Abstract:

Forest stand spatial structure reflects structure associated with trees spatial position,which is generally described by mingling，neighborhood comparison and neighborhood pattern.The most important thing for calculating the three spatial structure indexes is determining the target's nearest neighbor trees and the number of them.Voronoi diagram is one of partition patterns for spatial.This article regards individual tree as a planar point and builds Voronoi diagram and Delaunay triangulated network based on Voronoi diagram's nearest and adjacent characteristics,which have the following features:the number of nearest neighbor trees equals the number of corresponding polygon edges in Voronoi diagrams,the distance between the target trees and the nearest neighbor trees equals the length of corresponding polygon edges in Delaunay triangulated network,and the angle between any two nearest neighbor trees equals the angle between two corresponding edges in Delaunay triangulated network.With testing in the plot in Mangrove Nation Natural Reserve at Zhanjiang,this article comparative analysises the outcomes of calculating the spatial structure indexes based on Voronoi diagram and Delaunay triangulated network and the outcomes of traditional algorithms which the number of the nearest neighbor trees is 4.The result shows:the outcomes have significantly correlation and agreement between the two when calculating mingling and neighborhood comparison,but the outcomes exist remarkably difference when calculating neighborhood pattern.Because selection is in all direction when build Voronoi diagram to determine the nearest neighbor trees,the neighborhood pattern values are less than the values of traditional algorithms,but Delaunay triangulated network structures reflect well the distribution pattern of individual on horizontal ground,and also the research of forest stand spatial structure,which based on Voronoi diagram and Delaunay triangulated network,do not need measure distance and calculate angles between the target trees and the nearest neighbor trees.

Key words: forest stand spatial structure, Voronoi diagram, Delaunay triangulated network, mingling, neighborhood comparison, neighborhood pattern