Plant waxes, including n-alkanes, are commonly used for a wide range of paleo-applications. Several common traits of n-alkanes that are used as paleo-proxies include chain length distribution and average chain length (ACL), as well as plant wax carbon and hydrogen isotopic compositions. The effect of climate on plant wax traits has been the subject of many studies, but a common challenge with modern calibrations is disentangling the effects of species (genetic), temperature, and precipitation from one another. Here, we explore the effect of temperature and drought, independently and combined, on plant wax composition of the species Juniper monosperma in a large ecosystem-scale field manipulation experiment. We find that n-alkane concentrations significantly increase with temperature, but other parameters (including ACL) are not affected. These results support physiological studies that identify n-alkanes as an important barrier to water loss within the plant cuticle. Combined with prior studies, it appears that changes in ACL within sediments are likely controlled by changes in species composition rather than directly by changes in climate. We find little variation in the carbon isotopic composition (δ¹³C) of n-alkanes across the treatments whereas bulk leaf δ¹³C values are higher in the heat and drought treatment. Because leaf δ¹³C values represent a weighted C assimilation signal, these values reflect differences in leaf gas exchange among treatments, whereas the n-alkanes are synthesized when water availability is higher and differences among treatments are not significant enough to influence their values. These results have important implications for using n-alkane traits, including ACL and δ¹³C values, for paleoenvironmental reconstructions.

植物蜡，包括正烷烃，通常用于广泛的古环境应用中。用作古代理的正构烷烃的几个常见特征包括链长分布和平均链长（ACL）以及植物蜡碳和氢同位素组成。气候对植物蜡性状的影响一直是许多研究的主题，但是现代标定的一个共同挑战是使物种（遗传），温度和降水的影响相互区分。在这里，我们在一个大型的生态系统规模的田间试验中，探索了温度和干旱的独立影响和干旱影响，对杜松单子叶植物蜡组成的影响。我们发现，ñ-烷烃浓度随温度显着增加，但其他参数（包括ACL）不受影响。这些结果支持生理学研究，确定正构烷烃是植物表皮失水的重要障碍。结合先前的研究，似乎沉积物中ACL的变化很可能由物种组成的变化控制，而不是直接由气候变化控制。我们发现在碳同位素组成几乎没有变化（δ ¹³ C）的Ñ横跨治疗而散装叶烷烃δ ^13个C值都在热和干旱处理更高。由于叶δ ¹³C值代表加权的C同化信号，这些值反映了处理之间的叶片气体交换差异，而当水的利用率较高且处理之间的差异不足以影响其值时，会合成正构烷烃。这些结果对使用具有重要意义ñ烷烃特征，包括ACL和δ ^13个C值，为古环境重建。