Assessing the impact of land use and climate change on the evergreen broad-leaved species of Quercus acuta in Japan

To assess the impact of Quercus acuta, a dominant species in the evergreen broad-leaved forests of Japan, and its habitat shifts as a result of climate change, we predicted the potential habitats under the current climate and two climate change scenarios using a random forest (RF). The presence/absence records of Q. acuta were extracted from the Phytosociological Releve Data Base as response variables, and four climatic variables (warmth index, WI; minimum temperature of the coldest month, TMC; summer precipitation, PRS; and winter precipitation, PRW) were used as predictor variables. The mean decrease in the Gini criterion revealed that WI was the most influential factor followed by TMC. The RF revealed a considerable increase in potential habitats (PHs) under the climate change scenarios for 2081-2100 (RCM20, 180,141 km(2); MIROC, 175,635 km(2)) relative to the current climate (150,542 km(2)). The land use variables were used for masking PH. The PH masked by land use (PHLU) was approximately half of the PH under the current conditions (74,567 km(2)). Under the climate change scenarios and 1 km migration options, the PHLU were not increased relative to its value under the current conditions. The distribution of Q. acuta was restricted by the northward shift in northern Honshu, but expanded as a result of the upward shift into the mountain areas of Western Japan. Habitat fragmentation reduced the ability of migration to respond to climate change in the lowland areas of Japan.