Research
 

Tamarix recruitment along the Colorado River: Interactions among flow regime, geomorphology, and life histories

SUSAN MORTENSON, University of Nevada - Reno, Ecology, Evolution and Conservation Biology Program

DR. PETER WEISBERG, Assistant Professor of Landscape Ecology, University of Nevada - Reno, Department of Natural Resources and Environmental Science

DR. LARRY STEVENS, Consulting Ecologist, Grand Canyon Wildlands Council, Inc., Flagstaff, AZ

GIBNEY SIEMION, Grand Canyon Wildlands Council, Inc., Flagstaff, AZ

 
Abstract: In riparian landscapes, the establishment and spread of Tamarix, a non-native, invasive shrub, is intricately tied to hydrogeomorphology. The timing and magnitude of peak flows combined with substrate texture and elevation determine the likelihood of establishment. We aim to incorporate the interaction between hydrology and geomorphic processes into an empirical model that explains Tamarix establishment in unregulated and regulated reaches of the Colorado River. Dendroecological techniques in combination with analyses of historical aerial photography allow us to precisely correlate specific Tamarix establishment events with temporal variation in flow regime and climate, as well as spatially heterogeneous patterns of geomorphic surface types and particle size distribution. Our study was designed to explore the possibility of using flow manipulations to prevent further Tamarix establishment and favor establishment of native species in the Grand Canyon National Park (GCNP). Many researchers have suggested that implementing a “natural flow regime” will restore riparian landscapes and thwart invasion of non-native species in regulated rivers. However, the phenology of Tamarix seems well-suited towards hydrographs that are dominated by spring floods, and observations of high rates of Tamarix invasion on many unregulated tributaries and river reaches (e.g. Colorado River through Cataract Canyon) do not support the natural flow regime paradigm. Preliminary results from GCNP indicate that Tamarix establishment is facilitated by alternating years of high and then low flow, although a background rate of establishment is maintained by a recent, managed flow regime of low daily and seasonal fluctuations. Short duration test floods implemented in 1996, 2000, and 2004 appear not to favor Tamarix establishment. Further analyses from the Grand Canyon and Cataract Canyon should illustrate the relationship between river regulation and invasibility.

 

Funding provided by: The National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, Biology of Weedy and Invasive Species in Agroecosystems Program

Project duration: September, 2006 - August, 2010

 

Presentations:
Mortenson, S.G., P.J. Weisberg, and L.E. Stevens. 2007. A Retrospective Analysis of Tamarix Establishment in the Grand Canyon National Park: Interactions of Life History and Landscapes. Oral Presentation. Ecological Society of America meetings, San Jose, CA. Link

Mortenson, S.G., P.J. Weisberg, and L.E. Stevens. 2006. Hydrogeomorphic factors influencing the establishment and distribution of Tamarix in Grand Canyon National Park. Oral Presentation. Tamarisk Research Conference, Ft. Collins, CO.

Siemion, G. and L.E. Stevens. 2006. Tamarisk flowering and seed release phenology in relation to climate and Colorado River hydrography. Oral Presentation. Tamarisk Research Conference, Ft. Collins, CO.

Weisberg, P.J., L.E. Stevens, S.G. Mortenson, and G. Siemion. 2007. Non-native Tamarix ramosissima recruitment along the Colorado River: Interactions among flow regime and geomorphology. Weed Science Society of America Annual Meeting, USDA/CSREES NRI Project Directors Meeting, 2-6-07, San Antonio, TX .

Manuscripts:

Mortenson, S.G., P.J. Weisberg, and B.E. Ralston. The influence of beaver on plant community invasibility along a regulated river. Submitted to Wetlands.


University of Nevada, Reno
Maintained by: Nathan Bristow