Hydrology and Earth System Sciences
www.hydrol-earth-syst-sci.net
1027-5606
1607-7938
11
6
2007
10.5194/hess-11-1717-2007
http://www.hydrol-earth-syst-sci.net/11/1717/2007/
http://www.hydrol-earth-syst-sci.net/11/1717/2007/hess-11-1717-2007.html
http://www.hydrol-earth-syst-sci.net/11/1717/2007/hess-11-1717-2007.pdf
1717
1730
2007-11-01
Eco-geomorphology of banded vegetation patterns in arid and semi-arid regions
P. M. Saco
patricia.saco@newcastle.edu.au
G. R. Willgoose
G. R. Hancock
School of Engineering, The University of Newcastle, Callaghan, New South Wales, 2308, Australia
School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, 2308, Australia
The interaction between vegetation and hydrologic processes is particularly
tight in water-limited environments where a positive-feedback links soil
moisture and vegetation. The vegetation of these systems is commonly
patterned, that is, arranged in a two phase mosaic composed of patches with
high biomass cover interspersed within a low-cover or bare soil component.
These patterns are strongly linked to the redistribution of runoff and
resources from source areas (bare patches) to sink areas (vegetation
patches) and play an important role in controlling erosion.
<br><br>
In this paper, the dynamics of these systems is investigated using a new
modeling framework that couples landform and vegetation evolution,
explicitly accounting for the dynamics of runon-runoff areas. The objective
of this study is to analyze water-limited systems on hillslopes with mild
slopes, in which overland flow occurs predominantly in only one direction
and vegetation displays a banded pattern. Our simulations reproduce bands
that can be either stationary or upstream migrating depending on the
magnitude of the runoff-induced seed dispersal. We also found that
stationary banded systems redistribute sediment so that a stepped
microtopography is developed. The modelling results are the first to
incorporate the effects of runoff redistribution and variable infiltration
rates on the development of both the vegetation patterns and
microtopography. The microtopography for stationary bands is characterized
by bare soil on the lower gradient areas and vegetation on steeper gradients
areas. For the case of migrating vegetation bands the model generates
hillslope profiles with planar topography. The success at generating not
only the observed patterns of vegetation, but also patterns of runoff and
sediment redistribution suggests that the hydrologic and erosion mechanisms
represented in the model are correctly capturing some of the key processes
driving these ecosystems.
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