Species-specific growth patterns of trees neighboring dead oak trees caused by Japanese oak wilt disease

To test whether the effects of mortality caused by Japanese oak wilt disease on the growth patterns of surrounding trees depend on the sizes, densities, and proximities of the dead trees and whether the dependency differs among species, we examined the effects of mortality in the dominant oak species, Quercus serrata, caused by Japanese oak wilt disease on the growth rates of surrounding trees in a temperate forest in Japan. Using data on the diameters at breast height and spatial locations of trees sampled in a 1-ha plot, we evaluated the relationships between the absolute growth rate of 11 dominant species and the competition index (CI) between the neighboring tree and the dead Q. serrata tree. The CI of a focal tree was calculated from the sizes and densities of dead Q. serrata trees within a particular radius (2.5–30 m, 2.5-m intervals) of the focal tree. Of the 11 species, eight shade-tolerant species had significant positive coefficients for CI. Our results indicate that the mortality of the oak trees increased the growth rates of some shade-tolerant species, depending on the sizes and proximities of the dead trees, and that timing of the increases differed among shade-tolerant species.