Range expansion of Phyllostachys (Poaceae) bamboo stands in a deserted area of Ikusaka village, Nagano Prefecture, central Japan: Comparisons in aerial photography between 1977 and 2014

Abstract

Range expansion of unmanaged invasive Phyllostachys bamboo stands is one of the most serious problems in ecosystem management in Satoyama area across Japan. It is feared to be accelerated by depopulation and climate change. In this study, we analyzed changes in vegetation and land use by using aerial photography between 1977 and 2014 in a deserted area in Ikusaka village, Nagano Prefecture, central Japan. We also conducted field surveys in 2017, 2018, and 2020. Consequently, the areas of bamboo stands were estimated to have expanded 13.54 times from 0.26 ha of 3 stands in 1977 to 3.52 ha of 17 stands in 2014. The annual expansion ratio of the whole area was estimated to be 1.073 ha·ha^-1·year^-1, which was in the range (0.96-1.11) of those previously reported majorly for moso bamboo (Phyllostachys edulis). Among the 17 bamboo stands recognized in the aerial photography in 2014, 14 were identified as hachiku (P. nigra var. henonis) and 3 as madake (P. bambusoides) bamboos by the field surveys. The annual expansion ratios of individual stands that were comparable between 1977 and 2014 were 1.016, 1.056 (for 2 hachiku stands), and 1.036 (for 1 madake stand). These results imply that there are risks of range expansion of hachiku and madake bamboos even in cooler hilly and mountainous areas comparable to those of moso bamboo in western Japan.