The effect of fire on soil quality in semi-steppe rangelands of Karsanak, Chaharmahal and Bakhtiari

Occurring fire in rangelands is one of the main degradation factors of soil and ecosystem. The objective of this study was to investigate the impact of fire on some crucial factors of soil quality in semi-steppe rangeland of Karsanak region in Chaharmahal and Bakhtiari Province. Therefore, several sites which were affected by fire at three, two and one years before this study (i.e. 2008, 2009 and 2010, respectively) were chosen. Soil water infiltration was measured using tension infiltrometer in 54 points of the study sites. Since the soil samples were taken from depths (0-10 and 15-25 cm) of each site, the numbers of soil samples for laboratory analysis were 108. Independent t-test (P=5%) was used to assess the difference between the measured properties at the burnt and control sites. The results showed that in the burnt areas compared with control areas, saturation hydraulic conductivity and basic water infiltration decreased significantly in 1, 2 and 3 years after fire. Also, the soil organic matter and mean weight diameter of aggregates (MWD) in surface layer reduced significantly in 1 and 2 years after fire. Particulate organic matter (POM) significantly decreased in surface layer of the burnt areas compared with the control areas, while their differences were not significant in sub-surface layer. Furthermore, soil water dispersible clay (WDC) and bulk density increased significantly in surface layer of all burnt areas compared with control areas. The study results showed that fire had immediate and direct impact on soil physical properties and organic matter and therefore reduced the soil quality of rangelands.