Tree coexistence on a slope: an adaptive significance of trunk inclination
Tree coexistence on a slope: an adaptive significance of trunk inclination
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斜坡上的树木共存：树干倾斜度的适应性意义
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
M. Higashi
中科院分区：
文献类型：
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作者：
R. Ishii;M. Higashi
山坡上的树通常树干向下倾斜。然而，这一显著现象的适应意义仍然难以捉摸。在这里，我们提出了一个理论模型，在一个斜坡上，这表明，树木的最大存活率，和最佳程度的树干倾斜，增加坡度变陡，清楚地表明了适应意义的树干倾斜在斜坡上。仔细检查的结果表明，树干倾斜的优势是在一个斜坡上缩短距离冠层表面，这种效果是加强陡峭的坡度。此外，该模型预测，最大的树木存活率增加与坡度更急剧较差的光照条件下。该模型的预测得到了林下物种田红杜鹃的支持，该物种生长在日本屋久岛的万年青森林中。R. tashiroi表现出更尖锐的树干倾斜度，更成功地共存于陡峭的斜坡上的优势冠层物种，Distyelae racemosum，并维持自己，即使在光线不足的条件下，坡度足够陡。这也表明，树干倾斜度是一种机制，用于层下物种与优势冠层物种共存。
Under storey trees on slopes often incline their trunks downward. The adaptive significance of this conspicuous phenomenon has, however, remained elusive. Here we present a theoretical model for the growth of under storey trees on a slope, which shows that the maximum rate of tree survival, and the optimal degree of trunk inclination, increase as the slope gets steeper, clearly indicating an adaptive significance of trunk inclination on slopes. Close examination of the results reveals that the advantage of trunk inclination on a slope is in shortening the distance from the canopy surface, and that this effect is enhanced the steeper the slope. Furthermore, the model predicts that the maximum tree survival rate increases with the slope angle more sharply under poorer light conditions. The predictions of the model are supported by an under storey species, Rhododendron tashiroi, which grows in evergreen forests on the Japanese island of Yakushima. R. tashiroi exhibits sharper trunk inclination and coexists more successfully on steeper slopes with the dominant canopy species, Distylium racemosum, and sustains itself even under poor light conditions where the slope is sufficiently steep. This also suggests that trunk inclination is a mechanism used by under storey species to coexist with the dominant canopy species.