Effects of livestock grazing on morphology, hydrology and nutrient retention in four riparian/stream ecosystems, New Mexico, USA

Abstract

Land-use practices such as livestock grazing influence the structure and function of riparian/stream ecosystems. In New Mexico, four streams were selected to determine the impact of moderate livestock grazing on morphology, solute transport, and nutrient retention. Each stream contained a reach currently exposed to grazing and an exclosed, ungrazed reach. Channel width/ depth ratios and in-stream standing stock of plant biomass were greater in the grazed reaches. Solute transport was determined by injecting a conservative tracer (NaBr) and applying a one-dimensional transport with inflow and storage (OTIS) model. Grazed reaches exhibited enhanced transient storage, represented by a larger cross-sectional area of storage zone relative to wetted channel area (As/A). The extent of nutrient retention was determined by co-injecting a reactive tracer (NaNO3) with the conservative tracer. Nitrate uptake lengths were shorter in grazed reaches, an indication of more effective nutrient retention. Our results suggest that moderate livestock grazing alters channel structure and vegetation, influencing ecosystem-level processes.

Parent Publication

• Rio Grande ecosystems: linking land, water, and people: Toward a sustainable future for the Middle Rio Grande Basin

Citation

Thibault, James R.; Moyer, Douglas L.; Dahm, Clifford N.; Valett, H. Maurice; Marshall, Michael C. 1999. Effects of livestock grazing on morphology, hydrology and nutrient retention in four riparian/stream ecosystems, New Mexico, USA. In: Finch, Deborah M.; Whitney, Jeffrey C.; Kelly, Jeffrey, F.; Loftin, Samuel R. Rio Grande ecosystems: linking land, water, and people: Toward a sustainable future for the Middle Rio Grande Basin. 1998 June 2-5; Albuquerque, NM. Proc. RMRS-P-7. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 123-128.