role of soil and topographic features in distribution of plant species (case study: sanib taftan watershed)

the study was carried out to investigate the effective soil and topographic features on distribution of plant types in sanib taftan watershed in sistan-and-balouchestan province, iran. initially, land units map was specified by combining three maps of slope, aspect and altitude. five types including artemisia santolina- hammada salicornica, artemisia sieberi- amygdalus lycioides, artemisia lehmaniana- amygdalu slycioides, amygdalus lycioides-amygdalus scoparia, pistacia atlantica- amygdalus scoparia were identified. sampling of vegetation in the land units was conducted using linear transect method, so that presence and absence of the plant species, canopy cover, stone and pebbles, litter and bare soil percent were catculated in 50 or 100 m transects (2-4 m2 plots) in a randomized systematic method. soil sampling was done with respect to the width of each land unit (from 0-30 cm depth). principal component analysis (pca) was conducted on vegetation and plant type-environmental variables matrix. the most important and effective factors in vegetation distribution of the studied area were slope, altitude, soil texture (silt and sand) and total nitrogen and the factors related to topography (slope and altitude) were more effective than those related to the soil.