Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, 06511, USA.
Ecology. 2018 Jan;99(1):13-20. doi: 10.1002/ecy.2062. Epub 2017 Dec 4.
Ecological analyses of climate warming explore how rising mean temperature will affect the species composition of communities and their associated functioning. Experimentation usually presumes that warming arises from simultaneous increase in daily maximum (daytime) and minimum (nighttime) temperatures. Yet evidence shows that mean warming arises largely from increasing nighttime temperatures. We report on a 3-yr experiment that compared the effects of daytime and nighttime warming on a community comprising herbaceous plants, grasshopper herbivores and predatory spiders. We warmed experimental mesocosms 3-4°C above ambient control treatments during the daytime (06:00-18:00 h) or nighttime (18:00-06:00 h). Daytime warming caused spiders to seek a thermal refuge low in the plant canopy and away from grasshopper prey, which allowed grasshoppers to spend more time feeding on a competitively dominant plant species. Nighttime had the opposite effect, where spider activity increased causing grasshoppers to reduce feeding. Two consecutive years of daytime warming resulted in a suppression of the competitive dominant plant and increased the diversity and evenness of the plant community, whereas nighttime warming had opposite effects. These results show that ignoring the nuanced effects of asymmetrical warming may lead to inaccurate conclusions about the net effects of climate change on ecosystems.
生态分析探讨了气温升高将如何影响群落的物种组成及其相关功能。实验通常假定变暖是由于日最高温和日最低温的同时升高引起的。然而，有证据表明，平均变暖主要是由于夜间温度的升高。我们报告了一项为期 3 年的实验，该实验比较了日间和夜间升温对由草本植物、草食性蝗虫和捕食性蜘蛛组成的群落的影响。我们在实验性中尺度环境中，将日间（06:00-18:00 h）或夜间（18:00-06:00 h）的环境温度比环境对照处理升高 3-4°C。日间升温导致蜘蛛在植物冠层下部和远离蝗虫猎物的地方寻找热避难所，这使得蝗虫有更多的时间以一种具有竞争优势的植物物种为食。夜间则产生相反的效果，蜘蛛活动增加导致蝗虫减少进食。连续两年的日间升温导致竞争优势植物受到抑制，增加了植物群落的多样性和平坦度，而夜间升温则产生相反的效果。这些结果表明，忽略非对称变暖的细微影响可能导致对气候变化对生态系统的净影响的不准确结论。
