Carroll James M, Davis Craig A, Elmore R Dwayne, Fuhlendorf Samuel D
Department of Natural Resource Ecology and Management Oklahoma State University Stillwater OK USA.
Ecol Evol. 2017 Jul 8;7(16):6413-6422. doi: 10.1002/ece3.3185. eCollection 2017 Aug.
Deviations from typical environmental conditions can provide insight into how organisms may respond to future weather extremes predicted by climate modeling. During an episodic and multimonth heat wave event (i.e., ambient temperature up to 43.4°C), we studied the thermal ecology of a ground-dwelling bird species in Western Oklahoma, USA. Specifically, we measured black bulb temperature () and vegetation parameters at northern bobwhite (; hereafter bobwhite) adult and brood locations as well as at stratified random points in the study area. On the hottest days (i.e., ≥39°C), adults and broods obtained thermal refuge using tall woody cover that remained on average up to 16.51°C cooler than random sites on the landscape which reached >57°C. We also found that refuge sites used by bobwhites moderated thermal conditions by more than twofold compared to stratified random sites on the landscape but that commonly exceeded thermal stress thresholds for bobwhites (39°C) for several hours of the day within thermal refuges. The serendipitous high heat conditions captured in our study represent extreme heat for our study region as well as thermal stress for our study species, and subsequently allowed us to assess ground-dwelling bird responses to temperatures that are predicted to become more common in the future. Our findings confirm the critical importance of tall woody cover for moderating temperatures and functioning as important islands of thermal refuge for ground-dwelling birds, especially during extreme heat. However, the potential for extreme heat loads within thermal refuges that we observed (albeit much less extreme than the landscape) indicates that the functionality of tall woody cover to mitigate heat extremes may be increasingly limited in the future, thereby reinforcing predictions that climate change represents a clear and present danger for these species.
与典型环境条件的偏差可以帮助我们了解生物体如何应对气候模型预测的未来极端天气。在美国俄克拉荷马州西部发生的一次持续数月的间歇性热浪事件（即环境温度高达43.4°C）期间，我们研究了一种地栖鸟类的热生态学。具体而言，我们测量了美国北部鹑鸡类（以下简称鹑鸡）成年个体和育雏地点以及研究区域内分层随机点的黑球温度（）和植被参数。在最热的日子（即≥39°C），成年个体和育雏群体利用高大的木质植被获得热庇护，这些植被平均比景观中随机地点凉爽16.51°C，而随机地点温度超过了57°C。我们还发现，与景观中的分层随机地点相比，鹑鸡使用的庇护地点使热条件缓和了两倍多，但在热庇护所内，一天中的几个小时内，通常会超过鹑鸡的热应激阈值（39°C）。我们研究中偶然出现的高温条件代表了我们研究区域的极端高温以及我们研究物种的热应激，随后使我们能够评估地栖鸟类对预计未来会更常见的温度的反应。我们的研究结果证实了高大木质植被对于调节温度以及作为地栖鸟类重要热庇护岛的关键重要性，尤其是在极端高温期间。然而，我们观察到的热庇护所内极端热负荷的可能性（尽管比景观中的极端程度要小得多）表明，高大木质植被减轻极端高温的功能在未来可能会越来越有限，从而强化了气候变化对这些物种构成明显且当前危险的预测。
