effect of rangeland fire on soil physical properties and water infiltration parameters using principle component analysis

annual fires might change many soil physical properties in semi steppe rangeland.the objective of this study was to investigate the impact of fire on soil physical properties and soil water infiltration parameters in semi-steppe rangeland of karsanak region in chaharmahal and bakhtiari province. therefore, several sites were chosen which were affected by fire at three, two and one years prior to this study (i.e. 2008, 2009 and 2010, respectively). soil water infiltration was measured using tension infiltrometer in 54 points of the study sites. since the soil samples were taken from to depth (0-10 cm and 15-25 cm) of each site, the numbers of soil samples for laboratory analysis were 108. independent t-test and principle component analysis (pca) was used to assess the difference between the measured properties at the burned and control sites. the results showed that aggregates stability coefficients (mwd and gmd) in the surface layer significantly reduced in 1 and 2 years after fire compared with control areas. water dispersible clay (wdc) and bulk density significantly increased in surface layer of all burned areas compared with control areas. saturation hydraulic conductivity significantly decreased in burned areas in 1, 2 and 3 years after. the results showed that annual fires occurs have meny negative effects on soil physical properties cause to shallow, low water retention capacity and high risk of erosion in semi steppe rangeland.