Comm #7382
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Andropogon hallii Herbaceous Alliance
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accession code: VB.CC.19593.ANDROPOGONHALLI
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Western Ecology Working Group of... |
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This alliance includes herbaceous vegetation with Andropogon hallii, occurring in the Great Plains from the United States-Canada border south to Texas. It is dominated by tall and midgrass species, with shortgrass species becoming important in the western portion of its range. Andropogon hallii is usually dominant or codominant. Calamovilfa longifolia is present to codominant in most stands south of the South Dakota-Nebraska border. Hesperostipa comata (= Stipa comata), Koeleria macrantha, Schizachyrium scoparium, Bouteloua gracilis, Bouteloua hirsuta, Eragrostis trichodes, Pascopyrum smithii, and Sporobolus cryptandrus are typical grasses in stands of this alliance. Upland sedges are also very common, especially Carex filifolia, Carex inops ssp. heliophila, and Carex duriuscula (= Carex eleocharis). Although graminoids are overwhelmingly dominant, several species of forbs can be found in many stands of this alliance. Some of the more common forbs are Ambrosia psilostachya, Psoralidium spp., Ipomoea leptophylla, Liatris punctata, and Tradescantia occidentalis. There may be widely scattered low shrubs, including Rosa woodsii, Prunus pumila var. besseyi, and Yucca glauca. In west Texas common associates on deep sands include Panicum havardii, Sporobolus giganteus, and Calamovilfa gigantea. Stands of this alliance occur on sand deposits, usually on gentle to steep slopes but sometimes on flat ground. The soils are sand, loamy sand, or sandy loam. They can be poorly to moderately well-developed. There is little runoff or evaporation because moisture quickly sinks into the coarse soil. Soil near the surface is consequently dry throughout much of the year, but moisture is present further down, favoring deep-rooting species such as Andropogon hallii and Calamovilfa longifolia. Wind sometimes scours sand and vegetation from small areas, creating blowouts. These bare spots are initially colonized by species that are uncommon in this alliance, such as Muhlenbergia pungens and Redfieldia flexuosa. Eventually, these blowouts succeed to one of the communities in the V.A.5.N.a Andropogon hallii Herbaceous Alliance (A.1193). These grasslands occur on semi-stabilized quartz sand dunes in eastern Trans-Pecos Texas, where they form landscape mosaics with Quercus havardii shrublands, wetland dune swales, and sparsely vegetated dunes. The rare plant, Penstemon haydenii, an endemic to dune blowouts in the sandhills of Nebraska, may be endangered by the decline in habitat because of fire suppression and low to moderate stocking rates (Harrison 1980). |
Comm #7389
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Brasenia schreberi Herbaceous Vegetation
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accession code: VB.CC.23518.BRASENIASCHREBE
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Southeastern Ecology Working Gro... |
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This vegetation occurs in a range of natural ponds and impoundments, including ponds, beaver ponds, and lake margins. Brasenia schreberi is the dominant plant species; other species may include Leersia oryzoides, Lemna valdiviana, Juncus effusus, Stuckenia pectinata (= Potamogeton pectinatus), Nymphaea odorata, and Spirodela polyrrhiza. An occurrence along the Texas coast at McFaddin National Wildlife Refuge occupies the `open water' areas interspersed with emergent vegetation and `flotant' marsh dominated by Panicum hemitomon, Panicum hemitomon Semipermanently Flooded Herbaceous Vegetation (CEGL004665). Other floating aquatics present include Nelumbo lutea, Nymphaea odorata, Nymphaea mexicana, and Utricularia spp. along with submersed aquatics such as Cabomba caroliniana and Ceratophyllum demersum and rooted aquatics such as Pontederia cordata, Zizaniopsis miliacea. Additional information is needed on the full range and variability of expression of this vegetation. |
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