Semi-arid landscapes typically consist of patchy vegetation and associated soil heterogeneity. The dynamics of runoff and infiltration have been hypothesized to ecohydrologically link vegetated and un-vegetated areas. We studied small-scale soil heterogeneity and its effect on runoff, infiltration and redistribution of water in two semi-arid shrublands and a grassland landscape. We analyzed heterogeneity of surface soil properties in relation to the vegetation type and pattern, and landforms. Most of the soil properties studied are different under vegetation from the bare-ground intercanopy area. Microtopography and saturated conductivity are almost always higher under plant canopy and decreased with distance away from canopy. The magnitude and scale of spatial variability varies primarily with vegetation type and landform. Geostatistical analysis shows that soil heterogeneity commonly extends 3-4 times the width of plant canopy.
We quantified the effects of microtopography and saturated conductivity variability on runoff in the grassland site. We used runoff observations and a numerical model that couples infiltration and overland flow over detailed maps of heterogeneous soil properties. Microtopography has ∼30 times larger effect than saturated conductivity: omitting microtopography can result in 200% more runoff predicted by the model. The effect of microtopography is due to depression storage, which affects the timing of runoff, hydrograph shape, spatial distribution of overland flow depths, and the location and magnitude of infiltration.
We studied the effects of overland flow on the spatial pattern and magnitude of infiltration, a process dubbed redistribution. Redistribution has been hypothesized to play a key role in the ecohydrologic function of drylands. Redistribution was only detected in alluvial fan shrublands and gently sloping grasslands. Most redistribution occurs near the edges of vegetation canopy rather than underneath. Infiltration of surface water in microtopographic depressions was found to be more important than inundation of more infiltrable plant mounds, even in the case of extreme variations in infiltration capacity.
Soil heterogeneity associated with semi-arid vegetation strongly affects the location and amounts of runoff and infiltration in semi-arid shrublands and grasslands. Microtopography, which is relatively unstudied in dryland ecohydrology, affects runoff, infiltration, and concentration of rainfall more than variability of infiltration capacity at our sites.
|Advisor:||Small, Eric E.|
|Commitee:||Anderson, Robert S., Beatty, Susan W., Miller, David M., Tucker, Greg E.|
|School:||University of Colorado at Boulder|
|School Location:||United States -- Colorado|
|Source:||DAI-B 69/11, Dissertation Abstracts International|
|Subjects:||Ecology, Geography, Geology|
|Keywords:||Grasslands, Infiltration, Overland flow, Plant patterns, Redistribution, Runoff, Semiarid, Shrubland, Soil heterogeneity|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be