Determining water use by trees and forests from isotopic, energy balance and transpiration analyses: the roles of tree size and hydraulic lift.

Use of soil water and groundwater by open-grown Acer saccharum Marsh. (sugar maple) tree canopies and forests was estimated by measuring transpiration (E) rates using porometry, sap flow methods, and the Bowen ratio method. The Bowen ratio and sap flow methods showed the best agreement; porometer measurements scaled to whole canopies always underestimated E by 15-50%. Trees of different sizes showed very different rates of E. I hypothesized that these differences were due to the differential access of large and small trees to groundwater and soil water, respectively. Transpirational flux was partitioned between soil water and groundwater by tracing the water sources based on their hydrogen stable isotopic composition (deltaD). Soil water deltaD varied between -41 and -16 per thousand seasonally (May to September), whereas groundwater deltaD was -79 +/- 5 per thousand during the entire growing season. Daily transpiration rates of large (9-14 m tall) trees were significantly higher than those of small (3-5 m tall) trees (2.46-6.99 +/- 1.02-2.50 versus 0.69-1.80 +/- 0.39-0.67 mm day(-1)). Small trees also showed greater variation in E during the growing season than large trees. In addition, compared to the large trees, small trees demonstrated greater sensitivity to environmental factors that influence E, such as soil water deficits and increased evaporative demand. Over the entire growing season, large trees and forest stands composed of trees > 10 m tall transpired only groundwater. The high rates of water loss from large trees and older forests were likely a result of the influence of an enhanced "pool" of transpirational water in the upper soil layers caused by hydraulic lift (see Dawson 1993b). The hydraulically lifted water reservoir enabled large trees to use more potential transpirational water during daylight hours than small trees, leading to a greater total water flux. In contrast, small trees and forest stands composed of younger trees almost exclusively used soil water, except during two dry periods when their transpirational water was composed of between 7 and 17% groundwater. Thus groundwater discharge from sugar maple trees and forest stands of different sizes (ages) differs significantly, and large trees and older forest stands have a greater impact on the hydrologic balance of groundwater than small trees and younger forest stands. However, mixed stands (small and large trees) may have a greater overall impact on the regional hydrologic balance than old stands, because trees in mixed stands draw on both soil water and groundwater reservoirs and thus can substantially increase total water discharge on scales from tens to hundreds of hectares.

[1]  C. Field,et al.  Scaling Physiological Processes: Leaf to Globe , 1995 .

[2]  D. Hollinger,et al.  Coupling of tree transpiration to atmospheric turbulence , 1994, Nature.

[3]  R. Ceulemans,et al.  Water flux in a hybrid poplar stand. , 1994, Tree physiology.

[4]  M. Karkal.  Population, environment and development. , 1994, Health for the millions.

[5]  P. Farrington,et al.  Water use of plantation Eucalyptus camaldulensis estimated by groundwater hydrograph separation techniques and heat pulse method , 1994 .

[6]  Melvin T. Tyree,et al.  Hydraulic architecture of Acer saccharum and A. rubrum: comparison of branches to whole trees and the contribution of leaves to hydraulic resistance , 1994 .

[7]  Peter J. Thorburn,et al.  Combining measurements of transpiration and stable isotopes of water to determine groundwater discharge from forests , 1993 .

[8]  P. Marks,et al.  Two hundred years of forest cover changes in Tompkins County, New York' , 1993 .

[9]  J. Ehleringer,et al.  Isotopic enrichment of water in the “woody” tissues of plants: Implications for plant water source, water uptake, and other studies which use the stable isotopic composition of cellulose , 1993 .

[10]  Gail E. Bingham,et al.  Comparison of the Bowen ratio-energy balance and the water balance methods for the measurement of evapotranspiration , 1993 .

[11]  G. Goldstein,et al.  Stomatal and environmental control of transpiration in a lowland tropical forest tree , 1993 .

[12]  J. Ehleringer,et al.  Gender‐Specific Physiology, Carbon Isotope Discrimination, and Habitat Distribution in Boxelder, Acer Negundo , 1993 .

[13]  T. Dawson.  Water sources of plants as determined from xylem-water isotopic composition: perspectives on plant competition, distribution, and water relations. , 1993 .

[14]  Dennis D. Baldocchi,et al.  5 – Scaling Water Vapor and Carbon Dioxide Exchange from Leaves to a Canopy: Rules and Tools , 1993 .

[15]  G. Lin,et al.  Hydrogen Isotopic Fractionation by Plant Roots during Water Uptake in Coastal Wetland Plants , 1993 .

[16]  I. Calder,et al.  Growth and water use of forest plantations , 1992 .

[17]  James R. Ehleringer,et al.  Water uptake by plants: perspectives from stable isotope composition , 1992 .

[18]  Esmaiel Malek,et al.  Night-time evapotranspiration vs. daytime and 24h evapotranspiration , 1992 .

[19]  Lawrence B. Flanagan,et al.  Differential uptake of summer precipitation among co‐occurring trees and shrubs in a pinyon‐juniper woodland , 1992 .

[20]  C. Walker,et al.  The use of stable isotopes of water in characterising the source of water in vegetation , 1991 .

[21]  R. Valentini,et al.  An experimental test of the eddy correlation technique over a Mediterranean macchia canopy , 1991 .

[22]  David Whitehead,et al.  Models of water flux through forest stands: critical leaf and stand parameters. , 1991, Tree physiology.

[23]  J. Lassoie,et al.  Techniques and approaches in forest tree ecophysiology , 1991 .

[24]  James R. Ehleringer,et al.  Streamside trees that do not use stream water , 1991, Nature.

[25]  Robert A. Vertessy,et al.  Transpiration of plantation pinus radiata estimated by the heat pulse method and the bowen ratio , 1990 .

[26]  Philippe H. Martin.  The significance of radiative coupling between vegetation and the atmosphere , 1989 .

[27]  Robert W. Pearcy,et al.  Measurement of transpiration and leaf conductance , 1989 .

[28]  Brent Clothier,et al.  Water Use of Kiwifruit Vines and Apple Trees by the Heat-Pulse Technique , 1988 .

[29]  Paul G. Risser,et al.  The Human Impact on the Natural Environment , 2018 .

[30]  K. G. McNaughton,et al.  Stomatal Control of Transpiration: Scaling Up from Leaf to Region , 1986 .

[31]  P. Jarvis,et al.  CHAPTER 1 – PREDICTING EFFECTS OF VEGETATION CHANGES ON TRANSPIRATION AND EVAPORATION , 1983 .

[32]  G. B. Allison,et al.  The distribution of deuterium and 18O in dry soils: 1. Theory , 1983 .

[33]  R. H. Swanson,et al.  A Numerical Analysis of Heat Pulse Velocity Theory and Practice , 1981 .

[34]  J. Gat.  Chapter 1 – THE ISOTOPES OF HYDROGEN AND OXYGEN IN PRECIPITATION , 1980 .

[35]  T. A. Black,et al.  Psychrometric apparatus for Bowen-ratio determination over forests , 1971 .

[36]  G. Bange,et al.  ON THE QUANTITATIVE EXPLANATION OF STOMATAL TRANSPIRATION , 1953 .