Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
Centre for Past Climate Change and School of Archaeology, Geography and Environmental Sciences (SAGES), University of Reading, Whiteknights, RG6 6AH Reading, UK.
Science. 2017 Sep 1;357(6354):917-921. doi: 10.1126/science.aal4760.
Leaf size varies by over a 100,000-fold among species worldwide. Although 19th-century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal gradient of leaf size has not been well quantified nor the key climatic drivers convincingly identified. Here, we characterize worldwide patterns in leaf size. Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations. By modeling the balance of leaf energy inputs and outputs, we show that daytime and nighttime leaf-to-air temperature differences are key to geographic gradients in leaf size. This knowledge can enrich "next-generation" vegetation models in which leaf temperature and water use during photosynthesis play key roles.
叶片大小在全球物种间差异超过 10 万倍。尽管 19 世纪的植物地理学家注意到，潮湿热带地区拥有叶片异常大的植物，但叶片大小的纬度梯度尚未得到很好的量化，关键的气候驱动因素也没有得到令人信服的识别。在这里，我们描述了全球范围内叶片大小的模式。大叶片物种在潮湿、炎热、阳光充足的环境中占优势；只有在干旱条件下，小叶片物种才是炎热、阳光充足环境的典型特征；小叶片也存在于高纬度和高海拔地区。通过模拟叶片能量输入和输出的平衡，我们表明白天和夜间的叶片与空气的温差是叶片大小地理梯度的关键。这一知识可以丰富“下一代”植被模型，其中叶片温度和光合作用期间的水分利用起着关键作用。
