Texas Prairie Dawn is on the Comeback Around Houston by Jason Singhurst

 

The road to full recovery for Texas prairie dawn since its rediscovery in 1981 is still far out on the horizon, but land acquisitions, restoration, management, and partnerships are making great progress for this unique yellow wildflower.

Prairie dawn (Hymenoxys texana) is restricted to the Gulf Coastal Prairies in the upper coast of Texas with its core range centered on Houston (Fort Bend and Harris Counties) with two disjunct isolated prairie populations, one in Greg County and one in Trinity County. The species was first collected in 1889 near Hockley, Texas, in Harris County by F. W. Thurow. Hockley is renowned by many geologists for its famed Hockley Salt Dome, a mound or columns of salt that rise above parent geology to the surface. Until 1970, the prairie dawn species appeared to have vanished from Texas botany. It is not listed in Texas Plants - A Checklist and Ecological Summary by Dr. Frank Gould (1962). Correll and Johnston (1970), in the Manual of the Vascular Flora of Texas, state "Rare in sandy soils near Hockley and Houston, Harris County, probably extinct (no known collections after 1900)." In 1981, James W. Kessler discovered three populations growing in "buffalo wallows" -- or small depressions -- in Harris County, these being the first known collections of this species since 1889-90 (Mahler 1983).

Prairie dawn is limited to 'saline prairies' with cryptogamic soils within the Houston Coastal Prairie dominated by gulf coast muhly (Muhlenbergia capillaris). Many of the species that occur in these rare saline prairies are absent from or uncommon in adjoining vegetation. These soils are shallow, saline, and support a moderate diversity of annual and perennial herbs that commonly occur in barren slicks and at the base of mima mounds (Bierner 2005). It is thought that the natural pattern of disturbance (droughts, fires, and floods) is necessary to maintain the areas, though the exact role disturbance may play is not clear.

Prairie dawn was listed as endangered by U.S. Fish and Wildlife Service (1986). The founding information was assembled by Bridges (1988). Approximately 60 occurrences (TxNDD 2013) of prairie dawn have been recorded, these primarily in Harris County. Unfortunately, many of these occurrences have been lost to development. Today, there are only 11 occurrences; nevertheless huge conservation strides have moved the bar forward towards recovery of this species in the greater Houston area.

After the 1981 rediscovery, prairie dawn was documented at Addicks and Barker Reservoirs in 1986, lands owned by the United States Army Corp of Engineers (USACE). Addicks and Barker Reservoirs are located near the intersection of Interstate 10 and State Highway 6, in the upper watershed of Buffalo Bayou. The 26,000 acres that makes up Addicks and Barker Reservoirs are publically accessible and provide flood damage reduction along Buffalo Bayou downstream of the reservoirs and through the center of the City of Houston. This amazing tract of land also contains large populations of prairie dawn. Since the 1986 discovery, extensive botanical surveys have been conducted, which has resulted in many populations of prairie dawn found throughout this landscape. USACE has conducted annual monitoring surveys and population estimates. USACE has also utilized Geographic Information Science (GIS) and Global Position System (GPS) tools to map populations and provide this data to Texas Parks and Wildlife Department's Texas Natural Diversity Database. USACE has also mapped invasive plants that occur adjacent to or within the saline prairies that prairie dawn inhabits. USACE is utilizing this digital data within their natural resource plan with application to reduce invasive plants such as Chinese tallow, Macartney rose, and deep-rooted sedge that threaten prairie dawn populations.

Katy Prairie Conservancy (KPC), is a local land trust organized for the preservation of the remaining Katy Prairie remnants in northwest Harris County, near the city of Katy. KPC owns and manages a total of 18,000 acres of conservation land which includes two extremely significant prairies, Warren Prairie (285 acres) and Jack Road Prairie (511 acres) that were purchased as conservation areas to preserve two large prairie dawn populations. Warren and Jack Road Prairies lie adjacent to the Hockley Salt Dome. These prairie dawn populations have been surveyed almost annually since 2003, and in 2008-2009 a census was conducted by Wesley Newman, KPC Conservation Stewardship Director, Nancy Shackelford (University of Western Australia) and Jason Singhurst (Botanist, TPWD) to estimate the population size.

A population of prairie dawn documented back in 1988 was purchased through mitigation funds and is now owned by Harris County Parks and called Prairie Dawn Preserve. This preserve is being managed by Anita Tiller, a botanist with Mercer Arboretum, in north Harris County.

Harris County Parks also owns a tract of land in southeast Harris County called the Native Coastal Prairie Preserve adjacent to Ellington Field Airport. This prairie landscape is also referred to as Armand Pothole and sits on a salt dome. This preserve, also purchased through mitigation funds, had been neglected for several years which has allowed invasive woody plant growth (primarily Chinese tallow). However, recent discussion with Harris County Parks and Coastal Prairie Partnership to conduct ecologically sound management of invasive plants within the preserve looks promising.

Harris County Flood Control owns Willow Water Hole Prairie in south Harris County and is restoring this natural pocket prairie and planning interpretive signage. Not yet open to the public, plans for public visitation are in the works.

These are some of the gold star highlights with respect to migration towards recovery of prairie dawn throughout its restricted global range. Prairie dawn is also accompanied in the highly restricted saline prairie habitat with several other globally rare endemic plants, including coastal gayfeather (Liatris bracteata), Houston daisy (Rayjacksonia aurea), Texas windmill grass (Chloris texana), and three-flowered broomweed (Thurovia triflora). Therefore, each conservation success for prairie dawn benefits one or more additional globally rare plants. 

Jason Singhurst Is a botanist with Texas Parks and Wildlife Department working out of the Austin Headquarters.

References:

Bierner, M.W. 2005. Hymenoxys. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico 12+ vols. Oxford Univ. Press, New York and Oxford. Vol.21.

Bridges, E.L. 1988. Endangered species information system species workbook for Hymenoxys texana, part II. U.S. Fish and Wildlife Service, Washington, D.C. 43 pp.

Correll, D.S. and M.C. Johnston. 1970. Manual of the Vascular Plants of Texas. Texas Research Foundation, Renner. Gould, F. W. 1962. Texas Plants - a checklist and ecological summary. MP-585. Tex. Agri. Exp. Sta., College Station.

Gould, F. W. 1962. Texas Plants - a checklist and ecological summary. MP-585. Tex. Agri. Exp. Sta., College Station.

Mahler, W.F. 1983. Rediscovery of Hymenoxys texana and notes on two other Texas endemics. Sida 10:87-91.

Texas Natural Diversity Database (TxNDD), 2013. Wildlife Diversity Program, Texas Parks and Wildlife Department, Austin, Texas.

U.S. Fish and Wildlife Service. 1986. Determination of endangered status for Hymenoxys texana. Fed. Reg. 51(49):8631-8633.

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