Comparison of community structure and growth between the alpine dwarf shrubs Rhododendron aureum and R. brachycarpum on the Yatsugatake range, central Japan

Abstract

Rhododendron aureum and R. brachycarpum are species of the Japanese alpine zone whose altitudinal zonation was determined by the last glacial stage. We compared the ecological features of the two species in a mixed community on the Yatsugatake range. A productive structure diagram showed that R. brachycarpum can absorb light efficiently by arranging its leaf mass in an upper layer and developing a more horizontal orientation of both the shoots and individual leaves in comparison with R. aureum. The C/F ratio for R. brachycarpum was 6. 52, and was almost the same value (5.99) in a mixed community. The ratio for R. aureum was lower (2.50) and decreased to 0.77 in a mixed community. Since R. aureum cannot gain sufficient light in a mixed community, its tree-ring width here was about half of that in a pure community, and there was also a decrease in the number of leaves. These results suggest that R. brachycarpum shows superior substance production in a mixed forest