Typhoons will become more frequent and more intense under future climate change conditions. Forestry practices are needed that will reduce windthrow events and enhance resilience after windthrow damage. We aimed to explore management scenarios that can recover the above-ground biomass (AGB) after windthrow damage under climate change.
We used the LANDIS-II model to simulate the recovery through 2055 of AGB in the national forests (42°3’ N, 139°5’ E, 0–1300 m elevation, and 348 km2) in southern Hokkaido, Japan, which was hit by typhoons in late August 2016. Referring to the National Forest Inventory, the spatial distribution of tree species before windthrow damage was set. The distribution of dwarf bamboo (Sasa kurilensis) in the understory, which prevents the establishment of the other plants, was estimated from the overstory tree density. Three post-windthrow management scenarios were simulated—leaving the damaged tree on the site (CL), salvaging logging and planting the same tree species as before (SLPL1), and salvaging logging and planting different tree species that adapt to the warmer environment (SLPL2). Three future climate conditions were used to evaluate impacts of climate change—the current climate conditions and the two statistically downscaled RCP2.6 and 8.5 scenarios of the MRI-CGCM3 model.
Results/Conclusions
The impact of post-windthrow management on the AGB was higher than the impact climate change will have through 2055. In the SLPL1 and SLPL2 scenarios, the mean AGB in 2050 was 7.7–11.2 times higher than the mean AGB of the CL scenario. In the CL scenario, dwarf bamboo prevented the establishment of other tree species, and the AGB in 2055 could not reach the level it was at before windthrow damage. Planting an adapted tree species in the SLPL2 scenario increased the AGB under the RCP 8.5 scenario. In natural forests, the removal of dwarf bamboo associated with site preparation for natural regeneration encouraged the establishment of pioneer species such as Betula ermanii.
From the results, salvage logging and plantation after windthrow damage successfully recovered the AGB. Natural regeneration, which can increase plant diversity, required the removal of dwarf bamboo. Although the impact of climate change was relatively small, it will affect the spatial distribution of dwarf bamboo in the long run, indicating the need for a longer-term simulation and forest planning.