Gaines Katie P, Stanley Jane W, Meinzer Frederick C, McCulloh Katherine A, Woodruff David R, Chen Weile, Adams Thomas S, Lin Henry, Eissenstat David M
Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA.
Tree Physiol. 2016 Apr;36(4):444-58. doi: 10.1093/treephys/tpv113. Epub 2015 Nov 6.
We investigated depth of water uptake of trees on shale-derived soils in order to assess the importance of roots over a meter deep as a driver of water use in a central Pennsylvania catchment. This information is not only needed to improve basic understanding of water use in these forests but also to improve descriptions of root function at depth in hydrologic process models. The study took place at the Susquehanna Shale Hills Critical Zone Observatory in central Pennsylvania. We asked two main questions: (i) Do trees in a mixed-hardwood, humid temperate forest in a central Pennsylvania catchment rely on deep roots for water during dry portions of the growing season? (ii) What is the role of tree genus, size, soil depth and hillslope position on the depth of water extraction by trees? Based on multiple lines of evidence, including stable isotope natural abundance, sap flux and soil moisture depletion patterns with depth, the majority of water uptake during the dry part of the growing season occurred, on average, at less than ∼60 cm soil depth throughout the catchment. While there were some trends in depth of water uptake related to genus, tree size and soil depth, water uptake was more uniformly shallow than we expected. Our results suggest that these types of forests may rely considerably on water sources that are quite shallow, even in the drier parts of the growing season.
我们研究了页岩衍生土壤上树木的水分吸收深度，以评估一米多深的根系作为宾夕法尼亚州中部一个集水区水分利用驱动因素的重要性。这些信息不仅是增进对这些森林水分利用基本理解所必需的，也是改进水文过程模型中根系深度功能描述所必需的。该研究在宾夕法尼亚州中部的萨斯奎哈纳页岩山关键带观测站进行。我们提出了两个主要问题：（i）宾夕法尼亚州中部一个集水区的混交硬木湿润温带森林中的树木在生长季节的干旱时期是否依靠深根获取水分？（ii）树木属、大小、土壤深度和山坡位置对树木水分提取深度有何作用？基于包括稳定同位素自然丰度、液流通量和土壤水分随深度的消耗模式等多方面证据，在整个集水区，生长季节干旱期的大部分水分吸收平均发生在土壤深度小于约60厘米处。虽然在水分吸收深度方面存在一些与树木属、大小和土壤深度相关的趋势，但水分吸收比我们预期的更均匀地浅。我们的结果表明，即使在生长季节较干燥的时候，这类森林可能相当依赖很浅的水源。
