Impact of environmental factors on distribution of wild pear (Pyrus glabra Boiss.) in Sepidan region, Fars province

In this research, several ecological characteristics of Pyrus glabra Boiss. were studied. Distribution area of wild pear was drawn on a topographic map, and altitudinal range of horizontal and vertical distribution was determined. This species is mostly distributed on altitudes above 2000 m. Thirteen sample plots, each 1000 m2 were selected considering aspect, land form and altitudinal classes. In each sample plot, various variables such as species, diameter at breast height, tree height, crown cover, origin (standard or coppice), age class, number of sprouts, associated species and forest type were measured or recorded. A soil profile was dug in each sample plot in order to study physico–chemical properties of soil. Data were tested with Principal Component Analysis (PCA). The average number of trees per plot was 8, from which 73 percent were of coppice origin. The mean diameter of breast height was 14 cm and the average of tree crown area was 11 m2. The minimum and maximum height of trees were 2 m and 7.8 m, respectively, while the mean height was 4.6 m. The western aspects contained the highest number of trees per plot, while the eastern vallies showed the highest values for diameter at breast height, trunk height, crown area, and total height. The depth of bed rock and the percent of sand and gravel were limiting factors in the soil of the studied area. The soil fertility is sufficient for plant growth in most cases and could be regarded as moderate fertile forest soils. Land form and soil fertility are the most important factors for distribution of wild pear in the studied area.