Investigation on principal factors determining stand structure in Oak forests of Zagross

The effects of several factors and variables which determine forest stand structure, aren’t equal. Some of these factors, which have large effects, named as principal factors or principal components. Diagnosis and separating of this principal factors from others are very important. One of the suitable methods for determining of principal factors, is Principal Component Analysis (PCA).
In this research by PCA method, 12 forest stands of Oak (Quercus persica) and Pistachio (Pistasia atlantica), with different climatic and topographic conditions, selected and classified then by using of 31 environmental variables and structural characters, those principal factors were analysed. Results showed that variations between regions is relatively high, where 66.2 percent of total variations display in the first three axis. Regions of Cheshmehdaulat, Dalabpain and Nakhjirbala have minimum variability and regions of Melagavan, Meimeh, Nakhjirpain and Tajarian have maximum variability. In comparison to regions, we can named first axis as diameter or age axis and named second axis as almost species diversity. Variation between variables is too relatively high, where 61.3 percent of total variations display in the first three axis. Percent of health trunk, species diversity, tree density, number of dry branches, mean diameter at breast height and total canopy have larger variations in comparison to other variables.