大雪山五色ヶ原におけるチシマザサ拡大域の地形的特徴の解析と潜在的に拡大しやすい立地の抽出

抄録

Alpine ecosystems are particularly vulnerable to the effects of climate change. Changes in temperature and snow conditions allow expansion of shrubs and changes in alpine vegetation structure globally. In Goshikigahara, in the snow-meadows of the Taisetsu Mountains, northern Japan, snowmelt time has advanced. Meanwhile, distribution of the dwarf bamboo (Sasa kurilensis) and alpine dwarf pine (Pinus pumila) has expanded, and the relative dominance of forbs (tall herbaceous species) has decreased due to changes in snowmelt and soil moisture conditions. Because S. kurilensis promotes soil drying by high transpiration, its expansion may further influence other alpine vegetation. Therefore, the ability to predict the distribution of future expansion is very useful for conservation measures. Manly’s selectivity index analyzed the preferences of S. kurilensis as it expands in terms of aspects such as slope and area solar radiation, calculated from DSM. In addition, potentially vulnerable places where S. kurilensis could easily expand were shown as a risk map. The risk map superimposes features of topographical preference from Manly’s selectively index, indicating a positive preference for easterly directions, gentle slopes, and substantial solar radiation. Furthermore, the risk map identified the most vulnerable places where Trollius riederianus, a tall herbaceous species, currently grows. The species has recently experienced a remarkable decrease. Expansion of dwarf bamboo and shrubs has been reported in alpine ecosystems all over Japan. This method is a useful tool, because it can consider the regionality of individual mountain areas, and formulate a conservation plan at key points where management costs are particularly limited.