School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
Tree Physiol. 2011 Jun;31(6):649-58. doi: 10.1093/treephys/tpr052. Epub 2011 Jul 8.
Although hydraulic redistribution has been observed for a range of tree species, including Eucalyptus kochii subsp. borealis (C. Gardner) D. Nicolle, there is limited direct evidence that water taken up by deep roots in moist soil is in fact exuded by shallow roots in dry soil. This paper reports an experiment designed to test this hypothesis. Water enriched with deuterium was added to the groundwater via a slotted tube at 4.5 m depth below 5-year-old E. kochii subsp. borealis trees. Nocturnal sap flow increased markedly immediately after deep irrigation, indicating that the trees were using water from this depth. Two weeks later, samples of surface soil and xylem water were found to contain levels of deuterium up to 30% higher than soils and xylem water from a control plot upslope of the main treatment plot. This is strong evidence that trees used groundwater and that efflux of important amounts of hydraulically redistributed water occurred via the roots of E. kochii subsp. borealis.
尽管已经观察到包括桉树亚种。 borealis（C. Gardner）D. Nicolle 在内的一系列树种存在水力再分配现象，但实际上，深层土壤中根系吸收的水分是由浅层土壤中的根系渗出的，这方面的直接证据有限。本文报告了一项旨在检验这一假设的实验。通过在 5 年生桉树亚种。 borealis 树下 4.5 米深的开槽管将富含氘的水添加到地下水。夜间蒸腾流在深灌后立即显著增加，表明树木正在使用该深度的水。两周后，发现表层土壤和木质部水中的氘含量比主处理区上坡的对照样地的土壤和木质部水高 30%，这有力地证明了树木使用了地下水，并且通过桉树亚种。 borealis 的根系渗出了大量重要的水力再分配水。
