title: Reliance on shallow soil water in a mixed-hardwood forest in central Pennsylvania.
abstract: 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.
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Katie P
authors.initials: KP
authors.lastname: Gaines
authors.affiliation: Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Jane W
authors.initials: JW
authors.lastname: Stanley
authors.affiliation: USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR 97208, USA.
authors.forename: Frederick C
authors.initials: FC
authors.lastname: Meinzer
authors.affiliation: Department of Botany, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: McCulloh
authors.affiliation: USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR 97208, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Woodruff
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Weile
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Adams
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Henry
authors.initials: H
authors.lastname: Lin
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA dme9@psu.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: Eissenstat
mesh_terms: D065928:Forests; D010414:Pennsylvania; D018517:Plant Roots; D012987:Soil; D014197:Trees / Q000502:physiology*; D014867:Water / Q000378:metabolism*
chemical_list: D012987:Soil; D014867:Water
keywords: Critical Zone Observatory; ecohydrology; ecophysiology; root ecology; rooting depth; sap flux; stable isotopes; tree water use