فریده عباس زاده افشار

Post-fire erosion is a main concern to society because it has inflicted serious damages in managed ecosystems. In this study, the impacts of firing and time after firing on soil erosion (using 137Cs technique) and on some selected soil chemical and physical characteristics were investigated in steep rangelands of western Iran. Three sites in rangelands with similar slope gradients and parent materials were selected, and within each site, the burnt (1, 5 and 10 years after the firing) and the unburnt treatments were studied and soil samples were collected from the five depths (0–2.5, 2.5–5, 5–10, 10–20 and 20–40 cm) with three replicates. The results indicated that soil organic matter (SOM), total nitrogen (TN), available Phosphorus (Pava), available Potassium (Kava), electrical conductivity (EC) and bulk density (BD) were significantly different between burnt and unburnt treatments for two times after firing (1 and 5 years after the firing). No significant difference by the Duncan's test was obtained for these properties between the 10 and 5 years after firing. In addition clay and sand contents, magnetic measures (χlf, χhf) were significantly differed between burnt and unburnt treatments for all the three times after firing. The results of soil erosion by 137Cs technique showed that profile distribution model (PDM) estimated the mean soil erosion rate of 38.9 and 23.02 Mg ha–1 yr–1 in the three studied years in the burnt and the unburnt rangelands, respectively. As a conclusion, firing led to increasing of soil erosion rate and altering soil physical, chemical and magnetic properties in the studied steep rangelands. Overall, the results confirmed that 137Cs technique could be used as a rapid and efficient model to determine soil degradation in the rangeland soils. The firing led to deteriorating soil organic matter and, subsequently, to declining aggregate stability and increased soil erosion and degradation in the burnt rangelands. Hence, understanding historical contexts of fire occurrences is paramount to increase our capacity for ecological transformations and management in the face of the critical situation.