Alpine plants are distributed in the mosaic patterns reflecting fine geographic features. Climate changes with global warming should influence vegetation diversity quickly. In the Taisetu moutains, northern Japan, soil drying due to earlier snowmelt may influence the distribution of Pinus pumila, which has the biggest biomass in alpine ecosystem. We aimed to quantify the expansion area and to specify the environmental factors affecting the growth of P. pumila. Comparisons of aerial photographs between 1977 and 2009 revealed that the expansion area of P. pumila was 12707㎡/ 50 ha during the past 32 years, especially toward the southeast direction. In the field survey, annual shoot growth during last 20 years was measured for 20 P. pumila patches. Then, factors affecting shoot growth were analyzed with reference to summer temperatures, radiation hours, precipitation, snowmelt days, minimum spring temperature, patch size, and direction as explanatory factors. The GLMM revealed that shoot growth was accelerated when minimum temperature in May was low and on the south- and east-facing direction of patches. These results indicate that protection with snow in early spring is crucial for shoot growth to reduce the risk of frost damage for vegetative growth of P. pumila.