ارتباط بین خشکیدگی درختان بلوط ایرانی با عوامل محیطی و خصوصیات جنگل‌شناسی در جنگل حفاظتی دنا

In recent years, fundamental changes in the ecosystems of Zagros forest structure have occurred, including the decline of brant’s oak (Quercus bratii Lindl.) that is main species in this region. So this research intends to study trees decline in relation to sylviculture, topography, and soil characteristics. For this purpose, first, parts of forest that showed oak decline were identified by field survey and three plots were selected in every land form (elevation, slope, geographic directions and different land forms). 23 plots were totally selected in Dena area. In each plot physiographic variables, sylviculture parameters were recorded and then soil samples were collected for soil physicochemical experiments. Trees were categorized in three classes including low (0-15%), medium (15-30%) and high decline (>30%). Results of topography showed that high slopes and south directions had more decline, but soil factors showed no significant correlation with decline. The sylviculture results showed that low and medium diameter classes, the greater canopy area and the lower height of trees were more declined. In the other side, correlation results showed positive significant relationship between coppices shoot and decline percentage. In fact, trees in the form of coppice had the most declines. In general, it can be said that topography and forestry factors in the studied area are among the important factors affecting distribution of oak trees decline and situation and amount of dieback especially for small and coppice trees.