Quantitative study on the factors determining the distribution of Abies mariesii using a statistical decision-tree model

Previous studies pointed out that the distribution of Abies mariesii is determined by snow pressure, strong wind, topography, and so on. However, the ranking of the factors based on their importance has not been assessed quantitatively. Using a statistical decision-tree model, this study ranked the factors (Warmth Index, snow depth, elevation, slope, aspect, and snow pressure) around the Joetsu mountains. We found that more important factors were (1) Warmth Index, (2) snow depth, and (3) slope, or (1) Warmth Index, (2)snow depth, and (3) Warmth Index in the order of importance. The former well explained the distribution of Abies mariesii around Okushiga region, while the latter with elevation well explained the distribution around Mt. Naeba. Some of these factors are likely affected by the global warming, thus, this paper also discussed that the distribution of Abies mariesii may considerably change under the climate in future.