The Forest Structure and Tree Death Rate of Forest Stands Damaged by Japanese Oak Wilt in Yamagata Prefecture

概要

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We evaluated forests that are vulnerable to oak wilt, and prospects of regenerating the damaged trees. Most canopies of Quercus crispula trees died within 10 years after the spread of the oak wilt, while the canopies of Q. serrata survived by approximately 40% or higher rate. The average vegetation coverage at canopy layers in a severely damaged forest was 28% in Q. crispula dominated stands and 47% in Q. serrata dominated stands. Furthermore, a small number of tree species in the sub-canopy layers of Q. serrata dominated stands. Thus, Q. crispula dominated stands are expected to lack canopy layers for many years, while canopy layers can be expected to be restored in Q. serrata dominated stands. However, regeneration by seedlings may not occur in either of the oak stands, because Camellia japonica and other evergreen broad-leaved undergrowth species will keep occupying the shrub layers. Also, since most trees that have died from oak wilt have toppled down within 5 years, the falling of dead trees may cause problems to the infrastructure, such as blocking of roads and cutting of the electric wire.