Runoff and erosion from a rapidly eroding pinyon-juniper hillslope
No abstract available.
Book chapter↗
Geology topics
David W. Davenport
Publications and source records attributed to David W. Davenport.
Viewpoint: Sustainability of piñon-juniper ecosystems - A unifying perspective of soil erosion thresholds
Many pinon-juniper ecosystem in the western U.S. are subject to accelerated erosion while others are undergoing little or no erosion. Controversy has developed over whether invading or encroaching pinon and juniper species are inherently harmful to rangeland ecosystems. We developed a conceptual model of soil erosion in pinon-jumper ecosystems that is consistent with both sides of the controversy and suggests that the diverse perspectives on this issue arise from threshold effects operating under very different site conditions. Soil erosion rate can be viewed as a function of (1) site erosion potential (SEP), determined by climate, geomorphology and soil erodibility; and (2) ground cover. Site erosion potential and cove act synergistically to determine soil erosion rates, as evident even from simple USLE predictions of erosion. In pinon-juniper ecosystem with high SEP, the erosion rate is highly sensitive to ground cover and can cross a threshold so that erosion increases dramatically in response to a small decrease in cover. The sensitivity of erosion rate to SEP and cover can be visualized as a cusp catastrophe surface on which changes may occur rapidly and irreversibly. The mechanisms associated with a rapid shift from low to high erosion rate can be illustrated using percolation theory to incorporate spatial, temporal, and scale-dependent patterns of water storage capacity on a hillslope. Percolation theory demonstrates how hillslope runoff can undergo a threshold response to a minor change in storage capacity. Our conceptual model suggests that pinion and juniper contribute to accelerated erosion only under a limited range of site conditions which, however, may exist over large areas.
Journal of Range Management↗
Runoff and erosion on the Pajarito Plateau: Observations from the field
Sites within the Pajarito Plateau have widespread, if low levels, of surface contamination. The major mechanism by which contaminants are moved and redistributed is surface runoff and associated soil erosion. To better understand the processes involved, we have been making detailed measurements of water and sediment movement at three sites across the plateau, one located in a ponderosa pine forest, one in a stable pinyon-juniper woodland, and one in a rapidly eroding pinyon-juniper woodland. For the ponderosa pine site, both surface runoff (overland flow) and subsurface runoff (interflow) are important. Overland flow can be generated by intense summer rain storms, more gentle frontal storms, or snowmelt while soils are frozen; interflow, although generated mostly by melting snow, can occur any time of the year. For the pinyon-juniper sites, the most important producer of runoff is summer thunderstorms, but at all scales snowmelt runoff can be important as well. The rapidly eroding pinyon juniper site produces more runoff than the stable pinyon-juniper site and hundreds of times more erosion than either the stable pinyon-juniper or the ponderosa site. These long-term studies are providing a better conceptual understanding of runoff and erosion on the Pajarito Plateau and other similar semiarid regions and enabling better assessments of the potential for contaminant transport in these systems.
New Mexico↗