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Quantifying the Sensitivity of Land-Surface Models to Hydrodynamic Stress Limitations on Transpiration

Matheny, Ashley Michelle
http://orcid.org/0000-0002-9532-7131
http://rave.ohiolink.edu/etdc/view?acc_num=osu1364572098

Abstract Details

2013, Master of Science, Ohio State University, Civil Engineering.
Evapotranspiration is a major forcing function of Earth's climate, providing the link for the soil-plant-atmosphere continuum. Stomata conductance, which governs transpiration, also provides the link between latent heat flux and carbon uptake rates. Current land-surface models couple stomata conductance and soil moisture through empirical relationships. This approach does not take advantage of recent advances in our understanding of water flow and storage in trees or of tree and canopy structure. The lack of mechanistic representation of the tree-hydrodynamic process should therefore lead to typical intra-daily patterns of error in results of current models. We use a comparison between observational data and model outputs to characterize the patterns of intra-daily error in simulated water flux. Through the use of the North American Carbon Program (NACP) dataset, more than 10 years of water flux data for 25 Fluxnet sites has been analyzed. The diurnal pattern of latent heat flux error from each of the 10 land-surface models represented in this study allows for categorization and evaluation based on models’ ability to predict the fast temporal dynamics of transpiration in different ecosystems and atmospheric forcing. Distinct error patterns occur when soil moisture is non-limiting, when the soil is near the wilting point, when VPD is not limiting, and when VPD is high. Although model error patterns are site specific, there are models that are more likely to favor one pattern above the other based on the stomata conductance scheme used and its sensitivity to VPD and soil moisture. We contrast these error patterns with sap flux, soil moisture, and leaf water potential measurements conducted in a Northern forest at the University of Michigan Biological Station (UMBS) in Pellston, MI, one of the Fluxnet sites included in the NACP analysis. The co-analysis of the physical process of water transport in the UMBS forest with the errors in model simulated latent heat flux reveals that model error is largest and most variable when moisture conditions are moderate to limiting and vegetative dynamics dominate. We find that models do best when moisture conditions are non-limiting, but have trouble resolving the fast dynamics of transpiration.
Gil Bohrer, PhD (Advisor)
Gajan Sivandran, PhD (Committee Member)
Peter Curtis, PhD (Committee Member)
89 p.
Civil Engineering; Environmental Engineering; Environmental Science
Transpiration; Land Surface Modeling; Sap Flux; UMBS; Hydrodynamic Stress

Recommended Citations

Citations

  • Matheny, A. M. (2013). Quantifying the Sensitivity of Land-Surface Models to Hydrodynamic Stress Limitations on Transpiration [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364572098

    APA Style (7th edition)

  • Matheny, Ashley. Quantifying the Sensitivity of Land-Surface Models to Hydrodynamic Stress Limitations on Transpiration. 2013. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1364572098.

    MLA Style (8th edition)

  • Matheny, Ashley. "Quantifying the Sensitivity of Land-Surface Models to Hydrodynamic Stress Limitations on Transpiration." Master's thesis, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364572098

    Chicago Manual of Style (17th edition)

osu1364572098
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© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.