Quantifying of competition among single trees by the overlap of influence zones and its application to the selection of trees for thinning in a Japanese larch [Larix leptolepis] plantation
1998
Wang, H. (Tottori Univ. (Japan)) | Ogasawara, R. | Sano, J.
To quantify the competition among single trees in closed stand, the radius of influence zone of a single tree was estimated by the ratio of diameter at breast height of forest tree to that of an open-growing tree with the same height. Competition index and dominant index were calculated from the overlap among the influence zones of single trees. Two 900 m2 sample plots were conducted in a 40-year even-aged plantation of Japanese larch (Larix leptolepis Gord.). The small trees had a higher competition index and a lower dominant index, and vice versa. Competition of single trees could be estimated by the dominant grade calculated from the competition index and the dominant index. The decline of the competition index and the dominant index of single trees was shown by the reduction of overlap among residual trees after thinning, based on the dominant grade. The effects of different thinning methods on single trees were revealed; competition index and dominant index were considerably reduced by the thinnings of understory and overstory, respectively
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