Gutierrezia Sarothrae Research Articles

The Essential Oil Compositions of Ambrosia acanthicarpa Hook., Artemisia ludoviciana Nutt., and Gutierrezia sarothrae (Pursh) Britton & Rusby (Asteraceae) from the Owyhee Mountains of Idaho.

As part of our interest in the volatile phytoconstituents of aromatic plants of the Great Basin, we have obtained essential oils of Ambrosia acanthicarpa (three samples), Artemisia ludoviciana (12 samples), and Gutierrezia sarothrae (six samples) from the Owyhee Mountains of southwestern Idaho. Gas chromatographic analyses (GC-MS, GC-FID, and chiral GC-MS) were carried out on each essential oil sample. The essential oils of A. acanthicarpa were dominated by monoterpene hydrocarbons, including α-pinene (36.7-45.1%), myrcene (21.6-25.5%), and β-phellandrene (4.9-7.0%). Monoterpene hydrocarbons also dominated the essential oils of G. sarothrae, with β-pinene (0.5-18.4%), α-phellandrene (2.2-11.8%), limonene (1.4-25.4%), and (Z)-β-ocimene (18.8-39.4%) as major components. The essential oils of A. ludoviciana showed wide variation in composition, but the relatively abundant compounds were camphor (0.1-61.9%, average 14.1%), 1,8-cineole (0.1-50.8%, average 11.1%), (E)-nerolidol (0.0-41.0%, average 6.8%), and artemisia ketone (0.0-46.1%, average 5.1%). This is the first report on the essential oil composition of A. acanthicarpa and the first report on the enantiomeric distribution in an Ambrosia species. The essential oil compositions of A. ludoviciana and G. sarothrae showed wide variation in composition in this study and compared with previous studies, likely due to subspecies variation.

Exploration of Phenolic Content and Antioxidant Potential from Plants Used in Traditional Medicine in Viesca, Mexico

The medicinal plants of the desert can be a potential source of natural bioactive compounds with applications in health and food preservation. This work aimed to investigate the phenolic content and antioxidant potential of twenty-three plants from the arid zone of Viesca, Mexico. The antioxidant potential was determined by three methods (ABTS, FRAP, and DPPH). Two extraction methods and three different concentration levels (1:10 mg/mL, 1:25 mg/mL, and 1:50 mg/mL) were evaluated. According to the results, Turnera diffusa (Damiana), Gutierrezia sarothrae (Hierba de San Nicolas), and Leucophyllum frutescens (Cenizo) present the largest content of phenolic compounds and high antioxidant activity. The highest values of antioxidant activity were achieved using a solid/liquid ratio of 1:50 g/mL for T. diffusa and G. sarothrae and 1:25 mg/mL for L. frutescens. The maceration method was the most suitable for extracting antioxidant compounds from T. diffusa and L. frutescens, while ultrasound-assisted extraction was more efficient for G. sarothrae. The HPLC-MS analysis showed the presence of important phenolic compounds. This study shows for the first time that three plants that naturally grow in Viesca have great potential as a source of natural antioxidant compounds.

Effects of Precipitation and Livestock Grazing on Foliage Foraging Ants in a Chihuahuan Desert Grassland

We examined the relationship between seasonal livestock grazing (late summer and late winter) and the abundance of two ant species, Dorymyrmex insana and Forelius pruniosus, on three types of plants (mesquite shrubs, snakeweed sub-shrubs, and mixed grasses) dominated by black grama (Bouteloua eriopoda). Stocking rates were adjusted to remove 75% of the available forage. Since Chihuahuan Desert grasslands are not in transition to shrublands, the grasses and some herbaceous plants are the only available forage. We hypothesized that neither rainfall nor cattle grazing would affect the abundance of these ants on mesquite (Prosipis glandulosa) or snakeweed (Gutierrezia sarothrae). Linear regressions of monsoon rainfall on mesquite (Prosopis glandulosa) produced an r2 nearly equal to that with the annual precipitation. Monsoon rainfall on the evergreen sub-shrub, Gutierrezia sarothrae, resulted in June-July rainfall accounting for 47% - 83% of the variation in densities of D. insana on snakeweed. The number of D. insana was more than double the number of F. pruinosus on grasses, mesquite, and snakeweed. There were significant reductions in the abundance of F. pruinosus on the grass in the grazed plots; each year the plots were grazed. There were no significant effects of grazing on the abundance of either of the ant species sampled from G. sarothrae canopies. There were significantly fewer D. insana on mesquite in summer grazed plots than on P. glandulosa in winter grazed and ungrazed plots in the second and third years of grazing. Pre-grazing effects were compromised by the high annual (more than double) precipitation.

Diterpenoids from Gutierrezia sarothrae and G. microcephala: Chemical diversity, chemophenetics and implications to toxicity in grazing livestock

Broom snakeweed (Gutierrezia sarothrae) and threadleaf snakeweed (G. microcephala) are suffrutescent plants found in many parts of western US rangelands and are possibly toxic to grazing livestock. The toxic components are not known, but it has been suggested that the diterpene acids may be both toxic and abortifacient. One hundred sixty-two samples of snakeweed were collected from 55 locations in Colorado, Oklahoma, New Mexico, Texas, Wyoming and Utah and were taxonomically classified. Samples were analyzed by GC-MS in a chemophenetic analysis and grouped into individual chemotypes based on diterpene acid content. The GC-MS profiles were found to be diverse showing at least eight different chemotypes. From each of the chemotypes the major diterpene acids were isolated and characterized by IR, MS and NMR spectroscopy. Twenty-one diterpenoids were identified and found to be a mix of furano, lactone, di-acid and esters of labdane, ent-labdane and chlerodane acids and alcohols. Only four of the 21 compounds isolated had been previously reported as occurring in G. sarathorea or G. microcephala, while another eight compounds were previously reported from other Gutierrezia or related species. Nine of the isolated diterpenoids have not been previously reported and their structure elucidation is reported.

Differential Species Responses to Aspects of Resistance to Invasion in Two Columbia Plateau − Protected Areas

Protected-area sagebrush steppe ecosystems are few in number and increasingly important to the North American conservation network as sagebrush steppe faces growing threats from land use, climate change, and invasive species. We analyzed the distribution and abundance of native perennial and invasive annual plants to better understand patterns of plant invasion within two protected areas: John Day Fossil Beds National Monument (JODA), located in central Oregon, and Craters of the Moon National Monument and Preserve (CRMO), located in southeast Idaho. We used multivariate analysis to examine vegetation monitoring datasets and illuminate geographic variation in plant cover along gradients of well-known aspects of resistance to plant invasion (elevation, exposure [slope and aspect], precipitation and proximity to disturbance). Topographically mediated resistance to invasion appeared to manifest in the park with greater topographic variability (JODA), while increased elevation was more strongly associated with resistant sites in the park, which spanned a greater elevational gradient (CRMO). Factors that may mitigate moisture-mediated resistance also differed between sites. Slope and aspect were factors of apparent resistance for bunchgrass communities in JODA, while high crop year precipitation appeared to benefit medusahead (Taeniatherum caput-medusae [L.] Nevski) and the weedy native subshrub broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) over bunchgrasses and Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young). Increased elevation and distance to disturbed areas were the most important factors of resistance in forb-rich communities at CRMO, with the invasive annuals cheatgrass (Bromus tectorum L.), tumblemustard (Sisymbrium altissimum L.), and Descurainia spp. Webb & Bethel. invading in low elevations and in close proximity to roads or agricultural fields. Such complexity underscores the idiosyncratic nature of the manifestation of resistance and the need for place-based empirical studies to provide information for guiding protected-area management.

Long-Term Persistence of Cool-Season Grasses Planted to Suppress Broom Snakeweed, Downy Brome, and Weedy Forbs

Invasive plants are spreading throughout arid and semiarid rangelands of western North America. Long-lived perennial plants that can persist under harsh environmental conditions are needed to compete with invasive species. The objective of this study was to conduct a long-term evaluation of native and introduced grass species planted to suppress and prevent reinvasion of downy brome (Bromus tectorum L.), snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby), and annual forbs. Seeding treatments comprised three introduced grasses: crested wheatgrass (Agropyron cristatum [L.] Gaertner × A. desertorum [Fisch. Ex Link] Schultes), pubescent wheatgrass (Elytrigia intermedia spp. trichophorum [Host] Beauv.), and Russian wildrye (Psathyrostachys junceus [Fisch.] Nevski); a mix of these introduced grass species, three native grasses: bluebunch wheatgrass (Pseudoroegneria spicata [Pursh]), western wheatgrass (Pascopyrum smithii [Rybd.] A. Löve), and squirreltail (Elymus multisetus [J.G. Sm.] Jones); and a mix of these native grass species, or forage kochia (Bassia prostrata [L.] A.J. Scott). The treatments were seeded in October 2003. Frequency and biomass were measured in 2015 and 2017 in Howell, Utah and in 2015 and 2016 in Nephi, Utah. Crested wheatgrass persisted at both locations (> 62% frequency) along with the rhizomatous grass species, pubescent (> 65%) and western wheatgrasses (> 72%). Russian wildrye was still present at Howell (30%) with little remaining at Nephi (7%). Squirreltail frequency was 13% at Howell and 12% at Nephi. Bluebunch wheatgrass was no longer present at either location (< 1%). Forage kochia remained at Nephi (36%) with little remaining at Howell (4%). Downy brome was present at both locations and was suppressed relative to control plots, at Nephi, by crested wheatgrass and the introduced grass mix (< 9%). Downy brome was > 93% in all plots, at Howell, in 2017. In summary, crested, pubescent, and western wheatgrasses were able to persist over 12 yr at both locations.

Impact of Climate Change on Livestock Returns and Rangeland Ecosystem Sustainability in the Southwest

Climate change will increase variability in temperature and precipitation on rangelands, impacting ecosystem services including livestock grazing. Facing uncertainty about future climate, managers must know if current practices will maintain rangeland sustainability. Herein, the future density of an invasive species, broom snakeweed, is estimated using a long-term ecological dataset and climate projections. We find that livestock stocking rates determined using a current method result in lower forage production, allowable stocking rate, and grazing value than an economically efficient stocking rate. Results indicate that using ecology and adaptive methods in management are critical to the sustainability of rangelands.

Influence of Land-Use Legacies Following Shrub Reduction and Seeding of Big Sagebrush Sites

Big sagebrush (Artemisia tridentata Nutt.) plant communities often require management to reduce shrub density and rehabilitate understory vegetation. We studied vegetation responses to a two-way chain harrow treatment and broadcast seeding of 12 herbaceous species at eight Wyoming big sagebrush (A. tridentata Nutt. subsp. wyomingensis Beetle & Young) sites. These sites differed in land-use history; five were cultivated for dryland wheat production during the 1950−1980s and then seeded with introduced forage grasses (C-S), while three had not been exposed to this land-use legacy (non C-S). Our objective was to evaluate whether the C-S legacy influences the magnitude of vegetation change following contemporary treatment. Before treatment, C-S sites had lower sagebrush cover, higher dead sagebrush cover, and higher broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) cover than adjacent non C-S sites. Plant community change 3 years after treatment, determined with multivariate ordination analysis of species composition, varied between site histories, and response to treatment was most strongly correlated with reductions in sagebrush cover, increases in perennial grasses, and increases in 10 other herbaceous species—including some undesirable species and four that were seeded in 2010. Five years after treatment, mature sagebrush cover remained reduced for both land-use histories, yet density of sagebrush seedlings and broom snakeweed increased in C-S sites during the second and third years after treatment. In addition, perennial forb cover increased for C-S sites, while perennial grass biomass increased for non C-S sites. Our results emphasize that broad variability in plant community responses to sagebrush reduction and seeding is possible within the same ecological site classification and that legacy effects due to the combination of past cultivation and seeding should be considered when planning restoration projects, including the consideration that seeding may not always be necessary on C-S sites.

Contrasting Effects of Long-Term Fire on Sagebrush Steppe Shrubs Mediated by Topography and Plant Community

The role of fire in restoration of sagebrush plant communities remains controversial mainly because of paucity of information from long-term studies. Here, we examine 15-year post-fire responses of big sagebrush (Artemisia tridentata ssp wyomingensis) and broom snakeweed (Gutierrezia sarothrae), the two most abundant native shrubs at the John Day Fossil Beds National Monument, a protected area in north-central Oregon, USA. Fire effects were studied along gradients of topography and community type through time post-burn. Community types were distinguished as brush, plots dominated by big sagebrush and woodland, plots with a significant presence of Western juniper (Juniperus occidentalis) trees. Fire reduced big sagebrush cover in brush plots up to 100% and in woodland plots up to 86%. Broom snakeweed cover declined by 92% and 73% in brush plots and woodland plots, respectively. Big sagebrush did not show signs of recovery 15 years after burning regardless of topography and community type while broom snakeweed populations were clearly rebounding and prospering beyond pre-burn levels. Our results showed that an area initially dominated by big sagebrush (cover of big sagebrush 10-20%, cover of broom snakeweed 2-4%) dramatically shifted to an area dominated by broom snakeweed (cover of big sagebrush <1%, cover of broom snakeweed 5%) in brush-dominated plots. Our results indicated that brush-dominated plots at lower elevation and southern exposures are the least post-fire resilient. We also observed a declining population of big sagebrush on unburned areas, suggesting the lack of post-fire recovery on burned areas was perhaps a result of low seeding potential by extant populations. Although more years of observation are required, these data indicate that recovery time, the encroachment of opportunistic competing shrubs, and the initial condition of vegetation are essential considerations by land managers when prescribing fire in big sagebrush communities.

Biocrust carbon isotope signature was depleted under a C3 forb compared to interspace

Plants and biological soil crusts (biocrusts) are the key producers in drylands, but biocrusts seldom show net CO2 uptake. I hypothesized that biocrusts could augment CO2 fixation by incorporating plant-derived carbon. I collected biocrusts located at the base of Gutierrezia sarothrae (C3 forb), Bouteloua gracilis (C4 grass), and from bare interspaces between plants, and from a mesocosm experiment with live B. gracilis or dead B. gracilis roots. To trace carbon sources, I determined 13C values of the biocrust community, isolated cyanobacteria and lichen, and plant leaves because the photosynthetic pathway distinguishes the tissue 13C values. Biocrust communities and washed cyanobacteria and cyanolichen in G. sarothrae microsites were depleted by ~2‰ relative to other locations. Biocrust δ13C did not differ between the interspace and live or dead B. gracilis. Potential mechanisms for the trend in biocrust δ13C adjacent to C3 plants include differences in microsite conditions, biocrust communities, use of respired CO2 in the soil matrix for photosynthesis, or mixotrophic use of plant photosynthates. Further investigation of this observation may improve understanding of the degree to which the activities of dryland primary producers are coupled.

Caracterización del hábitat de Amoreuxia wrightii (Bixaceae), una especie en peligro de extinción en el noreste de México

Antecedentes y Objetivos: En México, Amoreuxia wrightii se encuentra en estatus de peligro de extinción de acuerdo a la NOM-059-SEMARNAT-2010. En este estudio se realizó la caracterización de poblaciones naturales de A. wrightii, mediante un análisis de la flora asociada y las propiedades físicas y químicas de los suelos donde se desarrollan en dos comunidades contrastadas desde el punto de vista de la cobertura del dosel en el matorral tamaulipeco en el noreste de México.Métodos: En 2014 se establecieron 10 sitios de muestreo en dos ambientes diferenciados por la estructura de la vegetación: cinco sitios en asociaciones vegetales con cobertura vegetal densa y cinco sitios en áreas perturbadas con suelo desnudo. En cada área se evaluó la estructura vegetal y variables edáficas y se realizó un Análisis de Correspondencia Canónica.Resultados clave: De acuerdo a la relación con otras especies, A. wrightii se asoció con especies pioneras, que emergen después de un disturbio, con el dominio de pastos como Aristida purpurea, Cenchrus ciliaris, Cynodon dactylon, Panicum obtusum, especies de herbáceas Gutierrezia sarothrae, Gymnosperma glutinosum y Parthenium hysterophorus, así como arbustos de porte bajo como Acacia amentacea, A. berlandieri y Eysenhardtia texana. De acuerdo con las variables edáficas, se observó que A. wrightii prefiere suelos arcillosos y limosos, con suelos con pH ligeramente alcalinos y con densidad aparente alta. Ningún individuo de A. wrightii fue registrado en sitios que presentaron suelos con altos contenidos de arena y altos contenidos de materia orgánica.Conclusiones: Amoreuxia wrightii fue más abundante en áreas con nula cobertura, desprovistas de vegetación, sobre suelos con bajo contenido de materia orgánica y altos contenidos de pH, limo, arcilla y densidad aparente. De acuerdo a la relación con otras especies, se asoció con especies pioneras, que emergen después de un disturbio.

Broom snakeweed (Gutierrezia sarothrae) Population Change in Central New Mexico: Implications for Management and Control

This paper examines changes in broom snakeweed populations (Gutierrezia sarothrae [Pursh] Britt. & Rusby) from 1979 to 2014 at three prairie grassland sites in New Mexico. Data gathered each fall were used to study broom snakeweed population dynamics and to estimate the probability that the relatively short-lived subshrub will die off or invade blue grama (Bouteloua gracilis [H.B.K. Lag]) rangelands. Annual broom snakeweed standing crop data were used to categorize populations as None (<100 kg ha−1), Light (<300), Moderate (<750), or Heavy (≥750). Ordered logit regression was then used to estimate the frequency of transition between these categories over time depending on environmental and site factors. Significant variables found to influence annual variation in broom snakeweed included the broom snakeweed standing crop and density observed the previous period (+ effect for continued broom snakeweed); grass standing crop the previous period (−); rainfall received from April to June (+); and average temperatures during April (+) and June (−). The probability of broom snakeweed invading an area that is currently without the plant ranges from about 1% to > 40% depending on environmental conditions and the amount of grass standing crop present. Transition probability estimates were also used in a Monte Carlo simulation model to evaluate the economics of broom snakeweed control. The economics of chemical broom snakeweed control were most strongly related to the rate of snakeweed reinvasion on treated areas and to the probability of natural die-off if infested areas were not sprayed.

Smoke Water and Heat Influence Emergence of Shortgrass Prairie Species

Exposure to smoke can influence the germination of seeds in many fire-prone ecosystems, but this effect is not well studied in grasslands. Smoke treatments such as smoke water could be useful as management and restoration tools if the response of target species in natural settings is well understood. We tested eight species native to the southern High Plains region in Texas, USA, that were already known to respond to smoke water in the laboratory, for their responses in a less controlled glasshouse environment. We exposed seeds to smoke water, heat, or a combination of the two, sowed them into greenhouse flats, and observed and recorded emergence. Emergence of nearly all species was influenced by smoke water, with most species experiencing either lower emergence or longer times for emergence when exposed to high-concentration smoke water. Smoke water exposure enhanced emergence of broom snakeweed (Gutierrezia sarothrae [DC.] A. Gray) seeds, with more than twice as many treated seeds emerging than untreated seeds (germination of control seeds = 26 % ± 4.39 % SE; germination of treated seeds = 69 % ± 4.62 % SE). Because many species displayed different results in the glasshouse as compared to the laboratory, smoke treatments should be tested in the field before being used on a larger scale. Doing so will allow a better understanding of how target species might respond to smoke treatments with more realistic soils, fluctuating temperatures, and other complications encountered in the field.

New Antiplasmodial Diterpenes from Gutierrezia Sarothrae

Bioassay guided fractionation of the MeOH extract of the plant Gutierrezia sarothrae (Asteraceae) using an assay for antiplasmodial activity against the drug-resistant Dd2 strain of Plasmodium falciparum led to the isolation of the two new diterpenes 3α-angeloyloxy-15-hydroxylabda-7,13-dien-16,15-olid-18-oic acid (1) and 3α-angeloyloxy-15-methoxylabda-7,13-dien-16,15-olid-18-oic acid (2). The structures of 1 and 2 were elucidated by interpretation of 1D and 2D NMR spectroscopic data, mass spectrometry, and comparison with the data of related compounds reported in the literature. Compound 1 exhibited moderate antiplasmodial activity with an IC50 values of 10.4 ± 4.3 μM.

No Long-Term Effects of Prescribed Fire on Lehmann Lovegrass (Eragrostis lehmanniana)–Invaded Desert Grassland

AbstractDesert grasslands of the southwestern United States have experienced an increase in the abundance and distribution of woody plant species over the past century. Shrub encroachment has caused a substantial loss of grasslands in the northern Chihuahuan Desert. The Chihuahuan Desert has also been invaded by Lehmann lovegrass, a fire-adapted species from southern Africa. In 1999, the U.S. Department of Agriculture–Agricultural Research Service burned a remnant desert grassland to determine the effects of prescribed fire on shrub–perennial grass dynamics. The grassland also contained the nonnative perennial grass Lehmann lovegrass. I am reporting on a study that was initiated to determine whether prescribed burning would alter the vegetative community within and proximal to a Lehmann lovegrass–dominated patch. Cover of Lehmann lovegrass showed no significant response to the burn treatment. Of the dominant native species, only black grama and broom snakeweed had a significant year by treatment interaction. No species or growth form had a significant vegetation type by year by treatment interaction. After 6 yr, differences between burned and unburned transects were not significant for any species or growth form.

Unraveling landscapes with phytogenic mounds (nebkhas): An exploration of spatial pattern

Phytogenic mounds (nebkhas) often are symptoms of desertification in arid regions. Interactions among nebkhas and between nebkhas and their environment are however poorly examined. To this end, three main hypotheses of nebkha pattern formation were evaluated in this study. These state that nebkha patterns are either shaped by: (i) biologically induced recruitment inhibiting zones, (ii) biologically induced recruitment encouraging zones, or (iii) by the spatial distribution of abiotic factors which are not biologically driven. Contrasting nebkha landscapes were examined: a highly dense New Mexican mesquite (Prosopis glandulosa) and snakeweed (Gutierrezia sarothrae and Gutierrezia microcephala) ecosystem, and a low-density mixed Tamarix aphylla and Calligonum comosum field in central Libya. Spatial second-order statistics of strategically chosen nebkha subpatterns were compared with those of null models in which observed patches were spatially randomized without overlap. Null model deviations were assessed with goodness-of-fit tests, and interpreted in terms of hypothesized mechanisms of nebkha pattern formation. Our results suggest that biologically induced recruitment inhibiting zones surround adult mesquite nebkhas. The configuration of Calligonum and Tamarix nebkhas may be driven by spatial dynamics of abiotic microsites which are not caused by nebkha interactions. Hence we conclude that both biotic and abiotic drivers can shape nebkha spatial patterns.

Rediscovery ofAztecacris gloriosus(Hebard, 1935) (Orthoptera: Acrididae): Associated Plants and Orthopterans, and an Attempted Intergeneric Copulation

After being unrecorded for approximately 70 years, Aztecacris gloriosus (Hebard, 1935) (Orthoptera: Acrididae) is documented from several sites in the Pajarito Mountains, Santa Cruz County, Arizona, USA. An association with Broom Snakeweed (Gutierrezia sarothrae) (Asteraceae) is suggested. The known range of the species is small and limited to Santa Cruz County. Habitat and associated orthopterans are discussed, as is an attempted mating by a male Melanoplus on a female A. gloriosus. Photos of A. gloriosus and its habitat are presented.

Smoke Water and Heat Shock Influence Germination of Shortgrass Prairie Species

Smoke or heat from fire can act as a cue that affects seed germination. We examined germination responses of 10 plant species (six forbs, two shrubs, two grasses) native to the southern High Plains in the United States, to smoke, heat, and their interaction in a laboratory experiment. Smoke treatments were applied by soaking seeds in 1∶5, 1∶10, or 1∶100 (v/v) Regen 2000® smoke solution for 20 h. Heat treatments were applied by placing seeds in an oven at 50°C or 80°C for 5 min. Nine species responded to smoke, heat, or both. Results showed that smoke can enhance, inhibit, or not affect seed germination. Germination capacities of Gutierrezia sarothrae (Pursh) Britton & Rusby and Astragalus crassicarpus Nutt. were promoted by 1∶5 and 1∶100 dilutions of smoke water, respectively; Coreopsis tinctoria Nutt., G. sarothrae, Salvia reflexa Hornem., Digitaria ciliaris (Retz.) Koeler, and Panicum virgatum L. were inhibited by high and/or moderate concentrations of smoke water either in germination percentage or in mean germination time. Germination percentage of Solanum elaeagnifolium Cav. increased following an 80°C heat treatment. Interaction effects between smoke and heat on germination also were detected. Smoke and heat treatments might be useful as management tools for promoting or suppressing specific target species of shortgrass prairie communities in future habitat management. El ahumado o calor del fuego puede actúa como agente que afecta la germinación de semillas. En un experimento de laboratorio, examinamos la respuesta de diez especies nativas (seis hierbas, dos arbustos, y dos pastos) de las Planicies del Sur de los Estados Unidos al ahumado, calor y las interacciones. En los tratamientos de ahumado se remojaron semillas con la solución de ahumado Regen 2000® en 1∶5, 1∶10, o 1∶100 (v/v) por 20 horas. Los tratamientos de calor se aplicaron poniendo semillas en un horno a 50°C o 80°C por 5 minutos. Nueve especies respondieron al ahumado, calor, o ambos. Los resultados mostraron que el ahumado podría mejorar, inhibir o no afectar la germinación. Las capacidades de germinación de la Gutierrezia sarothrae (Pursh) Britton & Rusby y Astragalus crassicarpus Nutt. fueron estimuladas por la dilución de 1∶5 y 1∶100 ahumador agua, respectivamente; Coreopsis tinctoria Nutt., G. sarothrae, Salvia reflexa Hornem., Digitaria ciliaris (Retz.) Koeler, y Panicum virgatum L. fueron inhibidas por alto y/o moderada concentración de ahumador agua en ambos porcetaje de germinación o en tiempo promedio de germinación. El porcentaje de germinación de Solanum elaeagnifolium Cav. aaumento después del tratamiento de calor a 80°C. Se detectaron efectos de interacciones entre ahumado y calor en la germinación. Los tratamiento de ahumado y calor podrían ser útiles como herramientas de manejo para promover o suprimir especies claves especificas de las comnidades de las praderas de pastos cortos en futuros manejos de hábitat.

Broom Snakeweed (Gutierrezia sarothrae): Toxicology, Ecology, Control, and Management

AbstractBroom snakeweed is a native weed widely distributed on rangelands of western North America. It often increases to near monocultures following disturbance from overgrazing, fire, or drought. This paper presents an up-to-date review of broom snakeweed toxicology, seed ecology, population cycles, succession, and management. The greatest ecological concern is that broom snakeweed displaces desirable forage for livestock or wildlife and greatly reduces biodiversity. It also is toxic and can cause abortions in all species of livestock. Propagation usually is pulse-driven in wet years, allowing large expanses of even-aged stands to establish and dominate plant communities. Snakeweed can be controlled by prescribed burning or spraying with herbicides. A weed-resistant plant community dominated by competitive grasses can prevent or minimize its reinvasion.

Estimating Grass Yield on Blue Grama Range From Seasonal Rainfall and Soil Moisture Measurements

To estimate annual forage production from moisture conditions it is important to consider the timing and seasonality of precipitation events as well as the past history of storm events. In this study we examined this relationship using 16 yr of annual measurements of herbaceous standing crop recorded at two study sites located on the Corona Range and Livestock Research Center in central New Mexico. Our hypothesis was that end-of-season herbaceous standing crop estimations could be improved using measured soil moisture instead of seasonal accumulations of rainfall as traditionally used for yield prediction. Daily recorded and simulated soil moisture levels were used to estimate the number of days over the growing season when soil moisture by volume was at low (< 20%), intermediate (20% to 30%), or high (≥ 30%) levels. Defining regression equations to include either simulated or probe-recorded measures of soil moisture improved the adjusted R2 of the regression models from 46% for the rainfall model to over 60% for various soil moisture models. Key variables for explaining annual variation in herbaceous production included seasonal moisture conditions, the amount of broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) present on the area, and the degree days of temperature accumulated over the growing season. Diurnal daily temperatures near historical averages were most advantageous for forage production. Simulated soil moisture data improved predictive grass yield estimates to a level equivalent to using onsite moisture probes to categorize daily moisture conditions. Potential exists to better predict forage conditions based on forecast information that uses soil moisture data instead of the traditional input of seasonal rainfall totals. Para estimar la producción anual de forraje basándose en las condiciones de humedad es importante tener en cuenta la época y la distribución de las precipitaciones, así como el pasado histórico de las mismas. En este estudio examinamos esta relación utilizando 16 años de mediciones anuales de la producción de la biomasa aérea en dos sitios localizados en el Corona Range and Livestock Research Center (CRLRC) en la parte central de New México. Nuestra hipótesis fue que las estimaciones al final de la época de crecimiento de la producción de biomasa aérea se pueden mejorar utilizando la humedad del suelo en lugar de la precipitación acumulada durante la estación como se ha utilizado tradicionalmente para la predicción de la producción. Niveles de humedad del suelo registradas y simuladas se utilizaron para estimar el número de días en la estación de crecimiento cuando la humedad del suelo por volumen es baja (< 20%), intermedia (20% a 30%) o alta (≥ 30%). Para definir la ecuación de regresión para incluir las medidas simuladas o las registradas de la humedad del suelo, mejoraron la RP2P ajustada de los modelos de regresión del 46% para el modelo de la precipitación a más de 60% para varios modelos de humedad del suelo. Las variables principales que se incluyeron para explicar la variación anual en la producción herbácea fueron, las condiciones de humedad estacional, la cantidad de escobilla (Gutierrezia sarothrae (Pursh) Britt. & Rusby) presente en el área y los días con grado de temperatura acumulada durante la estación de crecimiento. Las temperaturas diarias cercanas a los promedios históricos fueron las de más utilidad para producción de forraje. Los datos simulados de la humedad del suelo mejoraron las estimaciones del rendimiento de las gramíneas a un nivel equivalente al uso de sondas de humedad en el sitio para categorizar diariamente las condiciones de humedad. Existe la posibilidad de predecir mejor las condiciones de forraje, basándose en la predicción climática que usa datos de humedad en lugar de la medida tradicional de la precipitación total.