Document: CRA-3-65-45

Dynamic microtopography in a rapidly eroding landscape: Ecological implications.

WILCOX, B.P.* ¹, C.D.ALLEN ² and D.D.BRESHEARS ³

Inter-American Institute for Global Change Research, San Jose dos Campos, Brazil ¹
U.S. Geological Survey, Jemez Mts. Field Station, Los Alamos, NM 87544 USA ²
Los Alamos National Laboratory, Los Alamos, NM 87544 USA ³

Abstract:
Patterns of erosion and land surface stability in semiarid ecosystems are strongly modulated by geomorphic, vegetative, and climatic conditions, yet few models or field studies address these patterns of variability at multiple scales. In the early 1990s we began detailed long-term studies of runoff, erosion, and sediment yield in semiarid pinyon-juniper woodlands of northern New Mexico that show extreme variability in patterns of erosion and microtopographic change through time and space. At some sites hillslope surface conditions are quite dynamic, with multiple inter-annual reversals between aggradation and degradation, combined with seasonal freeze-thaw fluffing of exposed soils, observed at spatial scales ranging from 1 m² plots to multi-hectare watersheds. Erosion patterns and rates vary markedly through time, at scales from individual storm events to years, confirming the importance of conducting high-resolution, long-term studies. Rapidly eroding watersheds have passed ecological thresholds, where the dynamic microtopography presents unstable, degraded conditions that constrain the establishment of herbaceous plants, thereby precluding ecosystem stabilization. Improved understanding of the tight linkages between ecological, hydrological, and geomorphological processes, such as those documented here, is required to address environmental issues related to land use and climate change.

Keywords:

This abstract is being presented at: 10:30 AM in session:
Poster Session #5: Landscape Ecology.