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Abstract

The epidemic of mass mortality of oak trees has affected secondary deciduous broadleaved forests that have been used as coppices in Japan. The dieback of oak trees formed gaps in the crown that would be expected to enhance the regeneration of shadeintolerant pioneer species. However, foraging by sika deer Cervus nippon has also affected forest vegetation, and the compound effects of both on forest regeneration should be considered when they simultaneously occur. A field study was conducted in Kyôto City, Japan, to investigate how these compound effects affected the vegetation of the understory layer of such a forest. The presence/absence of seedlings and saplings was and Cleyera japonica, also had the highest survival probability. Deer-unpalatable species such as Symplocos prunifolia and Triadica sebifera had higher colonization rates in the gaps, while the deer-palatable species Aucuba japonica had the smallest survival probability. The gaps thus resulted in promoting the colonization of deer-unpalatable plant species such as Symplocos prunifolia and Triadica sebifera. It might be forecasted that such deer-unpalatable species will dominate the gaps created or affected by the mass mortality of oak trees. The epidemic of mass mortality of oak trees has affected secondary deciduous broadleaved forests that have been used as coppices in Japan. The dieback of oak trees formed gaps in the crown that would be expected to enhance the regeneration of shade-intolerant pioneer species. However, foraging by sika deer Cervus nippon has also affected forest vegetation, and the compound effects of both on forest regeneration should be considered when they simultaneously occur. A field study was conducted in Kyôto City, Japan, to investigate how these compound effects affected the vegetation of the understory layer of such a forest. The presence/absence of seedlings and saplings was observed for 200 quadrats sized 5 m × 5 m for each species in 1992, before the mass mortality and deer encroachment, and in 2014 after these effects. A hierarchical Bayesian model was constructed to explain the occurrence, survival, and colonization of each species with their responses to the gaps created or affected by the mass mortality of oak trees. The species that occurred most frequently in 1992, Eurya japonica, Quercus glauca, and Cleyera japonica, also had the highest survival probability. Deer-unpalatable species such as Symplocos prunifolia and Triadica sebifera had higher colonization rates in the gaps, while the deer-palatable species Aucuba japonica had the smallest survival probability. The gaps thus resulted in promoting the colonization of deer-unpalatable plant species such as Symplocos prunifolia and Triadica sebifera. It might be forecasted that such deer-unpalatable species will dominate the gaps created or affected by the mass mortality of oak trees.