Seasonal variations in moisture use in a piñon–juniper woodland
Seasonal variations in moisture use in a piñon–juniper woodland
复制标题
DOI：
10.1007/s00442-007-0777-0
复制
发表时间：
2007-06
期刊：
影响因子：
2.7
通讯作者：
A. West;K. Hultine;K. Burtch;J. Ehleringer
中科院分区：
文献类型：
--
作者：
A. West;K. Hultine;K. Burtch;J. Ehleringer
在北美山间地区水分有限的环境中，夏季降水可能在干旱地区群落和生态系统的结构和功能中发挥作用。本研究探讨了潜在的依赖夏季降水的两个广泛存在的木本物种在美国西南部，松树edulisEnglmn。（科罗拉多圆柏）和杜松（犹他州圆柏）。edulis和J.osteosperma的水流分布高度暗示了对夏季降雨的不同依赖性。我们假设P. edulis依赖于夏季降水，即使在极端干旱的夏季也能利用夏季降水，而J. osteosperma是不依赖的，使用夏季降水量只有当量高于一些最低阈值。使用液流和稳定同位素方法来评估季节性水源和水分利用效率，我们研究了这两个物种的响应，水分的季节性变化在一个位于北美季风的北方限制附近的网站。树干液流和同位素结果表明，P. edulis对夏季的降雨有反应，而J. osteosperma没有。在夏季降雨事件之后，树干液流密度增加。几天的教育，但不是在J。骨籽同位素证据表明P. edulistook了夏季来源的水分在更大程度上比J.骨籽叶片可溶性碳水化合物碳的天然丰度稳定同位素比值随夏季的增加而增加。edulis，表明同化在较高的水分利用效率，但不变的J。骨籽我们的结果支持了P. edulisandJ. osteospermaare差异敏感的夏季降水，并讨论了潜在的变化与气候变化相关的降水季节性。
In water-limited environments of the intermountain region of North America, summer precipitation may play a role in the structure and function of aridland communities and ecosystems. This study examined the potential reliance on summer precipitation of two widespread, coexisting woody species in the southwestern United States,Pinus edulisEnglmn. (Colorado piñon) andJuniperus osteosperma(Torr) Little (Utah juniper). The current distributions ofP.edulisandJ.osteospermaare highly suggestive of different dependencies on summer rainfall. We hypothesized thatP. eduliswas dependent on summer precipitation, utilizing summer precipitation even during extremely dry summers, whereasJ. osteospermawas not dependent, using summer precipitation only when amounts were above some minimum threshold. Using sap flux and stable isotopic methods to assess seasonal water sources and water use efficiency, we examined the response of these two species to seasonal variations in moisture at a site located near the northern limits of the North American monsoon. Both sap flux and isotopic results indicated thatP. eduliswas responsive to summer rain, whileJ. osteospermawas not. Following summer rain events, sap flux density increased inP. edulisfor several days, but not inJ. osteosperma. Isotopic evidence indicated thatP. edulistook up summer-derived moisture to a greater extent thanJ. osteosperma. Values of the natural abundance stable isotope ratio of carbon of leaf soluble carbohydrates increased over the summer forP. edulis, indicative of assimilation at higher water use efficiency, but were invariant forJ. osteosperma. Our results supported the hypothesis thatP. edulisandJ. osteospermaare differentially sensitive to summer precipitation and are discussed in the light of potential changes in the seasonality of precipitation associated with climate change.