Woody Plant Invasion Changes Soil Water Storage Dynamics And Shifts Runoff Generation Mechanisms

Abstract:

Infiltration excess and saturation excess are the main runoff generation mechanisms for rangeland watersheds, while the role of subsurface stormflow is highly variable. Climate, topography, vegetation, and edaphic factors determine the runoff generation processes for a given location and a substantial change in any of these factors, either alone or combined, could result in a change in soil water storage dynamics and cause a shift in the runoff generation mechanisms.

Three paired experimental watersheds were established in 2010 to quantify the streamflow responses to woody plant invasion into grassland in the South-central Great Plains. Here, we compare the runoff generation mechanisms under both vegetation types using soil water content and surface runoff data from 2011 to 2014. These data were collected every 5-15 minutes during the period experiencing both extremely high and low precipitation events. The objectives of this study include: 1). Understand change in soil moisture content and storage dynamic across the entire soil profile under grassland and woody plant invaded grassland watersheds; 2). Determine the dominant runoff mechanism for each vegetation type; and 3). Illustrate the process which shifts the runoff generation mechanisms. These results are important in understanding the impact of woody plant expansions on altering surface water and groundwater availability and therefore affect water resources sustainability management in the South-central Great Plains.