Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Jean-Christophe Domec; Ge Sun; Asko Noormets; Michael J. Gavazzi; Emrys A. Treasure; Erika Cohen; Jennifer J. Swenson; Steve G. McNulty; John S. King
    Date: 2012
    Source: Forest Science 58(5):497-512
    Publication Series: Scientific Journal (JRNL)
    Station: Southern Research Station
    PDF: Download Publication  (3.68 MB)

    Description

    Increasing variability of rainfall patterns requires detailed understanding of the pathways of water loss from ecosystems to optimize carbon uptake and management choices. In the current study we characterized the usability of three alternative methods of different rigor for quantifying stand-level evapotranspiration (ET), partitioned ET into tree transpiration (T), understory transpiration, interception, and soil evaporation (ES) and determined their sensitivity to drought, and evaluated the reliability of soil moisture measurements by taking into account deep soil moisture dynamic. The analyses were conducted in an early- and in a mid-rotation stand of loblolly pine, the predominant species of southern US forest plantations. The three alternative methods for estimating ET were the eddy covariance measurements of water vapor fluxes (ETEC), the water table fluctuation (ETWT), and the soil moisture fluctuation (ETSM). On annual and monthly scales, the three methods agreed to within 10-20%, whereas on a daily scale, the values of ETSM and ETEC differed by up to 50% and ETSM and ETWT differed by up to 100%. The differences between the methods were attributed to root water extraction below measurement depth and to the sampling at different spatial scales. Regardless of the method used, ET at the early-rotation site was 15-30% lower than that at the mid-rotation site. The dry years did not affect ET at the mid-rotation site but reduced significantly ET at the early-rotation site. Soil moisture trends revealed the importance of measuring water content at several depths throughout the rooting zone because less than 20% of the water is stored in the top 30 cm of soil. Annually, ES represented approximately 9 and 14% of ETEC at the mid-rotation site and the early-rotation site, respectively. At the mid-rotation site, T accounted for approximately 70% of ETEC. Canopy interception was estimated to be 5-10% of annual precipitation and 6-13% of total ETEC. At the early-rotation site, T accounted for only 35% of ETEC. At this site, transpiration from subdominant trees and shrubs represented 40-45% of ETEC, indicating that understory was a significant part of the water budget. We concluded that the eddy covariance method is best for estimating ET at the fine temporal scale (i.e., daily), but other soil moisture and water table-based methods were equally reliable and cost-effective for quantifying seasonal ET dynamics.

    Publication Notes

    • You may send email to pubrequest@fs.fed.us to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Domec, Jean-Christophe; Sun, Ge; Noormets, Asko; Gavazzi, Michael J.; Treasure, Emrys A.; Cohen, Erika; Swenson, Jennifer J.; McNulty, Steve G.; King, John S. 2012. A comparison of three methods to estimate evapotranspiration in two contrasting loblolly pine plantations: age-related changes in water use and drought sensitivity of evapotranspiration components. Forest Science 58(5):497-512.

    Keywords

    eddy covariance, loblolly pine, Pinus taeda, sapflow, soil moisture probes, water table

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page
https://www.fs.usda.gov/treesearch/pubs/42288