In the Taisetsu Mountains of Hokkaido, dwarf bamboo( Sasa kurilensis ) has increased the distribution area in alpine meadow probably due to recent acceleration of snowmelt time, and it may cause a declination of alpine vegetation. However, there are very few studies on the responses of dwarf bamboo to climate change. The purpose of this study is to clarify the expansion mechanism of dwarf bamboo to alpine region under changing climate in terms of photosynthetic activity, growth and productivity. The maximum photosynthetic rates were the highest in the montane site, decreased with elevation down to 73% in the alpine site. Similarly, leaf area index decreased with elevation down to 68%. Culm density was about 20(m⁻²) in the montane site, while it was about 60(m⁻²) in the alpine site. Culm height was 180cm in the montane site, while it was 90cm in the alpine site. Therefore, resource allocation for height elongation of individual culms was predominant in the low altitude in which competition for light capture is severe. In contrast, an increase in culm density by frequent branching was accelerated in the alpine area by which the number of leaves was enhanced, resulting in high productivity under the conditions of high irradiance. High morphological plasticity may enable dwarf bamboo to expand rapidly in alpine regions under warming climate.