Abstract
There is a lack of information in the rural Mediterranean area about agricultural pile burning impacts on soil nitrogen (N) dynamic and the N loss. Therefore, this research aims to study the impacts of moderate (MS), and high (HS) severity burn on N transformation and N losses, compared to an unburned (C) during the first year. The experimental plots (10 m2) were established in Croatia (43°58′ N 15°31′ E), in a slope ~18°, with a southwest exposition. Five days after the burn, C treatment had a significantly higher total N (TN) than MS and HS. Generally, the runoff was significantly different between burned and C treatments. Sediment yield, concentrations, and TN loss were significantly higher in MS than in C treatment. The concentrations of ammonium (NH4-N) and nitrate (NO3-N) in the runoff, and their losses were higher in burn treatments than in C treatment. These values were high in the first three months after burn, although the peaks in later periods correspond to extreme rainfall events. Principal component analysis showed that sediment yield was associated with sediment concentration, runoff, and TN loss (Factor 1). In addition, rainfall amount and intensity were inversely related to NH4-N concentration and losses (Factor 2). The NO3-N concentration was positively related to NO3-N losses. Overall, MS treatment had severe effects on N loss and, sediment yield can be used as an indicator of soil degradation after pile burns.
Highlights
The risk of wildfires in Mediterranean areas increased with rural depopulation and the consequent accumulation of fuel in woodlands due to the lack of management [1,2], the prohibition of using fire for landscape management, and climate change [3]
NO3 -N is not produced directly by heating but is formed during subsequent nitrification of NH4 -N as a result of the burning [10,11,45]. These results indicate that high severity (HS) treatment had a severe effect on NO3 -N concentrations in runoff, as the significantly higher values were observed in HS treatment
The short-term effect showed a substantial impact on N loss in both burn treatments
Summary
The risk of wildfires in Mediterranean areas increased with rural depopulation and the consequent accumulation of fuel in woodlands due to the lack of management [1,2], the prohibition of using fire for landscape management, and climate change [3]. Burning agricultural residues in piles is a cost-effective alternative for reduction residues when the management of the landscape with fire is forbidden [4]. Pile burn is a widely adopted practice in the rural Mediterranean area for residues management [5,6] despite the environmental impacts (e.g., air and water pollution). Burning residues heat the soil (direct impacts), changing their properties depending on the severity of the burn [7]. The magnitude of post-burn nutrient loss is variable and depending on the interplay between burn severity, post-burn weather patterns, type of burned biomass, topography, soil properties, and land use [10,11,12] The varied
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