Data from: Avian demographic responses to drought and fire: a community-level perspective

Drought stress is an important consideration for wildlife in arid and semi-arid regions under climate change. Drought can impact plant and animal populations directly, through effects on their physiology, as well as indirectly through effects on vegetation productivity and resource availability, and by creating conditions conducive to secondary disturbance, such as wildfire. We implemented a novel approach to understanding community-level demographic responses of birds and their habitats to these stressors in the context of climate change at 14 study sites in the Four Corners region of the southwestern United States. A large wildfire affecting three of the sites provided a natural experiment for also examining fire effects on vegetation and the bird community. We assessed: 1) trends in drought and end-of-century (2071-2100) predicted average drought conditions under mid-range and high greenhouse gas concentration trajectory scenarios; 2) effects of drought and fire on habitat (vegetation greenness); and 3) effects of drought and fire on community-level avian productivity and adult apparent survival rates. Drought has increased and is expected to increase further at our study sites under climate change. Under spring drought conditions, vegetation greenness and avian productivity declined, while summer drought appeared to negatively affect adult apparent survival rates. Response to fire was mixed; in the year of the fire, avian productivity declined, but was higher than normal for several years post-fire. Our results highlight important links between environmental stressors and avian vital rates that will likely affect population trajectories in this region under climate change. We suggest that the use and continued development of community-level demographic models will provide useful tool for leveraging sparse species-level data to provide multi-species inferences and inform conservation.

在气候变化背景下，干旱胁迫（drought stress）是干旱与半干旱地区野生生物需重点考量的环境因素。干旱可通过直接影响动植物的生理过程对其种群产生作用，也可通过改变植被生产力与资源可获得性、营造利于野火等次生干扰（secondary disturbance）发生的环境，间接对种群造成影响。本研究在美国西南部四角地区（Four Corners region）的14个研究样地中，采用创新性方法，解析了气候变化背景下鸟类及其栖息地对这类胁迫因子的群落水平种群统计响应（community-level demographic responses）。其中3个样地受大规模野火影响，这为探究野火对植被与鸟类群落的效应提供了天然实验（natural experiment）场景。本研究评估了三方面内容：1）干旱的变化趋势，以及在中等浓度与高浓度温室气体浓度排放情景（greenhouse gas concentration trajectory scenarios）下，本世纪末（2071-2100年）的预测平均干旱状况；2）干旱与野火对栖息地（植被绿度）的影响；3）干旱与野火对鸟类群落水平繁殖生产力以及成鸟表观存活率（apparent survival rates）的影响。在本研究的样地中，干旱程度已有所加剧，且在气候变化背景下预计将进一步加重。春季干旱条件下，植被绿度与鸟类繁殖生产力均出现下降；而夏季干旱则会对成鸟表观存活率产生负面影响。鸟类群落对野火的响应存在差异：野火发生当年，鸟类繁殖生产力有所下降，但在灾后数年内，该指标均高于正常水平。本研究结果揭示了环境胁迫因子与鸟类生命率（avian vital rates）之间的重要关联，这类关联或在气候变化背景下影响该区域的种群动态轨迹（population trajectories）。我们提出，应用并持续优化群落水平种群统计模型（community-level demographic models），将成为利用稀疏的物种水平数据开展多物种推断（multi-species inferences）、为保护工作提供决策依据的有效工具。