Effects of Flooding and Fire on Aggregate Stability: A Case Study in the Soils of Lakan Nursery in Guilan Province

This study was conducted in order to investigate the effects of flooding and fire on status of aggregate stability and soil structure in Lakan forest in Guilan province. Soil sampling was carried out with three replicates from three depth 0-3، 3-6 and 6-9 cm in the representative locations subjected to flooding، fire، and the control site. The aggregate stability was measured by MWD، GMD [H1] and fraction dimension indices by dry and wet sieve tests. Results of this study indicated that in flooded soil، clay and silt values (at all depths)، organic carbon، bulk density، and aggregate density values (at the first depth i. e. 0-3cm) significantly increased، but aggregate density value (at the second depth i. e. 3-6cm) and sand content (at all depths) significantly decreased as compared to the control soil (no flooding and no fire). In burned soils، silt values (at the second depths) and bulk density values (at the first depth) significantly increased and clay and OC values (at the first depth) and CEC significantly decreased as compared to the control soil. Investigation on aggregate stability indices (MWD، GMD and D) showed that these characters increased at all depths in flooded soil and decreased at the first depth of the burned soil as compared to the control soil. This happened probably due to changes in the clay and OC. Furthermore، aggregate stability indices in wet sieve test had stronger relationships with soil properties. Generally، the effects of flooding and fire phenomena were different: flooding improved aggregate stability، but fire produced undesirable effects.