The multiple distribution of spatial structure parameters and the models of response to them of Hegyi index of L. gmelinii natural forest, unmanaged plantation after 30% intensity thinning, and plantation managed according to target tree management after thinning were studied in Greater Khingan mountains, to provide a scientific basis for an in-depth understanding of the heterogeneity of the spatial structure of L. gmelinii plantation and for the future management.

Taking the above three kinds of L. gmelinii forest as the research objects, the multiple distribution of spatial structure parameters were analysised throught mingling degree, neighborhood comparison, uniform angle index, opening degree based on the relationship among the nearest adjacent trees, based on this, the distribution of Hegyi index of stands is analyzed.

1) From zero-element distribution, the three stands were in the mean state of serious lack of growing space, and the crop stand was mixed at zero degree with uniform distribution. The CK stand was weakly mixed with random distribution. The natural stand was moderately mixed with non-uniform distribution; 2) From the one-dimensional distribution, there were more trees in low mingling degree in the two kinds plantations, but there was little difference in the probability of different mingling degree in the natural stand. The natural stand had the most individuals randomly distributed, and the crop stand had the lowest. Three kinds of stands were concentrated in the growing space shortage or serious shortage; 3) From the quaternion distribution, tree frequencies in the three stands all presented pyramidal distribution centered on random distribution, zero degree mixing and serious lack of growth space, with the most concentrated in crop stand and the most dispersed in crop stand. The crop stand was the most concentrated and the natural stand was the most dispersed. There was no significant difference in the frequency distribution of different neighborhood comparison among the spatial structure parameter combinations; 4) The peak value of the individuals with higher Hegyi index in the three stands was random distribution, zero mixed and seriously insufficient growth space, and the ratio of neighborhood comparison. The competition intensity of natural stand was more intensely than plantation forests stand and differ significantly, with crop stand slightly less than control stand.

The study provides a scientific basis for the differences of spatial structure and tree competition between natural forests and plantations of the L. gmelinii and the effects of target tree management. The spatial structure of natural forests is richer than that of plantations, and the competition intensity of natural forests is higher than that of plantations. The spatial structure is more unitary under target tree management, weaken the competition intensity among reserved trees and promote the growth of individual tree. Combine with the purpose of forest management, this study provides a feasible method for determining felled trees, and show that the Hegyi index distribution based on multivariate distribution of spatial structure contain more information than the simple Hegyi index.