Application of Incomplete Competition Mean Index to Analysis of Forest Plant Competition

The competition among the dominant trees in the plots was analyzed in the Qingshan Lake area by plot setting with typical sampling method and on the spot survey. Four dimensional indexes were measured in the study. One dimensional indices included relative DBH, relative tree height and relative crown diameter. Two dimensional indices included relative growth elevation, and relative crown projection. Three dimensional indices included relative stem volume and relative crown volume. Four dimensional indices included relative crown ecological space. The two dimensional indices, three dimensional indices and the four dimensional indices were newly proposed as incomplete mean indicators based on the biological significance of the measurement factors. The competition status of the trees in the sampled plots was analyzed by above four categories of indices, and the simple correlation analysis and principal component analysis were conducted with the indices. The results showed that the relative DBH, relative tree height and relative crown diameter could not accurately reflect the competitive ability of the trees, whereas the relative crown ecological space, relative crown volume, relative crown projection would significantly change along the variation of stand density, which might well reflect the competitive situation of the trees. Among which the relative crown ecological space was the most suitable index to indicate the comprehensive competition of trees in the stand.