Data from: Quantifying how short-term environmental variation leads to long-term demographic responses to climate change

1. Climate change is expected to alter not only year-to-year variation in climate but also aspects of within-year variation, such as the length of the intervals between rainfall events and the duration of heat waves. Yet we still have a poor understanding of how intra-annual climate variability and individual weather events alter key vital rates (e.g. individual growth, reproduction and survival) that in part determine population dynamics. 2. Traditionally, ecologists have accounted for this variability across long time periods by attempting to correlate annual vital rates with measures of within-year variability (e.g., the coefficient of variation) to match the scale at which demographic data are collected. An alternative to this aggregate approach is to use within-season yet still relatively infrequent censuses in a probabilistic framework to determine the most likely way that vital rates respond to shorter-term variation in the environment, and how these short-term changes cumulatively lead to the observed yearly vital rates. 3. Here, I present an approach for inferring daily responses of vital rates to short-term weather variability, and apply it to understand how five species of summer annual plants in the Chihuahuan Desert will respond to climate change. 4. Vital rate models reveal that species differ in their responses to above- and below-average conditions, but generally fall into two life histories: 1) species that have fast growth on favorable days, but also experience higher mortality on less favorable days, and 2) species that have slower growth in the same conditions but lower mortality. Results show that the expected rainfall changes in the Chihuahuan desert (more late, cool season rainfall and less frequent, more intense rainfall events) could reduce growth and increase mortality of all summer annual plants. 5. Synthesis. My study shows that vital rates can change in response to short-term variability even when the total amount of rainfall and average temperature, common covariates in demographic models, remain constant. Accounting for changes in short-term environmental variation in climate change predictions will likely be important in systems with considerable environmental variation between censuses. The approach I present here can be widely applied to understand how short-term variability and individual weather events will alter organism responses to climate change.1. 气候变化不仅会改变气候的年际变率，还会影响年内变化的诸多特征，例如降雨事件的间隔时长与热浪的持续时间。然而，我们仍不甚明晰年内气候变异性（intra-annual climate variability）与单次天气事件，如何影响决定种群动态的关键生命率（vital rates）——包括个体生长、繁殖与存活等核心维度。 2. 传统上，生态学家为表征长期时间尺度下的此类波动，尝试将年际生命率与年内变异性指标（例如变异系数）相关联，以匹配种群统计数据（demographic data）的采集尺度。而该聚合式研究方法的替代方案，是在概率框架下利用季内但仍相对稀疏的种群普查（censuses）数据，推断生命率对环境短期波动的最可能响应模式，以及这些短期变化如何累积为观测到的年际生命率。 3. 本研究提出一种可用于推断生命率对短期天气波动的逐日响应模式的方法，并将其应用于解析奇瓦瓦沙漠（Chihuahuan Desert）的5种夏季一年生植物（summer annual plants）如何响应气候变化。 4. 生命率模型结果显示，不同物种对高于或低于平均水平的环境条件的响应存在差异，但大体可归为两类生活史对策：其一为在适宜条件下生长速率更快，但在不利条件下死亡率更高的物种；其二为在同等条件下生长速率较慢，但死亡率更低的物种。研究结果表明，奇瓦瓦沙漠预期的降雨格局变化——即晚秋凉季降雨增多，而降雨事件频次减少、强度增大——可能会降低所有夏季一年生植物的生长速率并提高其死亡率。 5. 综合分析。本研究表明，即便种群统计模型中常用的协变量（covariates）——降雨总量与平均温度保持不变，生命率仍可因短期环境波动而发生变化。在普查间隔内环境波动显著的生态系统中，将短期环境变化纳入气候变化预测模型，或将具有重要意义。本文提出的研究方法可被广泛应用，以解析短期环境波动与单次天气事件将如何改变生物对气候变化的响应模式。