Estimating the Competition Indices and Diameter Growth of Individual Trees through Position-dependent Stand Survey.

Woo-Kyun Lee²

 

Abstract: In this study, a number of distance-dependent competition indices on tree-level which incorporate the
tree sizes and distances to competitors, and traditional stand-level density measures were estimated from the data compiled with position-dependent survey in a Pinus densi/lora stand. The performance of the estimated competition indices was examim•d by comparing the relationship with the diameter growth, and a dbh growth function, in which the competition index is considered as a one of influence factors. are developed. In the searching method of competing trees, the competition index estimated with 30 competition interrupting angle showed the highest correlation with the annual dbh growh, while the expanding the competing zone distance had no significant effect on the performance of competition index in estimating annual dbh growth. The most of the examined stand-level competition indices, based on distance-dependent single-tree competition indices, were evaluated to describe similarly the stand competition status. As a result of part al correlation analysis in which the effect of age and site index are eliminated, Alemdag's mean competition index and relative spacing index were determined to have the highest correlation with dbh. The relative spacing index, which can be easily measured in field without measuring the position of individual trees, was considered to be a better suited one for estimating mean dbh of a stand.
Among distance-dependent competition indices on tree-level, Hegyi's competition index showed the best performance in their correlation with annual dbh grov,ih, if eliminated the effect of site index and dbh. This enabled to derive the following annual dbh grov.1:h function of individual trees which incorporate age, dominant height, dbh and Hegyi's competition index as influence factors.

This function is coincided to the grov.1:h principle in which site index has a positive effect on the annual dbh growth, while high age or competition causes to reduce the annual dbh growth, and can be used as a function in single tree growth model.

 

Key words: distance-dependent comPetition index. tree-level comPetition index. stand-level density, Position-dependent survey, annual dbh growth function, single tree growth model