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National Science Foundation (USA) 2008

Vegetative Roughness Controls on Aeolian Sediment Transport

Roughness Aeolian Transport

NATIONAL SCIENCE FOUNDATION

Titre : Vegetative Roughness Controls on Aeolian Sediment Transport

Organismes NSF : Division Of Earth Sciences (EAR)

Durée : September 1, 2008 — August 31, 2013

Description
The type and distribution of vegetation in arid environments play a critical role in controlling the initiation of the wind-driven sediment transport system as well as the magnitude of the flux of sand and dust. Despite this knowledge, the role of natural vegetation is not well accounted for in present regional wind erosion models. Previous research indicates that the change in sand transport rate due to large solid non-erodible roughness elements is a function of both the size and the distribution of the elements. For vegetation its properties (e.g., porosity, flexibility, drag coefficients, distribution, etc.) create uncertainty as to how similar their effects are as compared to solid element roughness, which is typically assumed in current wind erosion models. This project will investigate through field-based experimentation, how plant community structure as characterized by its distribution pattern and associated aerodynamic properties affects sand transport by wind. The data needed to answer these questions will be collected at four sites within the USDA Jornada Experimental Range (JER), NM, where the landscape has changed from one dominated by grasslands to one that is becoming dominated by shrubs, with a resultant increase in wind erosion and land degradation. The four sites represent different stages of mesquite invasion at the JER. At each of the sites instruments will measure regional and local wind speeds, surface shear stresses, sand movement activity, and the vegetation distribution characteristics. This research will aid in the identification of key characteristics of vegetation that can be used to indicate either stability or the approach of a critical threshold that subsequently leads to an increase in wind erosion and environmental degradation. The results from this project will provide a means to more accurately quantify the effect of sparse vegetation on sediment transport thresholds and sand fluxes, which can be incorporated into regional wind erosion models.
This research is designed to increase our understanding of the links between wind-driven sediment transport processes and vegetation in desert environments in general. Desert environments worldwide are under pressure from climate change as well as expanding populations and their need for resources. Vegetation plays a critical role in the stability of desert environments, specifically as a buffer against wind erosion and the often-associated dust emission process. However, as evident in parts of the Chihuahuan desert in the U.S. southwest some desert plant communities, by virtue of their survival mechanisms, can exacerbate wind erosion, leading to environmental decline. Vegetation can therefore both positively and negatively influence wind erosion processes and the results of this project will aid in determining the nature and degree of these influences under a variety of environmental conditions. Such knowledge can subsequently be used to aid in evaluating how climate change and human-induced pressures could exacerbate degradation in these sensitive areas.

Partenaire (s) : Jack Gillies jackg dri.edu (Principal Investigator)

Financement : $300,063.00

Présentation (National Science Foundation)

Page publiée le 6 novembre 2017