Sandra Rideout-Hanzak

Biomass Not Linked to Perennial Grass Mortality Following Severe Wildfire in the Southern High Plains

Abstract In March 2006 the East Amarillo Complex (EAC) wildfires burned over 367 000 ha of short and mixed grass prairie of the southern High Plains, USA. We studied EAC wildfire effects on perennial grass mortality and peak standing crop on Deep Hardland and Mixedland Slopes ecological sites. Deep Hardlands were dominated by blue grama (Bouteloua gracilis H.B.K. [Griffiths]) and buffalograss (Buchloe dactyloides [Nutt.] Engelm.); common species on Mixedland Slopes were little bluestem (Schizachyrium scoparium [Michx.] Nash.) and sideoats grama (Bouteloua curtipendula [Michx.] Torr.) with scattered sand sagebrush (Artemisia filifolia Torr.) sometimes present. We hypothesized that perennial grass mortality would increase and standing crop would decrease following severe wildfire, and that these responses would be greater than documented prescribed fire effects. Frequency of perennial grass mortality was higher on both sites in burned areas than nonburned areas through three growing seasons following wildfire; however, standing crop was minimally affected. Results suggest that post-wildfire management to ameliorate wildfire effects is not necessary, and that wildfire effects in this area of the southern High Plains are similar to prescribed fire effects.

Grassland Bird Communtiy Response To Large Wildfires

Abstract We studied breeding season communities of grassland birds on short-grass and mixed-grass prairie sites during the second and third breeding seasons following two large wildfires in March 2006 in the Texas panhandle, USA. There was an apparent temporary shift in avian community composition following the fires due to species-specific shifts associated with life-history traits and vegetation preferences. Species that prefer sparse vegetation and bare ground on short-grass sites, such as Horned Lark (Eremophila alpestris), benefited from wildfires, while others, such as Western Meadowlark (Sturnella neglecta), that prefer more dense vegetation, were negatively impacted. Mixed-grass sites had species-specific shifts in 2007, two breeding seasons after the fires; grassland bird communities on burned plots were similar by 2008 to those on unburned plots. Avian communities appeared to return to pre-burn levels within 3 years following wildfires. Many of the responses in our study of wildfire were similar to those reported following prescribed fires elsewhere. Prescribed fires appear to have similar effects on the avian community despite differences in intensity and environmental conditions during wildfires.

Effects of Depth and Duration of Burial on Tanglehead ( Heteropogon contortus ) Seed Viability and Germination in Southern Texas

and is freely available online at: http://er.uwpress.org Effects of Depth and Duration of Burial on Tanglehead (Heteropogon contortus) Seed Viability and Germination in Southern Texas Joshua L. Grass (Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, Kingsville, TX, 78363), Aaron D. Tjelmeland (The Nature Conservancy, Texas City Prairie Preserve, Texas City, TX, 77590), Forrest S. Smith, (Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, Kingsville, TX, 78363), Scott L. Mitchell (Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, Kingsville, TX, 78363), Sandra Rideout-Hanzak (Caesar Kleberg Wildlife Research Institute and Dept. of Animal, Rangeland and Wildlife Sciences, Texas A&M University-Kingsville, Kingsville, TX, 78363-8202), John Lloyd-Reilley (E. “Kika” de la Garza Plant Materials Center, USDA NRCS, Kingsville, TX, 78363-2704), Shelly D. Maher (E. “Kika” de la Garza Plant Materials Center, USDA NRCS, Kingsville, TX, 783632704) and David B. Wester (corresponding author: Caesar Kleberg Wildlife Research Institute and Dept. of Animal, Rangeland and Wildlife Sciences, Texas A&M UniversityKingsville, Kingsville, TX 78363, david.wester@tamuk.edu).

Season and Intensity of Burning on Two Grass Species of the Chihuahuan Desert

Abstract We investigated effects of three burning seasons under two simulated fuel loads on plant mortality and basal area of small and large blue grama (Bouteloua gracilis [H.B.K.] Lag) and broomgrass muhly (Muhlenbergia rigida [H.B.K.] Lag) plants in the southern Chihuahuan Desert of Mexico. We simulated prescribed fire with a portable propane burner calibrated to match time and temperature curves reached at 1 700 kg · ha−1 and 2 800 kg · ha−1 fine fuel loads. Large (initial basal area > 10 cm2) and small (initial basal area ≤ 10 cm2) plants were used. For each species, we randomly treated 50 plants in each size class each season at each fuel load; 50 control plants of each species and size received no fire treatment. We estimated basal area change from measurements recorded photographically. Blue grama mortality was affected by season of burning, simulated fuel load, and plant size. Small blue grama plants had higher mortality than large plants. Burning at the high fuel load in winter increased basal area of large blue grama plants; in contrast, basal area was not affected by summer burning, and was reduced by spring burning with high fuel load. Basal area of broomgrass muhly plants was reduced by summer and winter burning and these responses were independent of fuel load and plant size. Our results suggest that winter is the most suitable season for prescription burning to improve southern Chihuahuan Desert grasslands: prescribed fire during this time reduced basal area of broomgrass muhly plants, had the highest mortality on broomgrass muhly, had a positive effect on basal area of small blue grama plants, and had no effect on basal area of large blue grama plants.

A Nondestructive Method to Estimate Standing Crop of Purple Threeawn and Blue Grama

Abstract We used multiple regression analysis to develop models to predict standing crop of purple threeawn (Aristida purpurea Nutt.) and blue grama (Bouteloua gracilis [H.B.K.] Griffiths) nondestructively. Data were collected for 3 yr on the Texas Tech University Native Rangeland, Lubbock, TX, USA. Independent variables included plant length and area measurements (basal area and cross-sectional area at a 7.5-cm plant height and at 50% of total plant height). One hundred randomly selected plants of each species were measured in June 2008; 50 plants of each species were measured in June 2009 and 2010. Coefficients of determination exceeded 0.91 for both species in all 3 yr of measurement. For both species and years, cross-sectional area at 7.5 cm was the most important single predictor variable. For each species, models differed among years. Our regression models were successful at predicting mid- to late-season standing crop of purple threeawn and blue grama grass and provide an effective method for nondestructive monitoring of these species. This approach should be applicable to similar morphotypes of these species. Resumen Usamos un análisis de regresión múltiple para desarrollar modelos no destructivos para predecir la producción de purple threeawn (Aristida purpurea Nutt.) y blue grama (Bouteloua gracilis [H.B.K.] Griffiths). Los datos fueron recolectados durante 3 años en el pastizal nativo de Texas Tech University, Lubbock TX, USA. Variables independientes incluyeron longitud de la planta, y mediciones de área (área basal y área de la sección transversal a 7.5 cm de la altura de la planta, área de la sección transversal al 50% del total de la longitud de la planta). Cien plantas de cada especie fueron seleccionadas aleatoriamente y medidas en junio de 2008; 50 plantas de cada especie fueron medidas en junio de 2009 y 2010. Los coeficientes de determinación excedieron 0.91 para ambas especies durante los tres años que se llevaron a cabo las mediciones. Para ambas especies y años, el área transversal a la altura de 7.5 cm fue la variable única de predicción más importante. Para cada especie, los modelos fueron diferentes entre años. Nuestros modelos de regresión fueron exitosos en la predicción de la biomasa en la etapa media a tardía de crecimiento de de los pastos purple threeawn y blue grama y proporcionan un método efectivo no destructivo para el monitoreo de estas especies. Esta metodología debería ser aplicable para morfo tipos similares de estas especies.

Effects of burns conducted in summer and winter on vegetation of Matagorda Island, Texas.

Abstract We conducted prescribed fires on Matagorda Island, Calhoun County, Texas, in late summers (August) and early winters (January) of 1992–1993 and 1993–1994 to determine responses of vegetation and litter. There were reduced litter loads 1 year after burning, but they approached pre-burn levels 2 years after burning. There was no difference in production of grasses, forbs, or the Juncus and other-Cyperaceae complex 1 year after burning. There was a significant difference in production of Juncus and other Cyperaceae when years were compared. We presume this was caused by differences in precipitation between years. There was no difference in percentage frequency between burned and control plots 1 year after burning for most species examined. However, burning in summer significantly increased occurrences of coastal mistflower (Conoclinium betonicifolium), Fabaceae, and Cyperaceae (other than Juncus) over control plots 1 year after treatment. Beach groundcherry (Physalis cinerascens) and Fabaceae also were increased by burning in summer 2 years following treatment. Prescribed burning did not affect density of vertical structure. Because coastal barrier islands serve as important wintering grounds and stopovers for many migratory birds, we recommend conducting burns in late summer every 2–5 years to increase incidence of legumes and other forage for wildlife.

Tanglehead in Southern Texas: A Native Grass with an Invasive Behavior

On the Ground Tanglehead is a native bunchgrass with a pan-tropical distribution. Historically, tanglehead was common but not abundant in southern Texas and was considered a decreaser whose presence indicated good range condition. Beginning in the late 1990s, the Texas Coastal Sand Plain ecoregion witnessed dramatic increases in the abundance and distribution of tanglehead: thousands of acres of former grasslands were replaced by dense monotypic stands of tanglehead, reducing habitat quality for livestock and wildlife. Our research has focused on understanding factors related to tangleheads expansion, its effects on habitat quality, and management practices that can improve range condition and habitat quality.

Soil Seed Banks in Stock-piled Topsoils in the Western Rio Grande Plains, Texas

Topsoils often are removed from energy production sites and stock-piled for use later in restoration activities. Effects of this practice on soil seed banks are unknown. We examined seed bank size, species richness, and species composition of stock-piled topsoils as affected by sampling depth and sampling date at two study sites in the western Rio Grande Plains, TX, USA. Stock-piled topsoil and adjacent non-disturbed topsoil samples were collected at 0–10, 10–20, 20–30 and 30–40 cm depths on five dates over an 18-month period following stock-pile construction. Seed banks were assessed with the seedling emergence method. Sampling date had little effect on seed bank characteristics. We detected differences among depths on the stock-pile, and between stock-piles and undisturbed soil. Seed bank size and species richness generally decreased with increased stock-pile sampling depth at both sites. Differences between stock-piles and undisturbed soil varied between sites: at one site, stock-piling effects were common and were expressed in lower seed bank size and richness in stock-piles compared to undisturbed soils; at the other site, stock-piling had fewer effects on richness or seed bank size. Prevalence of exotic species varied between sites and likely reflected differences in surrounding vegetation. Therefore, site-to-site variability precludes strong generalizations. However, density of emerged native seedlings ranged from < 1 to 3.8 seedlings m−2 at both sites. Assuming acceptable species composition, stock-piles supported an adequate seed bank size at time of sampling for restoration without need for additional seed input.

Evaluating Removal of Competition on Morphology of Endangered Slender Rush-Pea (Hoffmannseggia tenella) Endemic to Southern Texas, USA

ABSTRACT: Slender rush-pea (Hoffmannseggia tenella) is an endangered herbaceous legume endemic to southern Texas. Agricultural expansion and invasive nonnative grasses have caused reductions in its range, threatening existing populations. We compared three management techniques that control competition to no management (control) to determine effects on slender rush-pea survival and morphology. We treated some slender rush-pea plants with summer prescribed burning. In the mechanical treatment we controlled above-ground competition surrounding target slender rush-pea plants with a string trimmer and we removed both above- and below-ground competition with herbicide in the chemical treatment. No slender rush-pea plants died during our two-year study. Plants in each competition removal treatment produced more main stems than control plants at various times throughout the study. Summer prescribed burning produced longer stems, while both summer burning and chemical treatment resulted in more leaves on the longest stem and more flowers than control plants at various times throughout the study. Slender rush-pea individuals with more main stems, longer stems, and more leaves may be more robust and resilient to environmental stress. We speculate increased flower production may indicate enhanced reproduction. At the pasture scale herbicide treatment is not practical as it may eradicate remaining native plants. Summer prescribed burning may be the most effective method for increasing short-term robustness of slender rush-pea; mowing could be a temporary substitute when fire is impractical. Results indicate that slender rush-pea benefits from active management and control of competition from nonnative grasses, and if managed properly slender rush-pea could persist in their presence.

Echinocereus viridiflorus Var Viridiflorus Mortality in Shortgrass Plains of Texas: Observations Following Wildfire and Drought

Abstract: A wildfire of unknown origin ignited in October 2005 at Buffalo Lake National Wildlife Refuge in Randall County, Texas, burning approximately 300 ha of shortgrass plains typified by blue grama (Bouteloua gracilis) and buffalograss (Buchloe dactyloides). Above-average rainfall in the year preceding the fire resulted in abundant herbaceous vegetation and, therefore, fine fuel production. Precipitation following the fire was below normal. We compared density, condition (dead or alive), basal diameters, and heights of Echinocereus viridiflorus var viridiflorus (nylon hedgehog cactus) in a population that was burned by the wildfire and a population in a nearby non-burned area. By May 2006, total density of cacti was similar in the burned and non-burned areas. However, percent mortality was significantly higher, and living plants were both shorter and narrower, in the burned population. Although mortality was high (91%), the wildfire did not kill all of the burned population. It is possible that more cacti would have survived with normal rainfall in the months following the wildfire.