Lacrecia Johnson, Ph.D. 2011, Texas Tech University
Dr. David Haukos
Texas Tech University
U.S. Fish and Wildlife Service
Dr. Loren Smith
Dr. Scott McMurry
Location: Texas, New Mexico, and Oklahoma
(1) Evaluate physical loss and modifications of playas as a function of anthropogenic impacts.
(2) Develop the framework of a functional assessment for Great Plains playa wetlands
(3) Estimate the effect of the USDA soil eclassification and subsequent emapping of upland and depressional soils in the SHP of Texas.
(4) Quantify the effectiveness and impact of vegetative buffers of different widths and vegetation structure around playa wetlands on concentrations of metals, nutrients, and sediment in precipitation runoff and total volume of water entering playas.
Progress and Results:
Playas form the primary wetland system in the High Plains portion of the
Southern Great Plains (SGP) and provide valuable ecosystem services and functions
including being key sites for biodiversity. Current estimates of the number of playas
within the SGP (Texas, New Mexico, Oklahoma, southwestern Kansas, southeastern
Colorado) from historical soil surveys (pre-1970s), topographic maps, and field
checks exceed 25,000. This number often gives the potentially mistaken impression
that there are numerous, adequately functioning playas in the region that continue
to meet ecological and societal needs. In addition, these historical estimates are
used to generate samples of playas for a variety of natural resource survey and
research efforts, which depend on the occurrence of functional playas to generate
sound inferential results. During the time period of 1970-2008 an estimated 17% of
playas have been physically lost from the SGP landscape. Through the application of
the function matrix, none of the sampled playas were estimated to function at full
functional capacity in the SGP. Seventy-three (47%) of playas were estimated to be
partially functional and restorable. Partially functional and non-restorable due to
cost playas were estimated at 12.9% or 20 playas, and 61 (39.4%) playas were
partially functional and non-restorable because effective restoration techniques do
not exist. The effect of buffers surrounding playa wetlands on water quality was
evaluated as functions of buffer width and vegetation cover. TDS and TSS reached a
combined maximum removal at 50 m, 49% and 72% respectively. Nitrate and phosphorus
reached a combined maximum removal at a distance of 20 m, 49% and 33% respectively.
Maximum removal of metals occurred at 40 m. Estimated percent reduction in runoff
reaching the playas due to the presence of a buffer was greatest for the native CRP
cover type (-5.8%). A minimum buffer width of 40-50 m is necessary to maximize
contaminant removal from runoff entering playa wetlands.
Products since 2010:
Johnson, L. 2011. Current status and function of playa wetlands on the Southern Great Plains. Dissertation, Texas Tech University.
Johnson, L.A., D.A. Haukos, L.M. Smith, and S.T. McMurry. 2011. Jurisdictional loss of playa wetlands caused by reclassification of hydric soils on the Southern High Plains. Wetlands 31:483-492.
Johnson, L.A., D.A. Haukos, L.M. Smith, and S.T. McMurry. 2012. Loss and modification of Southern Great Plains playas. Journal of Environmental Management In Press.
Johnson, L., D.A. Haukos, L.M. Smith, and S. McMurry. 2011. Current status and function of Southern Great Plains playas wetlands and evaluation of buffer effectiveness: Implications for future conservation efforts. Final Report U.S. Environmental Protection Agency Cooperative Agreement CD-966441-01-0, Playa Lakes Joint Venture Project #445, U.S. Fish and Wildlife Service/U.S. Geological Survey Cooperative Agreement # 1434-HQ-07-RM-0068; TCRWFU RWO 67.
Johnson, L., D. Haukos, L. Smith, and S. McMurry. 2010. Effectiveness of wetland buffers as a conservation tool for playas. 46th Annual Meeting of the Texas Chapter of The Wildlife Society, Galveston, Texas.