Office of Arid Lands Studies, University of Arizona, 1955 E. Sixth St, Tucson, AZ 85721, USA.
Department of Soil, Water and Environmental Science, University of Arizona, PO Box 210038, Tucson, AZ 85721-0038, USA.
New Phytol. 2011 Jul;191(2):468-479. doi: 10.1111/j.1469-8137.2011.03705.x. Epub 2011 Mar 30.
Temperatures for the southwestern USA are predicted to increase in coming decades, especially during the summer season; however, little is known about how summer precipitation patterns may change. We aimed to better understand how nonsucculent plants of a water-limited gradient encompassing xeric desert to mesic mountain-top may respond to changes in summer conditions. We used a species-rich 26-yr flowering record to determine species' relationships with precipitation and temperature in months coincident with and previous to flowering. The onset of summer flowering was strongly influenced by the amount and timing of July precipitation, regardless of elevation or life form, suggesting the critical importance of soil moisture in triggering summer flowering in this region. Future changes in the timing or consistency of the early monsoon will probably impact directly on the onset of flowering for many species in this region. In addition, a key implication of predicted increasing temperatures is a decrease in available soil moisture. At all elevations, many species may be expected to flower later in the summer under the decreased soil moisture conditions associated with warmer temperatures. However, impacts on summer flowering may be greater at higher elevations, because of the greater sensitivity of mesic plants to water stress.
美国西南部的气温预计在未来几十年内会升高，特别是在夏季；然而，对于夏季降水模式可能会如何变化，人们知之甚少。我们旨在更好地了解涵盖干旱沙漠到湿润山顶的水分限制梯度上的非肉质植物将如何应对夏季条件的变化。我们使用了一个 26 年的丰富开花记录，以确定物种与开花同期和之前几个月降水和温度的关系。夏季开花的开始强烈受到 7 月降水的数量和时间的影响，无论海拔或生活型如何，这表明在该地区触发夏季开花的土壤水分的关键重要性。未来早季风的时间或一致性的变化可能会直接影响该地区许多物种的开花开始。此外，预测的温度升高的一个关键影响是可用土壤水分的减少。在所有海拔高度，许多物种的花期可能会因与温暖气温相关的土壤水分减少而延迟到夏季后期。然而，由于对水分胁迫更为敏感，较高海拔地区的夏季开花可能会受到更大的影响。
