Abstract
The vegetation in the moor on the summit of Mt. Hiragatake, located on the boundary between Gunma and Niigata prefectures, has been changing due to an invasion of non-moor vegetation. In order to investigate how the recent climate change influenced this change, we examined the annual fluctuation of the tree-ring width of Pinus pumila around the moor and its correlation with the meteorological data. The results show that the most influential factor is the summer temperature; the tree-ring width decreased with an increase in the temperature. Rainfall, particularly in spring, has a significantly positive effect on the tree-ring width, although it is not noticeable. The negative effects of higher temperature on the growth of P. pumila contradict the previous reports. We believe that this occurred because the root of P. pumila could not develop sufficiently in the wet environment of the moor, resulting in greater water stress on the leaf. Therefore, the lower temperature shift is believed to be the factor causing the invasion of P. pumila in the moor.
