General Commission for Scientific Agricultural Research-
Administration of Natural Resources Research
Damascus University, Faculty of Agriculture
The environmental factors, particularly climatic and topographical ones (altitude above sea level, slope exposure, parent rock nature and soil) in the structure of forest vegetation over the northeast parts (from Rakhla to Wadi al-Kren) of Harmoun mountainous range (high mountains area) in the southwest region of Syria were studied. For this purpose, 30 line transects of 100 m long were taken (Lin intercept Method) covering the original directions within two heights
(below and over 1500 m). The rigid calcareous rocks and fragile marl soil were also exemplified. The criteria of relative density, coverage, and frequency were also adopted for the wooden species; while the importance value criterion and similarity index (Sorensen Index) were adopted for forestry vegetation. The plant density was estimated by dimensional methods (Nearest Individual Method).
The results have shown the significance of altitude effect on forest vegetation.
Structure for Quercus brantii only, where dry species such as (Amygdalus orientalis, Crataegus azarolus, Quercus calliprinos) were dominated on low altitude (less than 1500 m), whereas) Quercus boisseri, Quercus brantii) were dominated in high altitude (over 1500 m ).
Moreover, the slope exposure has affected the measured criteria in both heights, where dry species were concentrated on the southern and eastern slopes and less-dry species on the northern and western ones. The interaction of slope exposure and altitude has also affected the Structure of forest vegetation for (Quercus boisseri), only. so the results have obviously shown noticeable similarity between exposure and heights.
In addition, the results have revealed a large effect of soil and parent rock on the Structure of forest vegetation, where (Cistus creticus) was widely spread on fragile marl soils.
The forests of this area are characterized by rich plant biodiversity. This area is environmentally pressed by soil erosion, deforestation, overgrazing and wooding that resulted in degradation and area shrinkage. Therefore, it is inevitable to manage natural and human resources in an integrated and sustainable manner.