engleski

Soil CO2 emissions from burning slash piles in a Mediterranean rural area (Croatia)

Burning slash piles is very often used by land managers in the Mediterranean rural areas. These methods are preferred because they allow the removal of large quantities of unwanted biomass in a controlled environment. However, carbon released during biomass burning contributes to atmospheric loading of greenhouse gases and demands additional research about soil CO2 emission. To supplement this issue, two experimental pile burns, on March 18th 2019 were established in the Mediterranean part of Croatia. The study area is located in the rural area, near Vrana settlement (43°58'N 15°31'E ; 20 m a. s. l.), with a slope of ~18°, southwest aspect, and soil type classified as Leptosols. Moderate severity burn (MS) was filled with 10 kg m-2 barley straw, and high severity burn (HS) with 10 kg m-2 barley straw and 15 kg m-2 vine stem. Unburned treatment (UB) with natural vegetation ; meadow plants (Foeniculum vulgare Mill., Elymus repens (L.) Gould, Digitaria sanguinalis (L.) Scop.), and the Maquis shrubland was established to assess the impact of both burn treatments. One treatment covered 10 m2. Soil CO2 emissions together with meteorological conditions were measured around midday over 1-year period ; immediately after burn (IAB), 1 months after burn (1MAB), 3MAB, 8MAB, and 12MAB on each treatment. Additionally, vegetation cover (VC), soil moisture (SM), soil temperature (ST), total carbon (TC), total nitrogen (TN), C:N ratio, and soil organic matter (SOM) were determined. UB treatment had lower soil CO2 emissions than both burn treatments, and didn’t vary significantly during the study period (4.19–11.34 kg ha-1 day-1). However, burning slash piles significantly increased soil CO2 emission at HS (35.65 kg ha-1 day-1) IAB, and (26.25 kg ha-1 day-1) 1MAB. Conversely in the context of MS, the significantly highest soil CO2 emissions were noted 8MAB (23.65 kg ha-1 day-1), 1MAB (20.94 kg ha-1 day-1), and IAB (18.56 kg ha-1 day-1), respectively. Overall, soil CO2 emissions were significantly decreased with VC (r=–0.62), and ST (r=– 0.39), and increase with SM (r=0.41). No significant correlation was found between soil CO2 emissions and TN, TC, C:N ratio, and SOM content, which can be explained by ash influx in the soil. It is assumed that relative rapid vegetation regrowth contributed to decreasing soil CO2 emissions at both burn treatments, as the emissions equiponderated after one-year study. Altogether, it can be concluded that MS and HS contribute to atmospheric loading of CO2 emissions, however due to their relatively small burned area, their impact is not notable on the global scale of loadings of greenhouse gasses. Acknowledgments: The work was supported by Croatian science foundation under the project “Influence of Summer Fire on Soil and Water Quality” (IP-2018-01-1645).

pile burning, soil CO2 emission, Mediterranean

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