Data from: The utility of climatic water balance for ecological inference depends on vegetation physiology assumptions

This repository contains the data and code supporting the analyses in the corresponding paper in Global Ecology and Biogeography (GEB). The abstract of the paper is as follows: Background: In modeling and explaining spatial vegetation patterns, ecologists have increasingly favored the use of climatic water balance variables, including actual evapotranspiration (AET) and climatic water deficit (CWD), for representing the hydrologic and energetic environment experienced by plants. Much of the interest in these variables lies in their hypothesized potential to characterize biologically relevant environmental variation more directly than simple climate variables such as precipitation and temperature. Practically, obtaining AET and CWD values across space requires hydrologic process models that involve assumptions, including assumptions about vegetation transpiration rates. However, transpiration parameter values are rarely known with precision and can vary several-fold within and among vegetation types. Approach: We evaluate the extent to which assumptions about vegetation physiology in water balance models affect (a) relative spatial variation in modeled water balance values and (b) ecological inferences that are derived from analyses using water balance variables. We demonstrate an approach for identifying inferences that are robust to these assumptions. Results: Assumptions about vegetation physiology can substantially affect relative spatial variation in modeled water balance values. More importantly, such assumptions can also substantially affect the inferences (e.g., expected vegetation distributions) drawn from ecological analyses that employ water balance variables. Water balance variables are less sensitive to assumptions in environmental settings with abundant water supply, where AET variation is driven primarily by available energy (e.g., temperature and insolation), but they can be highly sensitive to assumptions in drier environments. Conclusion: Because of their sensitivity to assumptions, water balance variables are not unambiguously superior to simpler climate and topographic variables such as precipitation and temperature. However, they retain some advantages, primarily related to their mechanistic incorporation of interactions between water and energy, which may support their use in applications where sensitivity to hydrological modeling assumptions is low or of minor concern.本代码仓库包含支持发表于《全球生态学与生物地理学》（Global Ecology and Biogeography，缩写GEB）期刊对应论文的分析所用数据与代码。该论文的摘要如下： 背景：在建模与阐释空间植被格局的过程中，生态学家愈发倾向于采用气候水文平衡变量——包括实际蒸散量（actual evapotranspiration, AET）与气候水文亏缺（climatic water deficit, CWD）——来表征植物所处的水文与能量环境。相较于降水、气温这类基础气候变量，此类变量被认为能够更直接地刻画与生物过程相关的环境变异，这也是其广受关注的核心缘由。在实际操作中，获取全域范围内的AET与CWD数值需要借助水文过程模型，而这类模型往往包含诸多假设，其中就涵盖植被蒸腾速率相关的设定。然而，蒸腾参数的精准取值往往难以确定，且在不同植被类型内部及类群间，其取值差异可达数倍之多。 研究方法：本研究旨在评估水文平衡模型中的植被生理学假设，会在多大程度上影响（a）建模所得水文平衡变量的相对空间变异，以及（b）基于该类变量开展分析所推导出的生态学推论。同时，本文还提出了一种可识别不受此类假设影响的稳健推论的分析方法。 研究结果：植被生理学相关假设会显著改变建模所得水文平衡变量的相对空间变异。更为重要的是，这类假设还会极大影响通过水文平衡变量开展生态学分析所得到的推论（例如预期植被分布格局）。在水资源充足的环境中，实际蒸散量的变异主要由可利用能量（如气温与日照辐射）驱动，因此水文平衡变量对相关假设的敏感度较低；但在干旱环境中，这类变量对假设的敏感度会显著升高。 研究结论：鉴于水文平衡变量对建模假设存在敏感性，其并非绝对优于降水、气温这类基础气候变量以及地形变量。不过，这类变量仍具备一定优势，主要体现在其能够从机理层面整合水热交互作用，因此在对水文模型假设的敏感性要求较低或无需重点考量该因素的应用场景中，仍可考虑采用。