Effect of Fire on Soil Physical Properties in Range Land, Agriculture and Forest Land Uses in Golestan Province

Fire has a considerable impact on vegetation and soil structure. The purpose of this study was to investigate the effect of fire on some soil physical properties of agricultural, forest, and pasture land uses in Golestan province. For this purpose, agricultural and forest land uses were selected from Gorgan province, and the pasture land use from Kalaleh as well, which were exposed to fire. Soil samples were taken from three surface (0-5cm) and subsurface depths (5-15 and 15-30 cm) for each land use in triplicate. Meanwhile, the control (non-fire) was sampled similarly. Independent t-test was carried out at p < 0.05 to compare differences between soil properties in burned and control areas. The results showed that clay content, mean weight diameter of aggregates (MWD), porosity, air capacity, structural stability index (SI), Dexter S index, and organic carbon were significantly (p < 0.05) decreased at the depth of 0-5 cm in all land uses. So that in forest, pasture, and agricultural land uses the decreasing contents were 24, 11, and 6 % for clay, 47, 41.9, and 7.4% for MWD, 10, 8, and 9 % for porosity, 34.6, 21.4, and 27.3 % for air capacity, 25.6, 7.4, and 11.3 % for SI, 19.7, 15.4, and 7.3 % for Dexter’s S index, and 8, 9.6 and 13.7 % for organic carbon, respectively, while decrement percentages of these properties were not significant at subsurface layer. Burned soils bulk density significantly (p < 0.05) compared to the control at the depth of 0-5 cm, which increment percentages of bulk density in forest, pasture, and agricultural land uses were 11, 8, and 6 % respectively, but it wasn’t significant at the subsurface layer.