Wildlife Habitat Appraisal for the Proposed Allens Creek Reservoir Site
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B. WHAP Scores
Tables 2 through 7 are the WHAP scores for each WHAP site for each biological habitat component as described in Section IA of the WHAP document. Table 2 shows the scores for the forest and the grass habitat types along Allens Creek between FM 1458 and the Brazos River. This area consisted of a riparian forest bordered with grasses and herbaceous plants. The forest on the north side of the creek was wider, had a larger diversity and abundance of trees, and consequently scored higher than the south side forest on Component 2 Criteria A. Both forests are characterized as pecan/elm/hackberry forests and together scored an average of 0.82 out of a possible maximum of 0.95.
The dominant trees of the north side forest were pecan (Carya illinoiensis), cedar elm (Ulmus crassifolia) hackberry (Celtis laevigata), bumelia (Bumelia Lanuginosa), soapberry (Sapindus saponia var. drummondii), cottonwood (Populus deltoides), green ash (Fraxinus pennsylvanica), locust (Gleditsia triacanthos), huisache (Acacia smallii), and hawthorne (Crataegus spp.). The south side forest was less diverse. The dominant trees were pecan (Carya illinoiensis), Hercules club (Zanthoxylum clava-herculis),osage orange (Macura pomifera), possum haw (Ilex decidua), and bumelia (Bumelia lanuginosa ).The grass cover types are a mixture of different grasses and herbaceous plants characterized as mixed grass. The north side grassy area was partially wooded, while the south side had fewer woody species and was heavily grazed, accounting for the lower scores. The dominant herbaceous species on the north side were Carex cherokeensis, bermuda grass (Cynodon dactylon), bayou violet (Viola langloisii), and frostweed (Verbesina virginica). The dominant south side herbaceous species were croton (Crotonspp.), bullnettle (Cnidoscolus texanus), and lemon beebalm (Monarda citriodora). The average score was 0.53 out of a possible maximum of 0.87.
Table 3 displays the scores for the seven crop WHAP sites. Crops include cultivated cover or row crops for food or fiber production (Frye 1995) and were corn, sorghum, and cotton. No soybeans had been planted. These sites scored very consistently with the exception of Component 4 Criteria A and B, which relate to woody species. The woody species were in the tree-lined borders between and surrounding crop fields, and include hackberry (Celtis laevigata), hawthorne (Crataegus spp.), and willow (Salix nigra).The average WHAP score for all crop sites was 0.30 out of a possible maximum of 0.65. Common weedy plants occurring in cultivated fields consist of peppervine (Ampelopsis arborea), curly dock (Rumex crispus), ragweed (Ambrosia trifida), sharp pod morningglory (Ipomoea trichocarpa), johnson-grass (Sorghum halpense), Carex cherokeensis, nutgrass (Cyperus rotondus), lemon beebalm (Monarda citriodora), bitter paspalum (Paspalum amarum) and broom-wood (Melochia pyramidata).
Table 4 shows the scores for the pecan/elm/hackberry bottomland forest cover type. Forests are defined as groups of deciduous or evergreen trees that are mostly higher than 30 feet tall with 71 to 100 % canopy cover (closed crowns or nearly so) and containing an obvious midstory (Frye 1995). Bottomland forest cover type is primarily riparian forest or non-riparian bottomland hardwood areas. There is also a small portion which is young timber in areas that were relatively recently cultivated, such as Site 8. This accounts for the lower than typical score of 0.58. The two highest scores of 0.81 and 0.83 were for the area known as Alligator Hole. The maximum possible score for a forest is 0.95. The bottomland forests at the Allens Creek site are found in the bowl-like depression left by past meandering of the Brazos River.
These floodplain forests are often inundated in winter and spring and are subjected to erosion and deposition of sediments. This flood regime has a major influence on the community structure of these forests. Numerous canals have been constructed to drain the bottomland at the Allens Creek site and much of the original forests have been cleared and converted to cropland and pastureland. The largest remaining tract of bottomland forest at this site is Alligator Hole, which contains approximately 600 acres. A channel cuts through the center of this large depression, indicating past attempts to drain this wetland. Cedar elm (Ulmus crassifolia) inhabits drier areas on the outer edges of Alligator Hole. The forest in the wetter interior is composed of hackberry (Celtis laevigata), green ash (Fraxinus pennsylvanica), honey locust (Gleditsia triacanthos), black willow (Salix nigra) and water oak (Quercus nigra). Green ash is the dominant tree species in the wettest sites. The understory in Alligator Hole consists of hawthorne (Crataegus sp. ), yaupon (Ilex vomitoria), and swamp privet (Forestiera acuminata). Some areas of Alligator Hole are dense thickets of small shrubs and vines such as poison ivy (Toxicidendran radicans var. radicans), greenbrier (Smilax sp.), Virginia creeper vine (Parthenocissus quinquefolia) and trumpet creeper vine (Campsis radicans). These thickets are in early stages of succession and appear to be the result of past timber cutting.
The herb layer of the forest floor is sparse in many areas in Alligator Hole, and largely absent in the wetter sites. The layer is made up of aquatic species such as crowfoot sedge (Carex crus-corvi), lance-leaf waterwillow (Justicia ovata var . lanceolata), water pimpernel (Samulus ebracteatus), and shore milkweed (Asclepias perennis). In drier locations, the herb layer is comprised of Carex cherokeensis, bayou violet (Viola langloisi), poison ivy (Toxicidendron radicans var . radicans), and Virginia creeper vine (Parthenocissus quinqufolia). In the less frequently flooded bottomland forests at the Allens Creek site, cedar elm is often the dominant tree. Other important trees in these forest are hackberry (Celtis laevagata), pecan (Carya illinoiensis), osage orange (Maclura pomifera), green ash (Fraxinus pennyslvanica), and box elder (Acer negundo). Green ash is usually the most prevalent tree in seasonally flooded depressions within these forests. Understory shrubs in these bottomlands include yaupon (Ilex vomitoria), hawthorne (Crataegus sp.), and possum haw (Ilex decidua). The herb layer of these forests is made up of Carex cherokeensis, black snakeroot (Sanicula canadesis), bayou violet (viola langlosi), prostrate lawn flower (Calyptocarpus vialis), turk's cap (Malvaviscus arboreus var. drummondii), basket-grass (Oplismenus hirtellus var. setarius), Texas pinkroot (Spigelia texana), and a variety of other herbaceous plants.
The Allens Creek riparian forest upstream of FM 1458 is included in the bottomland forest classification. It consists of soil with a high sand content which supports a diversity of trees found nowhere else at the proposed reservoir site. Trees in this area include cedar elm (Ulmus crassifolia), pecan (Carya illinoiensis), hackberry (Celtis laevegata), sycamore (Platanus occidentalis), black willow (Salix nigra), water oak (Quercus nigra), laurel oak (Quercus laurifolia), and osage orange (Maclura pomifieri). An unusual proportion of these trees were large and mature. One sycamore, near the dilapidated bridge, measures 144 inches in circumference. The herb layer of much of the forest along Allens Creek is also diverse.
Table 5 shows the WHAP scores for the meander bluff created by the Brazos River which is the boundary on the north, west and south side of the proposed reservoir. The bluff area had the highest WHAP scores of any habitat cover type. This resulted from a greater diversity of woody and herbaceous species, and being rated as very uncommon, unique or irreplaceable (Component 3). Each WHAP site scored either 0.83 or 0.84 out-of a maximum possible 0.95. It displays a composition of trees that is strikingly different from the forests found at other locations at the proposed Allens Creek reservoir. This bluff is forested with bur oak (Quercus macrocarpa), durand oak (Quercus sinuata var. sinuata), cedar elm (Ulmus crassifolia), American elm (Ulmus americana), pecan (Carya illinoiensis), and hackberry (Celtis laevigata ). Bur oak and durand oak, which occur in abundance on the bluff, are largely absent from other forested sites in the proposed reservoir. Although the bur oak (Quercus macrocarpa) is more commonly found in the Blackland Prairies, the Cross Timbers and Prairies, and the Post Oak Savannah in north and east-central Texas, it also occurs on riverbanks and valleys of the central part of the Gulf Prairies and Marshes area of Texas (Simpson 1988). Besides the bluff forest at the proposed Allens Creek reservoir, the bur oak is also reported from a number of sites along the Brazos valley including the bottomland forests at Brazos Bend State Park (Williams 1988). Another oak that occurs plentifully on the bluff is durand oak (Quercus sinuata var. sinuata). The durand oak, uncommon throughout its range, inhabits alluvial soils along streams from east Texas to the Edwards Plateau (Tull and Miller 1991). This oak is also found in palmetto flats in the Brazos riverbottom. in Brazoria County (Simpson 1988).
The understory shrub composition of the bluff forest is dominated by Mexican buckeye (Ungnadia speciosa), a southwestern species that is uncommon in this region of Texas. The Mexican buckeye population at the proposed Allens creek reservoir is near the eastern limits of its range. The red buckeye (Aesculus pavia var. pavia), not closely related to the Mexican buckeye, is also an important component of the understory in the bluff forest. The herbaceous laver of this forest includes green dragon (Arisaema dracontium), broadleaf woodoats (Chasmantheium latifolia), Carex cherokeensis, pigeon berry (Rivina humilis), heartleaf scullcap (Scutellaria ovata var. bracteata) and frostweed (Verbesina virginica). This unusual mixture of flora is best represented on the bluff in the vicinity of the microwave tower.
Most of the original forest on the south end of the bluff has been cleared and converted to pastureland. On the north end of the bluff, the forest is dominated by cedar elm (Ulmus crassifolia), with bur oak (Quercus macrocarpa) and durand oak (Quercus sinuata var. sinuata) largely absent. The north end of the bluff displays fewer components of the unusual flora found on the middle section of the bluff. Although much of the bluff has clay loam soil, deep sand deposits occur in scattered locations. These sandy areas contain a more open xeric community with scattered groves of wooly bumelia (Bumelia lanuginosa), red buckeye (Aesculus pavia var. pavia), cedar elm (Ulmus crassifolia) and Hercules club (Zanthoxylum clava-herculis). Open areas contain grasses and herbaceous vegetation with scattered yucca (Yucca arkansana) and prickly pear (Opuntia compressa).
Table 6 contains the WHAP scores for the mixed grass cover type ranging from 0.49 to 0.52. The maximum possible score was 0.87. With the exception of the crops cover type, the grass cover type scored the lowest. These mixed grasses are herb dominated sites that lack woody vegetation and 10% or less of a woody canopy cover (Frye 1995). All seven grass sites surveyed at the proposed Allens Creek reservoir are pastures used for cattle grazing. A number of these sites are overgrazed resulting in low grass abundance. These sites consist largely of weedy species such as giant ragweed (Ambrosia trifida), sumpweed (Iva annua), Eryngium hookeri, snow on the prairie (Euphorbia bicolor), frog fruit (Phyla incisa), balloon-vine (Cardiospermum halicacabum) and peppervine (Ampelopsis arborea). A total of 13 species of grasses were reported from all seven sites. Virginia wild rye (Elymus virginicus) was recorded from five of the seven sites. Bermuda-grass (Cynodon dactylon) was recorded from four of the seven sites. Other grasses noted from the seven grass sites include carpetgrass (Axonopus affinis), King Ranch bluestem (Bothrichloa ischaemum), rescuegrass (Bromus unioloids), Dicanthelium sp., southern crabgrass (Digitaria cilliaris), foxtail barley (Hordeum pusillum), bitter panicurn (Panicum amarum), common witchgrass (Panicum capillare), Dallisgrass (Paspalum dilatatum), bahiagrass (Paspalum notatum) and johnson-grass (Sorghum halpense). One sedge species, Carex cherokeensis, was found in all sites surveyed. Crowfoot sedge (Carex crus-corvi) was present in two survey sites.
Table 7 shows the WHAP scores for the only two park cover types in the proposed reservoir. Both had moderate scores averaging 0.66 out of a maximum possible 0.95. Parks are composed of trees that are equal to or greater than 9 feet tall and having a canopy cover varying from 11% to 70%. Trees in parks occur in small groups or as scattered individuals within a matrix of grasses and other herbaceous plants (Frye 1995). The two parks surveyed at the proposed Allens Creek reservoir resemble the bottomland forests. Dominant trees in these two parks include pecan (Carya illinoiensis), hackberry (Celtis laevigata), cedar elm (Ulmus crassifolia), honey locust (Gleditsia triacanthos) and green ash (Fraxinus pennsylvanica). A total of eight species of grasses were recorded from the two parks. Bermuda grass (Cynodon dactylon) and Virginia wild rye (Elymus virginicus) were the only grasses noted from both park sites. Sedges recorded at these sites consist of Carex cherokeensis, nutgrass (Cyperus rotundus), and other Cyperus spp.
Beebalm (Monarda spp.), Croton spp., curly dock (Rumex crispa), and shore milkweed (Asclepias perennis) are common forbs occurring in these parks. Understory shrubs present were coral berry (Symphoricarpos orbiculata), hawthorn species (Crataegus spp.), yaupon (Ilex vomitoria), and possum haw (Ilex decidua). Prevalent vines in these sites include poison ivy (Toxicidendron radicans), passion flower (Passiflora incarnata), balloon-vine (Cardiospermum halicacabum), dewberry (Rubus sp.) and pepper-vine (Ampelopsis arborea).