Impact of topographical variables and soil characteristics on herbaceous forest floor in Asalem Watershed basin NO.7, Talesh

This study was carried out in Asalem Watershed basin NO.7 In order to determine relationship between the percentages of herbaceous cover with environmental factors. 17 linear transects with about 1600 m elevational gradient and 3000 m horizontal distance were selected. For this purpose, 46 plots of 400 m2 were selected by field survey within 200 m intervals along the elevational gradient. Within each plot, three quadrates (5 × 5 m) on the diagonal line were chosen and internal (1 × 1 m) quadrates were used for investigation herbaceous cover. Independent variables including aspect, slope and dependent variables including abundance and percentage of cover were recorded by using Domin’s criterion in each plot. In addition, soil samples were taken from three soil cores at each plot. The most effective factors on herbaceous cover percentage were obtained using Canonical Correspondence Analysis and multiple regression method. Results indicated that Soil characteristics showed the highest impact on percentage of herbaceous cover and the most important factors were soil organic matter, phosphorus and Potachium content. The cover percentage in the species belonging to the Poaceae increased with increasing percentage of silt.