Ecological Potential Assessment of Forest Groups Using Fuzzy Set Theory and Regression Analysis of Soil Characteristics (Case Study: Khanikan Forest, Chalus, Iran)

The ecological potential assessment of forest sites introduces an index or indices that show the potential of forest site for fulfillment of special different roles of forest. Khanikan forest at Chalous needs precise investigation for assessment as indicator of lowland forests in forest ecosystems of northern Iran with considering its location position in Caspian lowland and different values. The woody groups of Khanikan forest were assessed using fuzzy set theory and regression analysis on the basis of soil characteristics including pH and carbon, nitrogen and phosphorus content. In this theory, a range of numbers with partnership possibility degree is considered instead of one number for assessment of ecological potential. 180 sample plots, each 400 m2 were designed for estimation of woody elements by systematic randomly method. Number and presence percent of woody species were recorded by measuring of canopy cover diameter. Mixed soil samples were dug in four corner and center of designed sample plots from 0-30 cm depth. Totally, 180 woody groups were recognized consisting Carpinus betulus L., Parrotia persica DC., Cratagus Pentagyna W., Querecus castanifolia C.A.M., Buxus hyrcana P., Diospyrus lotus L., Ilex aquifolium L., Ulmus glabra H., Mespilus germanica L., Alnus glutinosa L., Pterocarya fraxinifolia L., Acer insign B. Ficus carica L., and Ruscus hyrcanus L. These species were dispersed in samples plots with different ratios. The soil characteristics were incorporated in fuzzy system as input data for assessing forest groups. Triangular membership functions were defined for each characteristic. 81 fuzzy rules were recorded on the basis of investigated property. Weights incorporated in every fuzzy rule and assessment classes were constituted. Finally, assessment classes of interred data to fuzzy system were designed, separately. The assessment results showed that forest groups with pure combination of Hornbeam species had higher potential on the basis of soil characteristics compared to other groups. Stepwise regression method indicated that the ecological potential of forest groups is predictable using soil pH.