Drought events are predicted to increase under future climate change. In temperate ecosystems, plants are capable of resisting drought due to their hydrophobic wax layer, in which n-alkanes are important constituents. In soils, plant-derived n-alkanes are comparatively resistant to degradation. To improve understanding of the significance of n-alkanes in plant-soil systems during a severe drought period (104 days), we investigated bulk organic carbon (Corg) concentration, total lipid extract (TLE) concentration, n-alkane molecular ratios such as average chain length (ACL), carbon preference index (CPI) and chain length ratios of different n-alkane compounds, in addition to the compound-specific isotope composition (δ13C) of n-alkanes in model temperate grassland and heathland plant-soil systems. Although plant communities of two (heathland) and four (grassland) species were available, only one representative species per biome was accessible for the current study. Heathland plants and soil revealed significantly higher concentrations of Corg and TLE compared with grassland. TLE and alkane composition responded quickly during the first drought phase (0 – 40 days). This indicates that plants were actively utilizing C and produced more n-alkanes in order to withstand drought, which was confirmed by increased (2 – 3‰) δ13C values for n-alkanes in shoot biomass. However, during later drought phases all the parameters remained constant for plants and soils. This suggests limited change in biosynthesis and cycling of plant lipids such as n-alkanes during intense drought. Surprisingly, during the first drought phase, increased ACL and CPI ratios in soil demonstrated a rapid input of plant-derived long chain n-alkanes to soil, which was not expected due to the decadal residence time of alkanes in soil. The study enabled tracing of plant metabolic response in terms of alkane biosynthesis under different phases of drought and rapid cycling of alkanes in the plant-soil system.

中文翻译：

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模式温带草原和荒地生态系统中受严重干旱影响的植物和土壤正烷烃的组成和δ 13 C

在未来的气候变化下，预计干旱事件会增加。在温带生态系统中，植物由于其疏水蜡层能够抵抗干旱，其中正构烷烃是重要的成分。在土壤中，植物来源的正构烷烃相对抗降解。为了更好地理解严重干旱期（104 天）植物-土壤系统中正构烷烃的重要性，我们研究了大量有机碳 (Corg) 浓度、总脂质提取物 (TLE) 浓度、正构烷烃分子比，例如不同正烷烃化合物的平均链长 (ACL)、碳偏好指数 (CPI) 和链长比，以及模型温带草原和石南植物土壤系统中正烷烃的化合物特定同位素组成 (δ13C) . 尽管有两种（荒地）和四种（草地）物种的植物群落可用，但当前研究中每个生物群落只能获得一种代表性物种。与草地相比，荒地植物和土壤的 Corg 和 TLE 浓度显着更高。在第一个干旱阶段（0-40 天），TLE 和烷烃成分反应迅速。这表明植物正在积极利用 C 并产生更多的正构烷烃以抵御干旱，这通过芽生物质中正构烷烃的 δ13C 值增加 (2 – 3‰) 得到证实。然而，在后期干旱阶段，植物和土壤的所有参数都保持不变。这表明在严重干旱期间植物脂质（如正烷烃）的生物合成和循环变化有限。令人惊讶的是，在第一个干旱阶段，土壤中 ACL 和 CPI 比率的增加表明植物来源的长链正构烷烃向土壤的快速输入，这是由于烷烃在土壤中的十年停留时间而出乎意料的。该研究能够追踪植物-土壤系统中不同干旱阶段和烷烃快速循环下烷烃生物合成方面的植物代谢反应。