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首页> 外文期刊>Environmental research >Wildfire effects on lipid composition and hydrophobicity of bulk soil and soil size fractions under Quercus sober cover (SW-Spain)
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Wildfire effects on lipid composition and hydrophobicity of bulk soil and soil size fractions under Quercus sober cover (SW-Spain)

机译：野火对栎属清醒覆盖下大块土壤脂质组成和疏水性的影响以及土壤粒径分数（SW-西班牙）

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摘要

Soil water repellency (hydrophobicity) prevents water from wetting or infiltrating soils, triggering changes in the ecosystems. Fire may develop, enhance or destroy hydrophobicity in previously wettable or water-repellent soils. Soil water repellency is mostly influenced by the quality and quantity of soil organic matter, particularly the lipid fraction. Here we report the results of a study on the effect of fire on the distribution of soil lipids and their role in the hydrophobicity grade of six particle size fractions (2-1, 1-0.5, 0.5-0.25, 0.25-0.1, 0.1-0.05 and < 0.05 mm) of an Arenosol under Quercus suber canopy at the Donana National Park (SW-Spain). Hydrophobicity was determined using water drop penetration time test. Field emission scanning electron microscopy (FESEM) was used to assess the presence and morphology of the inorganic and organic soil components in the particle size fractions. Soil lipids were Soxhlet extracted with a dichloromethane-methanol mixture. Fatty acids (FAs) and neutral lipids were separated, derivatized, identified and quantified by gas chromatography/mass spectrometry and gas chromatography/flame ionization detection. The hydrophobicity values of soil samples and fractions were statistically different (P < 0.05), for both, the unburnt and burnt soils, and particle size fractions. All samples displayed a similar distribution of FAs, straight-chain saturated acids in the C_(14)-C_(32) range, and neutral lipids (n-alkan-1-ols, n-alkanes), only differing in their relative abundances. Among possible biogeochemical mechanisms responsible for the changes in soil lipids, the observed depletion of long chain FAs (.C_(≥24)) in the coarse fraction is best explained by thermal cracking caused by the heat of the fire. The enrichment of long chain FAs observed in other fractions suggests possible exogenous additions of charred, lipid-rich, material, like cork suberin or other plant-derived macromolecules (cutins). Principal component analysis was used to study the relationships between hydrophobicity with soil organic matter and its different components. Extractable organic matter (EOM) and specifically long chain FAs content were positively correlated to soil hydrophobicity. Therefore, the latter could be used as biomarkers surrogated to hydrophobicity in sandy soils.
机译：土壤憎水性（疏水性）可防止水润湿或渗透土壤，从而触发生态系统的变化。火灾可能会在先前可润湿或憎水的土壤中形成，增强或破坏疏水性。土壤疏水性主要受土壤有机质的质量和数量的影响，尤其是脂质部分。在这里，我们报告了火对土壤脂质分布的影响及其在六个粒度级分（2-1、1-0.5、0.5-0.25、0.25-0.1、0.1-在多纳纳国家公园（西班牙西南部）的Quercus suber冠层下的槟榔（0.05≤0.05 mm）。使用水滴渗透时间测试确定疏水性。场发射扫描电子显微镜（FESEM）用于评估粒度级分中无机和有机土壤成分的存在和形态。用二氯甲烷-甲醇混合物对土壤脂质进行索氏提取。脂肪酸（FAs）和中性脂质通过气相色谱/质谱和气相色谱/火焰离子化检测进行分离，衍生，鉴定和定量。对于未焚烧土壤和焚烧土壤以及粒度级分，土壤样品和级分的疏水性值在统计学上均不同（P <0.05）。所有样品均显示出相似的FA分布，C_（14）-C_（32）范围内的直链饱和酸和中性脂质（正构烷烃1-醇，正构烷烃），但其相对丰度不同。在引起土壤脂质变化的可能的生物地球化学机制中，观察到的粗粒中长链FAs（.C_（≥24））的耗尽最好用火热引起的热裂化来解释。在其他馏分中观察到的长链FA的富集表明，可能是外源添加了烧焦的，富含脂质的物质，例如软木栓木或其他植物衍生的大分子（角质）。主成分分析用于研究疏水性与土壤有机质及其不同成分之间的关​​系。可萃取有机物（EOM），特别是长链脂肪酸的含量与土壤疏水性呈正相关。因此，后者可以用作替代沙质土壤中疏水性的生物标记。

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