Ehleringer James R
Department of Biology, University of Utah, 84112, Salt Lake City, UT, USA.
Oecologia. 1988 Sep;76(4):553-561. doi: 10.1007/BF00397869.
Encelia farinosa and Encelia frutescens are drought-decidous shrubs whose distributions overlap throughout much of the Sonoran Desert. During hot and dry periods, leaves of E. farinosa utilize increased leaf reflectance to reduce leaf temperature, whereas leaves of E. frutescens have substantially higher leaf conductances and rely on increased transpirational cooling to reduce leaf temperature. E. farinosa is common on the dry slope microhabitats, whereas E. frutescens occurs only in wash microhabitats where greater soil moisture is available to provide the water necessary for transpirational cooling. E. farinosa tends not to persist in wash microhabitats because of its greater susceptibility to flashfloods. The consequences and significance of increased leaf reflectance versus increased transpirational cooling to leaf temperature regulation are discussed.
粉苞菊和灌木粉苞菊是干旱落叶灌木，它们的分布在索诺兰沙漠的大部分地区重叠。在炎热干燥时期，粉苞菊的叶子利用增加的叶片反射率来降低叶温，而灌木粉苞菊的叶子具有更高的叶片导度，并依靠增加蒸腾散热来降低叶温。粉苞菊在干燥的斜坡微生境中很常见，而灌木粉苞菊仅出现在冲刷微生境中，那里有更多的土壤水分可用于提供蒸腾散热所需的水分。由于粉苞菊更容易受到山洪暴发的影响，它往往不会在冲刷微生境中持续存在。本文讨论了增加叶片反射率与增加蒸腾散热对叶温调节的后果和意义。
