Natural forest vegetation in the Hokkaido region was analyzed in relation to climatic conditions, consisting of monthly temperature, snow depth and precipitation. Understanding the relationships between vegetation distribution and climatic conditions is essential for assessing the impacts of global warming on ecosystems, because climatic conditions interactively affect the distribution of natural forest vegetation. The distribution of forest vegetation influences the cycling of carbon and water within terrestrial ecosystem, and hence is an especially important factor for ecosystems. In Hokkaido, the natural forest vegetation is classified into two types, natural subalpine vegetation and natural
Fagetea crenatae vegetation (Summergreen broad-leaved forest). A statistical model was developed with two aims: first to analyze the relationships between these two vegetation types and climatic conditions, and second, to analyze the relationships between plant functional types, deciduous broad-leaved forest and conifer/broad-leaved mixed forest in the natural
Fagetea crenatae vegetation. The statistical model enables us to compare the importance of climatic conditions in explaining the vegetation distribution, and classification rates as modeling accuracy. The results of statistical analyses using the model indicated that the distribution of natural
Fagetea crenatae vegetation was positively correlated to warmth indicators, such as the accumulated maximum temperature in autumn and a warmth index. These indicators were more useful than other climatic indicators for classifying vegetation types. There was a positive correlation between the distribution of natural subalpine vegetation and maximum snow depth. For plant functional types in natural
Fagetea crenatae vegetation, a cold indicator was the most influential factor compared with other climatic conditions. The distribution of deciduous broad-leaved forest was negatively correlated with monthly minimum temperature in coldest month. Classification rates of the statistical model for vegetation type were relatively higher than those of the model of plant functional type.
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