engleski

Impact of wildfire on rock weathering and soil properties in Zadar County, Croatia

Abandonment of agriculture in recent decades has lead to increase of wildfire occurrence in Mediterranean region. Wildfire results in higher rock weathering rate, change in soil physical and chemical properties and finally increase of soil erosion. In September 2012 a wildfire occurred on an abandoned agricultural land in a small area between villages Jovići and Radovin, Zadar County. Within a few days after the fire we installed six micro-erosion meter measuring sites accompanied by sets of buried rock tablets in order to measure post-fire weathering rate. Four measuring sites were installed on rocks exposed to wildfire, while two sites were set within a few meters from fire front and served as control. In order to investigate the change in soil properties, soil samples were collected in four locations (three in fire-exposed and one in control location) at two depths (0-3 and 10-15 cm) immediately after the wildfire. Furthermore, physical and chemical properties of eroded material sedimented at the bottom of the slope were analysed from three depths, sampled six months after occurrence of wildfire. Micro-erosion meter measurements showed increased weathering of fire-affected rocks (compared to non-affected ones), while tablets buried in fire-affected soil showed lower weathering rates (compared to non-affected ones). The most significant difference in chemical composition of fire-exposed and non-exposed soil (sampled immediately after wildfire) can be observed in increase of P2O5 and K2O content within 0-3 cm layer (from 1.4 to 41.5 mg P2O5/100 g of soil ; 25.5 to 150 mg K2O/100 g of soil). Furthermore, pH of fire-affected soil increased as well as humus content. Sediment texture analysis of eroded material (sampled 6 months after wildfire) showed higher percentage of fine silt and clay compared to samples collected immediately after fire indicating erosion of finest soil particles. Chemical analysis of this sediment showed clear processes of leaching of nutrients (P2O5 and K2O) into deeper layers of soil and enrichment in humus content.

wildfire; rock weathering; soil properties

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