Patrick Shafroth, PhD
Patrick B. Shafroth is a Research Ecologist at the Fort Collins Science Center.
Since 1991, Dr. Shafroth has conducted research on riparian ecosystems, primarily in arid and semi-arid regions of western U.S. He and his colleagues from the USGS and other institutions have focused their work on understanding relationships between surface and ground-water hydrology, fluvial processes, and the dynamics of native and introduced riparian vegetation. This research has often been conducted in the applied context of riparian ecosystem restoration with the goal of providing solid, objective scientific information that can be used to inform riparian restoration efforts. More specific restoration-related research areas include studies of large-scale flow experiments, dam removal, effects of invasive species control and associated restoration actions, and potential interactions with climate change.
Some of Dr. Shafroth’s current research includes studies of: vegetation and geomorphic responses to experimental flow releases downstream of dams on the Bill Williams River, Arizona; the Colorado River delta in Mexico and the U.S.; and the the Colorado River in Grand Canyon; vegetation and geomorphic responses to dam removal on the Elwha River, Washington, where the world's largest dam removals occurred recently; dynamics of non-native riparian plants along western rivers, including patterns of riparian vegetation recovery associated with biological control of Tamarix.
Education and Certifications
Ph.D. in Plant Biology, Arizona State University, 1999
M.S. in Forest Ecology, Colorado State University, 1993
B.A. in Environmental Studies and Geography, University of California, Santa Barbara, 1989
Science and Products
Rethinking avian response to Tamarix on the lower Colorado River: A threshold hypothesis
Altered stream-flow regimes and invasive plant species: The Tamarix case
Early vegetation development on an exposed reservoir: Implications for dam removal
Defining ecosystem flow requirements for the Bill Williams River, Arizona
Tamarisk control, water salvage, and wildlife habitat restoration along rivers in the western United States
Tamarisk research priorities of land and water managers: results from a USGS partnership meeting
Control of Tamarix in the western United States: Implications for water salvage, wildlife use, and riparian restoration
Dating floodplain sediments using tree-ring response to burial
Dominance of non-native riparian trees in western USA
Hybridization of Tamarix ramosissima and T. chinensis (saltcedars) with T. aphylla (athel) (tamaricaceae) in the southwestern USA dertermined from DNA sequence data
Tamarisk tensions
Vegetation responses to dam removal
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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Rethinking avian response to Tamarix on the lower Colorado River: A threshold hypothesis
Many of the world's large river systems have been greatly altered in the past century due to river regulation, agriculture, and invasion of introduced Tamarix spp. (saltcedar, tamarisk). These riverine ecosystems are known to provide important habitat for avian communities, but information on responses of birds to differing levels of Tamarix is not known. Past research on birds along the ColoradoAuthorsCharles van Riper, K.L. Paxton, C. O'brien, P.B. Shafroth, L.J. McGrathAltered stream-flow regimes and invasive plant species: The Tamarix case
Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and SaAuthorsJ.C. Stromberg, S.J. Lite, R. Marler, C. Paradzick, P.B. Shafroth, D. Shorrock, J. M. White, M.S. WhiteEarly vegetation development on an exposed reservoir: Implications for dam removal
The 4-year drawdown of Horsetooth Reservoir, Colorado, for dam maintenance, provides a case study analog of vegetation response on sediment that might be exposed from removal of a tall dam. Early vegetation recovery on the exposed reservoir bottom was a combination of (1) vegetation colonization on bare, moist substrates typical of riparian zones and reservoir sediment of shallow dams and (2) a shAuthorsG.T. Auble, P.B. Shafroth, M.L. Scott, J. E. RoelleDefining ecosystem flow requirements for the Bill Williams River, Arizona
Alteration of natural river flows resulting from the construction and operation of dams can result in substantial changes to downstream aquatic and bottomland ecosystems and undermine the long-term health of native species and communities (for general review, cf. Ward and Stanford, 1995; Baron and others, 2002; Nilsson and Svedmark, 2002). Increasingly, land and water managers are seeking ways toTamarisk control, water salvage, and wildlife habitat restoration along rivers in the western United States
In the latter part of the 19th century, species of the nonnative shrub tamarisk (also called saltcedar; for example, Tamarix ramosissima, T. chinensis) were introduced to the United States for use as ornamental plants for erosion control. By 1877, some naturalized populations had become established, and by the 1960s, tamarisk was present along most rivers in the semi-arid and arid parts of the WesAuthorsPatrick B. ShafrothTamarisk research priorities of land and water managers: results from a USGS partnership meeting
No abstract available.AuthorsL. Hanson, P.B. Shafroth, F. D'ErchiaControl of Tamarix in the western United States: Implications for water salvage, wildlife use, and riparian restoration
Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (sAuthorsP.B. Shafroth, J.R. Cleverly, T.L. Dudley, J.P. Taylor, Charles van Riper, E.P. Weeks, J.N. StuartDating floodplain sediments using tree-ring response to burial
Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observAuthorsJ. M. Friedman, K.R. Vincent, P.B. ShafrothDominance of non-native riparian trees in western USA
Concern about spread of non-native riparian trees in the western USA has led to Congressional proposals to accelerate control efforts. Debate over these proposals is frustrated by limited knowledge of non-native species distribution and abundance. We measured abundance of 44 riparian woody plants at 475 randomly selected stream gaging stations in 17 western states. Our sample indicates that TamariAuthorsJ. M. Friedman, G.T. Auble, P.B. Shafroth, M.L. Scott, M.F. Merigliano, M.D. Freehling, E.R. GriffinHybridization of Tamarix ramosissima and T. chinensis (saltcedars) with T. aphylla (athel) (tamaricaceae) in the southwestern USA dertermined from DNA sequence data
Morphological intermediates between Tamarix ramosissima or T. chinensis (saltcedars) and T. aphylla (athel) were found recently in three locations in the southwestern USA, and were assumed to be hybrids or a previously unreported species. We sequenced chloroplast and nuclear DNA from putative parental and hybrid morphotypes and hybrid status of morphological intermediates was supported. ChloroplasAuthorsJohn F. Gaskin, Patrick B. ShafrothTamarisk tensions
In the August 2005 feature article, “Tiff over Tamarisk: Can a Nuisance Be Nice, Too?” the author raises several issues about which there is currently scientific debate, and presents some of the differing perspectives. A phenomenon surrounding discussions of tamarisk in the West is revealed and reinforced in the article—the polarized nature of the debate. Over the years, this polarization has fuelAuthorsPatrick B. ShafrothVegetation responses to dam removal
No abstract available.AuthorsPatrick B. Shafroth, Jonathan M. Friedman, Gregor T. Auble, Michael L. ScottNon-USGS Publications**
Shafroth, P.B., J.C. Stromberg, D.T. Patten, A.E. Springer, and J.M. Wright. 1996. Ground-water recharge and riparian habitat enhancement from water discharged from New Waddell Dam into the Agua Fria River: Phase I--Planning and feasibility. Final Report to Arizona Dept. of Water Resources - Phoenix Active Management Area. Phoenix, AZ78+ap p.Shafroth, P.B., J.M. Friedman, and L.S. Ischinger. 1994. River salinity has little influence on establishment of cottonwood and saltcedar. Research Information Bulletin 94-95. NBS Information Bulletin.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.