Study of decline effect on structure of central Zagros forests

The aim of this study is to evaluate the effect of decline on the structure of central Zagros forests. For this purpose, an area of about 32 hectares located in Khoramabad forest was inventoried using full calipering method. The values of Clark and Evans index were calculated 0.62 and 0.95 for before and after the decline respectively. These values showed a change from cluster positioning to random pattern with effect of decline in spatial distribution of trees. Also, the result of uniform angle index were calculated 0.51 and 0.48 for before and after the decline respectively that showed the random arrangement of nearest neighbors in both situation. The mean value of mingling index was calculated 0.06 and 0.09 for before and after degradation respectively which represents a slight increase in mixture. Also, the results of the Shannon-Wiener index, was 0.21 for before decline and 0.30 after decline that showed a slight increase in species diversity. The canopy area size index was calculated 0.71 and 0.50 respectively before and after the decline indicating that being dominant of the reference trees (Trees of center structure groups) than their neighbors. This dominance has been decreased by decline effect. Size difference of canopy area index calculated 0.48 and 0.56 respectively before and after the decline that the area difference between s reference trees and neighbor trees has been increased with influence of decline. The results of these indices can reveal forest figure to managers and planners which could be used to determine of created changes caused by natural processes in optimized management of forest.