovery of forest structure at the early stage after clearcutting, and mostly disappeared over a mid-term observation period as far as abundant advance regeneration was sufficiently accumulated and surrounding seed sources were effectively secured.
Highlights
After the Montreal Process, the implementation of Sustainable Forest Management has been emphasized to promote forestry productivity and the conservation of biodiversity through appropriate ecosystem management (Nagaike2000; Eycott et al 2006; Yamagawa et al 2008, 2013; Ramirez-Collio et al 2017)
The results of this study revealed that, over a mid-term forest recovery, the cutting advance regenerations (ARs) at clearcutting resulted in increased resprouted advance regeneration (R-AR) in the understory-cleared plot (UC-plot), which compensated the lack of surviving advance regeneration (S-AR) together with individuals originated from newly established seedlings (SE)
The advantage of AR retention was thought to be limited to the maintenance of tree population and stratification at the early stage of forest recovery
Summary
After the Montreal Process, the implementation of Sustainable Forest Management has been emphasized to promote forestry productivity and the conservation of biodiversity through appropriate ecosystem management (Nagaike2000; Eycott et al 2006; Yamagawa et al 2008, 2013; Ramirez-Collio et al 2017). In Japan, conifer plantations have increased due to extensive afforestation after WWII. These plantation areas include numerous sites inappropriate for planting forestry, and forest management has been abandoned in some plantations due to a decline in timber prices. To restore the ecosystem services and increase biodiversity in these areas, as well as realize sustainable forest management goals, forest restoration through integrating natural regeneration is considered necessary (Zerbe 2002; Ito et al 2013; Onaindia et al 2013; Yamagawa et al 2013; Brown et al 2015). Over the short-term, advance regeneration contributes to forest recovery and the generation of semi-natural forests in a warm-temperate region
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