Lance T. Vermeire

Agricultural Research Service, Kerrville, Texas, United States

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Publications (39)50.12 Total impact

  • Rangelands 04/2015; DOI:10.1016/j.rala.2015.03.003
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    ABSTRACT: Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? We evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along mean annual temperature (MAT; ~7-14 °C) and mean annual precipitation (MAP; ~250-500 mm) gradients. We used regression and analysis of covariance to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. We also related ANPP to the standardized precipitation evaporation index (SPEI), which combines precipitation and evapotranspiration to better represent moisture available for plant growth. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a stronger predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI were as strongly related to ANPP as precipitation. We conclude that forecasted warming likely will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because, unlike precipitation, warming effects can be positive or negative and moderated by shifts in the C3/C4 ratios of plant communities.
    Oecologia 02/2015; 177(4). DOI:10.1007/s00442-015-3232-7 · 3.25 Impact Factor
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    ABSTRACT: In perennial grassland dominated systems, belowground bud banks regulate plant community dynamics. Plant community responses to disturbance are largely driven by the ability to generate future aboveground growth originating from belowground axillary buds. This study examined bud bank dynamics for Bouteloua gracilis, Hesperostipa comata, and Pascopyrum smithii following fire in northwestern mixed-grass prairie in eastern Montana, USA. Belowground axillary buds were counted and classified for three growing seasons to determine immediate and short-term effects of summer, fall, and spring prescribed burns on patterns of bud bank activity, dormancy, and mortality. Prescribed burns did not result in immediate mortality of B. gracilis, H. comata, or P. smithii buds. Surprisingly, spring prescribed burns immediately increased the number of active B. gracilis buds. Summer fire, however, reduced B. gracilis active bud numbers. Fall burns immediately activated P. smithii buds, whereas fire did not influence any immediate bud dynamics for H. comata. Reduced bud numbers of H. comata may limit the ability to respond to fire. Season of fire directly manipulated bud activity, dormancy, and mortality for these species throughout the growing and dormant seasons following fire. Using season of fire to manipulate bud bank dynamics illustrates potential to improve post-fire management strategies based on known bud development trajectories and bud dynamics following fire.
    Plant Ecology 01/2015; DOI:10.1007/s11258-015-0471-y · 1.64 Impact Factor
  • M.L. Russell, L.T. Vermeire
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    ABSTRACT: Belowground accumulation of vegetative buds provides a reservoir of meristems that can be utilized following disturbance. Perennial grass bud banks are the primary source of nearly all tiller growth, yet understanding of fire and nitrogen effects on bud banks is limited. We tested effects of fire and nitrogen addition on bud banks of purple threeawn (Aristida purpurea Nutt.), a perennial C4 bunchgrass. Fire (no fire, summer fire, fall fire) and nitrogen addition (0, 46, 80 kg·ha- 1) treatments were assigned in a completely randomized, fully factorial design and axillary buds were evaluated on two similar sites in southeastern Montana 1 and 2 years after fire. Permanently marked plants were assessed for live tiller production, and randomly selected tillers were sampled to determine active and dormant buds per tiller. Fire and nitrogen had opposite effects on axillary buds. Summer and fall fire reduced active buds by 42% relative to nonburned plots. Adding nitrogen at 46 or 80 kg·ha- 1 increased active buds per tiller 60% compared with plots with no nitrogen addition. The number of dormant buds per tiller was similar across fire treatments and levels of nitrogen. Fire and nitrogen had interacting effects on total buds at the tiller level. Without nitrogen addition, fall and summer fire reduced total buds per tiller about 70%. Nitrogen had no effect on total buds per tiller for nonburned plants. However, total number of buds per tiller was greater with nitrogen addition following fall fire and increased with each increase in nitrogen following summer fire. Results indicate fire effectively controls purple threeawn through bud bank reduction and that nitrogen can stimulate bud production. Interacting effects of fire and nitrogen on buds reveal a potential source of inconsistency in nitrogen effects and a possible method of facilitating recovery of fire-sensitive bunchgrasses after fire.
    Rangeland Ecology & Management 12/2014; 68(1). DOI:10.1016/j.rama.2014.12.009 · 1.46 Impact Factor
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    Rangeland Ecology & Management 05/2014; 67(3):298-306. DOI:10.2111/REM-D-13-00057.1 · 1.46 Impact Factor
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    ABSTRACT: In the face of an increasingly variable climate, long-term cattle weight gain datasets are rare, yet invaluable, for determining site-specific influences of seasonal weather patterns on cattle production. Here, we present a long-term (1936–2005) yearling Hereford steer dataset collected at the Northern Great Plains Research Laboratory (NPGRL) near Mandan, ND, USA. Data were analyzed using weighted AICc model averaging to examine the effects of spring (April–June) and summer (July–September) temperature and precipitation, as well as prior growing season (prior April–September) and prior fall/winter (prior October–March) precipitation on cattle production (kg/ha) under light (37.4 ± 5.3 SD Animal Unit Days [AUD]/ha across all study years) and heavy (91.6 ± 22.2 SD AUD/ha) stocking rates. Because Kentucky bluegrass (Poa pratensis L.) invaded the grassland at NPGRL in the early 1980s, we modeled cattle production separately for pre- (1936–1983) and post-invasion (1986–2005) years to determine if the plant community shift influenced sensitivity to seasonal weather patterns. Cattle production under heavy stocking was more sensitive to seasonal weather variability than under light stocking during both pre- and post-invasion years. Interestingly, the magnitude and robustness of coefficients changed between the pre- and post-invasion years, with seasonal weather patterns explaining more cattle production variation during the post-invasion years. Though cattle sensitivity to seasonal weather patterns differed between light and heavy stocking for both pre- and post-invasion years, invasion status did change cattle response to weather. For example, cattle production in P. pratensis invaded pastures was more heavily influenced by cool, wet springs and wet prior grazing seasons than was production in un-invaded pastures. For cattle stocked heavily in native pastures, wet winters more strongly increased cattle production than in invaded pastures.
    Agriculture Ecosystems & Environment 01/2014; 183:110–117. DOI:10.1016/j.agee.2013.10.030 · 3.20 Impact Factor
  • Lance T. Vermeire, Jessica L. Crowder, David B. Wester
    Rangeland Ecology & Management 01/2014; 67(1):52-60. DOI:10.2111/REM-D-13-00007.1 · 1.46 Impact Factor
  • Dustin J. Strong, Lance T. Vermeire, Amy C. Ganguli
    Rangeland Ecology & Management 09/2013; 66(5):553-560. DOI:10.2111/REM-D-13-00030.1 · 1.46 Impact Factor
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    ABSTRACT: a b s t r a c t Quantifying the effects of seasonal temperature and precipitation on cow–calf production on rangelands is challenging, as few long-term (420 yrs) studies have been reported. However, an understanding of how seasonal weather inconsistency affects beef production is needed for beef producers to better manage their herds on native rangelands to minimize enterprise risk with respect to climatic variability. Cow–calf beef production data collected at the USDA-ARS High Plains Grasslands Research Station near Cheyenne, WY, USA from 1975 to 2012 were tested using model averaging for effects of spring (April–June) and summer (July–September) temperature and precipitation, as well as prior winter (October–March) and prior growing season (April–September) precipitation on beef production. Two breeds were used at different times during the study period (Herefords from 1975 to 2001 and a Red Angus  Charolais  Sa-lers cross from 2003 to 2012; there was no grazing in 2002) and examined separately to test for differential effects of seasonal weather by breed. Herefords were more sensitive to seasonal weather patterns than the crossbreds, with Hereford pair total beef production showing the largest effect sizes and Hereford cows showing the highest R 2 value (0.66) among models. Wet springs and wet winters particularly increased Hereford beef production in this northern mixed-grass prairie, whereas beef production from the crossbreds did not show any weather effect patterns. The model structure used maximizes utility of these data to be built into decision support tools to help ranchers optimize stocking rates and minimize enterprise risk in advance of the grazing season. Published by Elsevier B.V.
    Livestock Science 08/2013; 155(2-3):355-363. DOI:10.1016/j.livsci.2013.04.015 · 1.10 Impact Factor
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    ABSTRACT: Cattle weight gain responses to seasonal weather variability are difficult to predict for rangelands because few long-term (>20 yr) studies have been conducted. However, an increased understanding of temperature and precipitation influences on cattle weight gains is needed to optimize stocking rates and reduce enterprise risk associated with climatic variability. Yearling steer weight gain data collected at the USDA-ARS High Plains Grasslands Research Station at light, moderate, and heavy stocking rates for 30 years (1982-2011) were used to examine the effects of spring (April-June) and summer (July-September) temperature and precipitation, as well as prior-growing-season (prior April-September) and fall/winter (October-March) precipitation, on beef production (kg . ha(-1)). At heavier stocking rates, steer production was more sensitive to seasonal weather variations. A novel finding was that temperature (relatively cool springs and warm summers) played a large predictive role on beef production. At heavier stocking rates, beef production was highest during years with cool, wet springs and warm, wet summers, corresponding to optimum growth conditions for this mixed C-3-C-4 plant community. The novelty and utility of these findings may increase the efficacy of stocking rate decision support tools. The parsimonious model structure presented here includes three-month seasonal clusters that are forecasted and freely available from the US National Oceanic and Atmospheric Administration up to a year in advance. These seasonal weather forecasts can provide ranchers with an increased predictive capacity to adjust stocking rates (in advance of the grazing season) according to predicted seasonal weather conditions, thereby reducing enterprise risk.
    Rangeland Ecology & Management 07/2013; 66(4):438-444. DOI:10.2111/REM-D-12-00157.1 · 1.46 Impact Factor
  • Rangeland Ecology & Management 05/2013; 66(3):290-296. DOI:10.2111/REM-D-12-00143.1 · 1.46 Impact Factor
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    Dustin J Strong, Amy C Ganguli, Lance T Vermeire
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    ABSTRACT: Fire behavior associated with wild and prescribed fires is variable, but plays a vital role in how a plant responds to fire. Understanding the relationship between fire behavior and rangeland plant community response will help to improve the use of prescribed fire to achieve management objectives. Fire is an important ecological process in many rangeland ecosystems and can be used as a tool to maintain grassland plant communities and shift community composition. Purple threeawn (Aristida pur-purea Nutt.) is a grass native to North America that has poor forage quality and the ability to form near monocultures. Therefore, the identification of tools to reduce purple threeawn abundance is desirable. We assessed the effects of summer and fall prescribed fire on purple threeawn plant basal area, tiller production , and plant mortality one growing season post fire in the northern Great Plains. Thermocouples and portable data loggers were used to measure the resumen
  • David H. Branson, Lance T. Vermeire
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    ABSTRACT: Rangeland fire is a common naturally occurring event and management tool, with the amount and structure of biomass controlling transfer of heat belowground. Temperatures that grasshopper eggs are exposed to during rangeland fires are mediated by species-specific oviposition traits. This experiment examined egg mortality in two slant-faced grasshopper species with differing oviposition traits, namely Aulocara elliotti (Thomas) and Opeia obscura (Thomas). We hypothesized that A. elliotti egg mortality would increase with fire intensity because the shallow egg location below the soil surface would result in exposure to higher temperatures, and that the deeper O. obscura eggs would not be affected by fire intensity. Fire intensity did not significantly affect the mortality of O. obscura eggs, with very low mortality in all treatments. Fire intensity significantly affected mortality of A. elliotti eggs, which are laid in shallow egg pods with the midpoint of the egg clutch at a depth of ∼ 0.825 cm. Aulocara elliotti egg mortality increased with higher levels of heat application, with 79% egg mortality in the 4 500 kg · ha -1 heat treatment. Heat effects on A. elliotti egg mortality were similar to those previously observed for another shallow-egg-laying species. Limited research has examined if rangeland fires reduce population densities of specific economically important grasshopper species. The results from this experiment indicate that grasshopper species with the midpoint of the egg pod less than 1 cm below the surface are likely in general to be vulnerable to fire-induced egg mortality during rangeland fires.
    Rangeland Ecology & Management 01/2013; 66(1):110-113. DOI:10.2307/23355275 · 1.46 Impact Factor
  • David H. Branson, Lance T. Vermeire
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    ABSTRACT: Background/Question/Methods Rangeland management practices such as burning or livestock grazing have the potential to manipulate the habitat of grasshoppers and/or their predators and thus impact population densities and community composition. Few studies have examined the effects of fire and grazing on grasshopper population dynamics in the northern Great Plains, especially during population increases. Interest in fire stems from its use as a management tool and unplanned events; however, there is increased interest in using fire to shift grazing animal distribution and to increase the structural heterogeneity of rangelands. As part of a study examining patch burning effects on plant community dynamics and grazing distribution in northern mixed prairie in Montana, we examined how patch burning and livestock grazing affects grasshopper population dynamics. Homogenous and heterogeneous management treatments were assigned to six pastures, with heterogeneity created by burning 25% of each treatment pasture in a given year. Patch burns occured during spring and fall of 2009. Total grasshopper density was estimated by counting the number of grasshoppers within a series of 60, 0.1m2 aluminum wire rings in each plot, with sweep net samples used to establish grasshopper community composition. Results/Conclusions Patch burning effects on grasshopper populations differed significantly between the spring and fall patch burn, likely due to differences in the timing of fire. There was no indication of strong effects from a spring patch burn on grasshoppers, when the most abundant grasshopper species would have been in the egg stage. Although a few grasshopper species overwinter as nymphs, these species were not dominant in these pastures. By contrast, fall patch burning negatively affected grasshopper population densities but there was little evident impact of patch grazing. The examination of species diversity metrics was constrained by the low replication in the study, but the effects of cattle grazing on grasshopper populations appeared smaller than patch burning.
    96th ESA Annual Convention 2011; 08/2011
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    Richard C Waterman, Lance T Vermeire
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    ABSTRACT: Complete rest or grazing deferment is a general recommendation to encourage vegetative recovery following fire in the western United States. However, effects of grazing deferments on animal performance have not been determined. Prescribed fires were individually applied to nine separate, 1.5-ha pastures each year (2006 and 2007) for a total of 18 pastures. Grazing was deferred until spring (16 May), early summer (19 June), or late summer (1 August) the growing season after fire. At the end of each deferment, a 70-d (2007) or 41-d (2008) grazing period was initiated. Stocking rates were consistent between treatments within year, but were adjusted between years to achieve the targeted residual biomass of approximately 300 kg ? ha 21 . Diet quality was assessed approximately every 15 d throughout each grazing period (three pastures ? period 21) via collection of rumen extrusa throughout the 2-yr study. Ewe body weight was measured on and off-test for each grazing period. Diet extrusa samples for in vitro organic matter disappearance was less (P 5 0.03) for late summer than early summer grazing periods and equal to the spring period (62.9, 64.6, and 61.0 6 0.90%, respectively for spring, early summer, and late summer grazing periods). In vitro neutral detergent fiber disappearance decreased (P 5 0.01) by 10.6 percentage units from early grazing to late grazing period in 2007, whereas no differences were observed in 2008. Ewe average daily gain did not differ between spring and early summer grazing periods and were greater (P 5 0.03) than the negligible body weight gains of the late summer grazing period. Total gain was 10.9 kg ? ha 21 greater in 2008, and a quadratic response was measured for grazing period in 2007. Results indicate that deferment until early summer may be preferable so that stocking rates can be more accurately determined and animal performance is not diminished. Resumen El descanso o diferimiento del pastoreo es una recomendación común para fomentar la recuperación vegetativa después de la aplicación de fuego en el oeste de Estados Unidos. Sin embargo, no se han determinado los efectos del diferimiento de pastoreo en la performance animal. Se aplicaron quemas prescriptas individualmente a 9 potreros de 1.5-ha cada añ o (2006 y 2007) sumando un total de 18 pasturas. El pastoreo se difirió hasta la primavera (16 de mayo), principios de verano (19 de junio), o a finales del verano (1 de agosto) de la temporada de crecimiento posterior a la quema. Al final de cada diferimiento, se inició un período de pastoreo de 70-d (2007) o 41-d (2008). La carga animal fue consistente entre los tratamientos dentro de cada añ o, pero fueron ajustadas entre añ os para lograr una biomasa residual de aproximadamente 300 kg ? ha 21 . La calidad de la dieta se evaluó aproximadamente cada 15 d a lo largo de cada período de pastoreo (3 potreros ? período 21) a través de la recolección de extrusa ruminal durante los dos añ os del estudio. El peso corporal de las ovejas (PC) fue medido dentro y fuera de la prueba para cada período de pastoreo. Las desaparición de la materia orgánica in vitro de las muestras de extrusa ruminal fue menor (P 5 0.03) para el período de pastoreo de finales de verano comparado con el de comienzos de verano e igual al período de primavera (62.9, 64.6 y 61.0 6 0.90%, para la primavera, principios de verano y finales del verano, respectivamente). La desaparición in vitro de fibra detergente neutro disminuyó (P 5 0.01) en 10,6 unidades porcentuales desde comienzos a finales del período pastoreo en 2007, mientras que no se observaron diferencias en 2008. El promedio de ganancia diaria de las ovejas en los períodos de pastoreo de primavera y comienzos del verano no fue diferente pero fue mayor (P 5 0.03) que las ganancias de peso de cuerpo despreciables obtenidos durante el pastoreo de finales de verano. La ganancia de peso total fue mayor en 10.9 kg ? ha 21 en 2008 y una se detectó una respuesta cuadrática al período de pastoreo en 2007. Los resultados indican que el diferimiento hasta principios del verano puede ser preferible para poder determinar la carga animal con más exactitud y para que el rendimiento animal no se vea disminuido.
    Rangeland Ecology & Management 01/2011; 64(1). DOI:10.2307/25835898 · 1.46 Impact Factor
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    Lance T. Vermeire, Jessica L. Crowder, David B. Wester
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    ABSTRACT: Fire is an important process in many ecosystems, especially grasslands. However, documentation of plant community and soil environment responses to fire is limited for semiarid grasslands relative to that for mesic grasslands. Replicated summer fire research is lacking but necessary because summer is the natural fire season and the period of most wildfires in the western United States. We evaluated summer fire effects on soil temperature, soil moisture, aboveground biomass, root biomass, and functional group composition for 2 yr in semiarid C₃-dominated northern Great Plains. Following pre-treatment measures, four 0.75-ha sites were burned during August for comparison with nonburned sites, and the experiment was repeated the next year on adjacent sites to assess weather effects. Soils were about 0.5°C cooler on burned sites in the first experiment and similar in the second. Burned sites were consistently 1% drier than nonburned sites. Litter was reduced by fire but did not account for changes in soil moisture because differences occurred before the growing season. Current-year aboveground biomass and root biomass were similar between treatments, indicating productivity was resistant to summer fire. Perennial C₃ grasses increased in dominance because of positive biomass responses to fire for all but the bunchgrass, Hesperostipa comata, and a reduction of annual grasses. Perennial C₄ grasses were unaffected by summer fire. H. comata was resilient, with biomass on burned sites equaling nonburned sites the second growing season. Biomass was more responsive to precipitation than fire, and the fire-induced changes in species composition suggest exclusion of fire may be a greater disturbance than summer fire. El fuego es un proceso importance en muchos ecosistemas, especialmente en praderas. Sin embargo, la documentación de respuestas de la comunidad vegetal y del ambiente edáfico al fuego en pastizales semiáridos es limitada comparado con praderas mesofíticas. Ensayos replicados investigando los fuegos de verano son escasos pero necesarios dado que el verano es la estación natural de ocurrencia de la mayoría de los incendios en el oeste de los Estados Unidos. Evaluamos los efectos de quemas de verano sobre la temperatura del suelo, la humedad del suelo, la biomasa aérea, la biomasa radicular, y la composición de grupos funcionales durante dos años en pastizales semiáridos dominados por especies C₃ en el norte de las Grandes Planicies de América del Norte. Luego de mediciones pre-experimentales, cuatro sitios de 0,75 ha fueron quemados durante el mes de Agosto para compararlos con sitios que no fueron quemados y el experimento se repitió al año siguiente en sitios adyacentes para evaluar efectos meteorológicos. Los suelos de los sitios quemados estuvieron 0,5°C más frescos en el primer experimento y de modo similar en el segundo. Los sitios quemados estuvieron consistentemente 1% más secos que los sitios no-quemados. El fuego redujo la cantidad de broza, pero la misma no explicó las diferencias en humedad edáfica porque dichas diferencias ocurrieron antes de la estación de crecimiento. El crecimiento del año de biomasa aérea y la biomasa radicular fue similar entre tratamientos, indicando que la productividad resistió el fuego de verano. Los pastos perennes C₃ aumentaron en dominancia debido a respuestas positivas al fuego en producción de biomasa para todas las especies excepto el pasto Hesperostipa comata, y una reducción en las especies anuales. Los pastos perennes C₄ no fueron afectados por los fuegos de verano. H. comata demostró resiliencia con biomasas iguales en sitios quemados y no-quemados en la segunda estación de crecimiento. La biomasa respondió más a la precipitación que al fuego y los cambios en la composición de especies inducida por el fuego sugieren que la exclusión del fuego podría ser un disturbio mayor que los fuegos de verano.
    Rangeland Ecology & Management 01/2011; 64(1):37-46. DOI:10.2307/25835900 · 1.46 Impact Factor
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    ABSTRACT: Auxinic herbicides, such as 2,4-D and dicamba, that act as plant growth regulators are commonly used for broadleaf weed control in cereal crops (e.g., wheat, barley), grasslands, and noncroplands. If applied at late growth stages, while cereals are developing reproductive parts, the herbicides can reduce seed production. We tested whether growth regulators have this same effect on the invasive annual grass Japanese brome. The herbicides 2,4-D, dicamba, and picloram were applied at typical field use rates to Japanese brome at various growth stages in a greenhouse. Picloram reduced seed production nearly 100% when applied at the internode elongation, boot, or heading stages of growth, whereas dicamba appeared to be slightly less effective and 2,4-D was much less effective. Our results indicate it may be possible to control Japanese brome by using growth regulator herbicides to reduce its seed production, thereby depleting its short-lived seed bank. Nomenclature: 2,4-D; dicamba; picloram; Japanese brome, Bromus japonicus Thunb.; barley, Hordeum vulgare L.; wheat, Triticum aestivum L.
    Invasive Plant Science and Management 03/2010; 3(March-May):12-16. DOI:10.1614/IPSM-D-09-00007.1 · 0.84 Impact Factor
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    ABSTRACT: Se sabe que el forraje que crece después de fuego es un fuerte atrayente para los grandes herbívoros. Sin embargo, el fuego generalmente ha sido evitado como una herramienta de distribución del apacentamiento por temor a provocar una sobreutilización localizada de los recursos forrajeros. Nuestros objetivos fueron examinar si la utilización del forraje fue afectada por la época de la quema, determinar la preferencia del ganado por los sitios quemados en relación a los sitios sin quemar, determinar la respuesta de las hierbas a la quema en parches y describir las relación entre la biomasa en pie al final de la estación y la distancia de los sitios quemados. 16 parcelas de 4 ha fueron quemadas a mediados de Noviembre o a mediados de Abril y quedaron expuestas al apacentamiento por el ganado durante la estación de crecimiento. Los tratamientos de quema fueron bloqueados dentro los potreros para permitir que hatos individuales tuvieran acceso a los sitios quemados en otoño, primavera y no quemados. En Septiembre, mediante corte, se hicieron estimaciones de la biomasa en pie de zacates, hierbas y del forraje total, las cuales se efectuaron en los sitios quemados y a 50, 100, 200, 400 y 800 m de distancia del limite de la parcelas quemada. La biomasa en pie también fue muestreada en exclusiones en los sitios quemados y sin quemar. El ganado no mostró preferencia por alguna de las épocas de quema, pero fue fuertemente atraído por los sitios quemados, reduciendo en 78% la biomasa en pie dentro de los sitios quemados comparado con una reducción del 19% fuera del área de influencia de la quema. La biomasa en pie de los zacates disminuyó en una manera predecible con la proximidad de las parcelas quemadas. Las hierbas se incrementaron en 60% a 1,095 kg ha−1 en las parcelas quemadas apacentadas, pero no fueron afectadas por la distancia a partir de la quema. La quema en parches puede ser empleada como herramienta efectiva y barata de distribución del apacentamiento.
    Rangeland Ecology & Management 09/2009; DOI:10.2111/1551-5028(2004)057[0248:PBEOGD]2.0.CO;2 · 1.46 Impact Factor
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    ABSTRACT: Los saltamontes (Orthoptera: Acrididae) son considerados entre las plagas mas dañinas de los pastizales, pero son indispensables para la sobrevivencia de muchas especies de fauna silvestre. La mayoria de las especies de saltamontes son inofensivas, pero el control con insecticides es no discriminatorio entre estas especies. Los objetivos fueron evaluar los efectos de la quema prescrita sobre la abundancia y biomasa de saltamontes asi como determinar si las especies podrian ser selectivamente controladas con la quema prescrita. Veinticuatro sitios de 4 ha fueron selecionados en una pradera mixta de sand sagebrush cercana a Woodward, Okla. y fueron bloqueados por potrero. Las parcelas recibieron aleatoriamente los siguientes tratamientos: quema de otoño, quema de primavera y sin quema dentro de cada bloquedo con 4 repeticiones por tratamiento por cada 2 años. La biomasa y abundancia de los saltamontes fue muestreada a finales de Julio y a principios de Agosto barriendo con redes de lienzo. Los especimenes fueron pesados al cercano 0.1 mg e identificados a nivel de especie. Los tratamientos con fuego no tuvieron efecto sobre la abundancia y biomasa total entre especies, con 10 saltamontes pesando 4,090 mg por cada 150 barridas. El resultado de los tratamientos con fuego fue variable entre las 4 mas comunes especies y esto puede ser explicado por la biologia de los insectos. Melanoplus bowditchi y M. flavidus no fueron afectadas por el fuego. Hesperotettix viridis fue sensitiva, siendo reducida alrededor de un 88% debido al daño de recibido por las plantas hospedadoras en ambas temporadas. La abundancia de Ageneotettix deorum fue 65% mas baja en las parcelas con quema de otoño. Nosotros hipotetizamos que la reduccion ocurrio debido a que las especies depositan sus huevos sobre la superficie del suelo y por lo tanto estan expuestas al calor del fuego. Prescripciones para el uso del fuego pueden ser desarrolladas par las especies objetivo tomando en cuenta las vulnerabilidades especificas de las especies y de esta forma reducir las especies de saltamontes plaga mientras se mantiene disponibilidad de alimento para las especies depredadoras de saltamontes.
    Rangeland Ecology & Management 09/2009; 57(Jan 2004):29-33. DOI:10.2111/1551-5028(2004)057[0029:SCORGW]2.0.CO;2 · 1.46 Impact Factor
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    ABSTRACT: Precipitation-use efficiency (PUE) is a key determinant of aboveground net primary production (ANPP). We used long-term datasets to contrast ANPP and PUE estimates between northern (southeast Montana) and southern (north Texas) mixed-grass prairies. Effects of varying amounts and temporal distribution of precipitation on PUE were examined at the Montana site, using a rainout shelter and irrigation. Results show that 1) ANPP was 21% less in Montana than Texas (188 g·m-2 vs. 237 g·m-2); 2) plant function type (PFT) composition varied between the two study locations, with cool-season perennial grasses (CSPG) dominating in Montana (52%) and warm-season perennial grasses (WSPG) dominating in Texas (47%); 3) production dynamics varied between the two sites with 90% of ANPP completed by 1 July in Montana as compared to 31 August in Texas; 4) average PUE estimates were greater in Montana (0.56 g dry matter·m-2·mm-1 of precipitation) than Texas (0.40 g·m-2·mm-1); and 5) contributions to PUE estimates varied among PFT and location, with CSPG estimates being greater in Montana than Texas (52% vs. 31%) and WSPG estimates being greater in Texas than Montana (47% vs. 27%). Seasonal droughts and supplemental irrigations at the Montana site substantially altered ANPP, PFT biomass composition, and PUE. Results show PUE was responsive to PFT composition relative to amount and seasonal distribution of precipitation. Therefore, one should expect changes in ANPP and PUE to occur with shifts in precipitation patterns until PFT composition becomes adjusted to the regime.
    Rangeland Ecology & Management 05/2009; 62(3). DOI:10.2111/07-140R2.1 · 1.46 Impact Factor