Journal cover Journal topic
Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 2.649 IF 2.649
  • IF 5-year<br/> value: 2.688 IF 5-year
    2.688
  • CiteScore<br/> value: 2.64 CiteScore
    2.64
  • SNIP value: 0.628 SNIP 0.628
  • SJR value: indexed SJR
    indexed
  • IPP value: 1.689 IPP 1.689
  • h5-index value: 6 h5-index 6
Earth Surf. Dynam., 4, 471-488, 2016
https://doi.org/10.5194/esurf-4-471-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
22 Jun 2016
The influence of Holocene vegetation changes on topography and erosion rates: a case study at Walnut Gulch Experimental Watershed, Arizona
Jon D. Pelletier1, Mary H. Nichols2, and Mark A. Nearing2 1Department of Geosciences, University of Arizona, Gould-Simpson Building, 1040 East Fourth Street, Tucson, Arizona 85721-0077, USA
2USDA Southwest Watershed Research Center, 2000 East Allen Rd., Tucson, Arizona 85719, USA
Abstract. Quantifying how landscapes have responded and will respond to vegetation changes is an essential goal of geomorphology. The Walnut Gulch Experimental Watershed (WGEW) offers a unique opportunity to quantify the impact of vegetation changes on landscape evolution over geologic timescales. The WGEW is dominated by grasslands at high elevations and shrublands at low elevations. Paleovegetation data suggest that portions of WGEW higher than approximately 1430 m a.s.l. have been grasslands and/or woodlands throughout the late Quaternary, while elevations lower than 1430 m a.s.l. changed from a grassland/woodland to a shrubland ca. 2–4 ka. Elevations below 1430 m a.s.l. have decadal timescale erosion rates approximately 10 times higher, drainage densities approximately 3 times higher, and hillslope-scale relief approximately 3 times lower than elevations above 1430 m. We leverage the abundant geomorphic data collected at WGEW over the past several decades to calibrate a mathematical model that predicts the equilibrium drainage density in shrublands and grasslands/woodlands at WGEW. We use this model to test the hypothesis that the difference in drainage density between the shrublands and grassland/woodlands at WGEW is partly the result of a late Holocene vegetation change in the lower elevations of WGEW, using the upper elevations as a control. Model predictions for the increase in drainage density associated with the shift from grasslands/woodlands to shrublands are consistent with measured values. Using modern erosion rates and the magnitude of relief reduction associated with the transition from grasslands/woodlands to shrublands, we estimate the timing of the grassland-to-shrubland transition in the lower elevations of WGEW to be approximately 3 ka, i.e., broadly consistent with paleovegetation studies. Our results provide support for the hypothesis that common vegetation changes in semi-arid environments (e.g., from grassland to shrubland) can change erosion rates by more than an order of magnitude, with important consequences for landscape morphology.

Citation: Pelletier, J. D., Nichols, M. H., and Nearing, M. A.: The influence of Holocene vegetation changes on topography and erosion rates: a case study at Walnut Gulch Experimental Watershed, Arizona, Earth Surf. Dynam., 4, 471-488, https://doi.org/10.5194/esurf-4-471-2016, 2016.
Publications Copernicus
Download
Short summary
This paper documents that a shift from grassland to shrubland within the past few thousand years has caused erosion rates to increase more than 10-fold and drainage density to increase approximately 3-fold in areas of otherwise similar climate and geology at a study site in Arizona. We provide a mathematical model that predicts the observed drainage density under both grassland and shrubland conditions. In the model application we are able to tightly constrain every parameter.
This paper documents that a shift from grassland to shrubland within the past few thousand years...
Share