Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest

Based on the discussion of relationships between thinning and wind damage, and published information, a method for estimating risk ratios of wind damage was developed. Estimations of risk-ratio forPinus thunbergii trees and stands were deduced from stem bending theory and coefficients characterizing wind profile, distribution of branches and optical stratification porosity. The results showed that if the value of constant β in the branch distribution-model equals the attenuation coefficient αs in the wind profile model for a single tree crown, then the parameter H/D1.33 (height over stem diameter cubed) can be used to compare and evaluate the risk-ratio of wind damage for individual trees. The same method can be applied to stands using the coefficient of wind profile in a stand, i.e. attenuation coefficient α, the coefficient from distributions of optical stratification porosity, i.e. extinction coefficient ν, and the parameter D1.33. The application of parameter H/D1.33 and the process of determining risk ratios of wind damage for stands were also given in the paper.