Observations and predictions of wind damage to Larix kaempferi trees following thinning at an early growth stage

Abstract

It is important to find effective forest management strategies to reduce wind damage risk, which is expected to increase due to climate change and increasing areas of planted forests. Thinning is one of the most important forest management activities, but it initially increases tree vulnerability due to an increase in wind penetration into the forest. In this paper, we analysed the damage to trees remaining after the thinning of Larix kaempferi (Lamb.) Carr. at an early growth stage in order: (1) to find the critical factors related to wind damage using statistical models and (2) to calculate the critical wind speeds for damage using a modified version of the mechanistic model GALES. Tree damage caused by a storm in 2006 was examined in plots of different stem densities (300, 500 and 1000 stem ha(-1)), which were thinned at a young age in a replicated silvicultural trial. Subsequently, tree-pulling experiments were conducted to obtain the parameters required in the GALES model. The logistic regression models based on the observations indicated that a longer crown length and a faster annual increase in crown width were significantly related to a reduction in damage occurrence. Estimation of wind damage to trees using GALES did not agree with the observed damage, probably due to the model not accounting for the influence of neighbouring trees and the degree of tree acclimation to the local wind climate after thinning. However, our research is based on only one example of tree damage in stands with different stem densities. Furthermore, our assessment might be biased because we used the trees remaining after the storm to derive parameters for the GALES model, and these trees might on average be more resistant than the storm damaged trees.