Impact of Urbanization On Some Soil Characteristics In Ziarat Watershed Golestan Province.

Rapid growth of urban population and the expansion of urban areas have led to changes in urban forest structure and composition, and consequently changes in some soil characteristics. The purpose of this study is to quantify the effects of urbanization on some soil characteristics in Ziarat watershed, a subbasin located in southern Gorgan, center of Golestan province. The study area was divided into four land uses, forest, pasture, cultivated and urban. Soil samples of 0 to 30 cm depth and analysis of them were taken by completely randomized split-plot with two aspect geography north and west, and five replication designed. The results indicated that Mean weight diameter (MWD) of soil particles in the pasture increased but it decreased in the urban and cultivated land respectively with respect to forest. Bulk density (BD) increased and soil infiltration rate decreased after land use changed from forest to pasture, cultivated and urban respectively. Organic carbon (OC) and the total nitrogen decreased in the urban, cultivated and pasture respectively with respect with the forest. The soil porosity decreased in urban and pasture respectively with respect to the forest but in cultivated land use increased that it due to tillage. Density soil decreased in pasture, cultivated and urban soils respectively with respect to the forest. The Ph increased in the cultivated, pasture and urban respectively with respect to the forest. The EC increased the most amounts in the urban, cultivated, pasture respectively with respect to the forest. Therefore, it is important to recognize the possibility of future contaminant because Ziarat watershed is above Gorgan, center of Golestan province, this study demonstrated that trend of degradation and mis management increase hazard of urban floods, sediment problem and human health due to water pollution in main city of province.

 Keywords Urbanization, soil characteristics, MWD, infiltration