Hilaria Mutica Research Articles

The potential of laser-induced fluorescence (LIF) spectra of sheep feces to determine diet botanical composition

Laser-induced fluorescence (LIF) peaks near 470 nm (‘blue’) and 650 nm (‘red’) from sheep feces treated with chloroform (CHCl 3) displayed spectral signatures that varied with diet. Fecal samples were obtained rectally over 3 days in a replicated study consisting of four diets (treatments) fed to 16 Polypay and Polypay × Rambouillet lambs (four lambs per treatment). Basal diet consisted of tobosa ( Pleuraphis mutica Buckley [formally Hilaria mutica (Buckl.) Benth.] hay with 0% (control), 10%, 20% or 30% tarbush ( Flourensia cernua D.C.) added on a dry matter basis. Feces were dried at 60 °C, treated with chloroform and the extract from both crushed and intact fecal material was then excited by laser input at 355 nm. Tarbush leaves gave LIF only in the blue region of the spectrum. However, tobosa hay and all fecal pellets produced a bimodal LIF spectral distribution with a lower, broader peak feature in the blue region and a narrower well defined taller feature in the red region of the spectrum. Chloroform did not exhibit fluorescence peaks between 400 nm and 800 nm. As tarbush in the diet increased, so did the magnitude of counts in the blue region of the spectrum. The LIF red blue intensity ratios appear to be more reliable than actual counts in differentiating feces of sheep fed tobosa diets containing differing amounts of tarbush. red blue ratios decreased ( P < 0.05) linearly ( P < 0.005) for both crushed and intact sheep fecal pellets as the tarbush tobosa ratio in the diet increased. Inconsistencies in count amplitudes and wavelengths in either one or both regions (red or blue) of the spectrum and in red blue ratios (especially on Day 3 for crushed fecal samples) are discussed in terms of sample preparation procedures and sampling days. Our results suggest that further testing of the LIF technique is warranted using diets consisting of several species.

Tobosa Tiller Defoliation Patterns under Rotational and Continuous Stocking

Continuous low animal density grazing of tobosa [Hilaria mutica (Buckl.) Benth.] in the northern Chihuahuan desert results in nonuniform forage utilization. Stocking smaller tobosa rangeland paddocks with high numbers of cattle for short periods of time may facilitate more uniform forage utilization. Two grazing periods in each of 2 consecutive years were monitored to investigate the frequency with which tobosa tillers were defoliated and the intensity of defoliation (change in height) in relation to grazing pressure under high-density seasonal rotational and low-density seasonal continuous grazing. Approximately 40% of tiller height, including leaves, was removed at each defoliation in the rotational treatment, while intensity of defoliation per grazing event remained consistent. In the continuous treatment, amount of tiller removed varied widely and was not consistent among the 4 periods. Percentage of tillers defoliated in the rotational treatment was always greater than 75%, and always less than 30% in the continuous treatment. The probability that a tiller would be grazed at least once in the rotational treatment was more than twice as great as in the continuous treatment. However, within the rotational treatment, the probability of multiple grazing events (greater than or equal to 2) on an individual tiller was less than the probability of a tiller being grazed just once. In general, high-density rotation grazing promoted more uniform. forage utilization of tobosa than low-density continuous grazing.

Ecotone Dependent Recruitment of a Desert Shrub, Flourensia cernua, in Vegetation Stripes

In tropical semi-arid areas, a local concentration of water on sheet wash surfaces allows the persistence of densely vegetated stripes parallel to the contour lines, alternating with almost bare soil stripes. The boundaries of the vegetated stripes are, upslope, a colonization ecotone, and, downslope, a regressive ecotone, thus inducing a slow upwards displacement. This formation, recently described in the Chihuahuan Desert (Mexico), is known from Africa and Australia. Flourensia cernua is a dominant shrub species of the stripes whose distribution suggests that its population dynamics is strongly dependent on the upslope ecotone. The spatial restrictions to recruitment were determined analyzing the location of seedlings, young individuals and adults, and the grass cover (Hilaria mutica), in 10 two-meter-wide belts perpendicular to 5 stripes (...)

Protein Supplementation of Steers Grazing Tobosagrass in Spring and Summer

A 3-year study evaluated weight gain, blood urea nitrogen (BUN), and fecal nitrogen (FN) of beef steers fed 0.00, 0.34, or 0.68 kg/hd/day of cottonseed meal (41% CP) while grazing mesquite (Prosopis glandulosa var. glandulosa Torr.)/tobosagrass (Hilaria mutica [Buckl.] Benth.) range between April and July. Mixed breed beef steers (avg wt 230 kg) were allocated to three 6-pasture grazing cells and group-fed prorated amounts of supplement 3 days a week. Individual weights were recorded every 21 days. Crude protein in clipped forage samples remained above 7.0% except in July, 1985 (6.5%). Gain response varied among periods within year but the primary effects occurred in the first 40 to 60 days of grazing. In 1985, daily gains over 92 days were 0.38, 0.44, and 0.67 kg/hd/day for the 0.00, 0.34, and 0.68 kg supplement groups, respectively. In 1986 and 1987, daily gains during 85-day trials were 0.65, 0.66, and 0.71 kg/hd/day and 0.98, 1.08, and 1.07 kg/hd/day, respectively. Blood and feces were collected from 10 steers in each treatment group on each weigh date during the first 2 years. The 0.68 kg/hd/day supplement maintained higher (P<0.05) BUN and FN than the control group but response to 0.34 kg supplement was inconsistent. Performance and BUN data suggested that protein concentrate was not the appropriate supplement for steers grazing tobosagrass in the spring and summer.

Long-Term Effects of a 1969 Fire and Three 2,4,5-T Treatments on Prosopis glandulosa in Mitchell Co., Texas

Response of 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) treated mesquite (Prosopis glandulosa var. glandulosa Torr.) to prescribed fire was described by Britton and Wright (1971). Average mortality was 12% 1 year following spring burning and 26% after 5 years on this upland site (Wright et al., 1976). Honey mesquite is rarely killed by fires on bottomland sites in the Rolling Plains or on the High Plains (Wright and Bailey, 1982). Prescribed burns often are used to reduce live canopy cover of standing mesquite, burn down standing dead mesquite stems, and consume mesquite debris following mechanical treatment. Long-term effects of mesquite-control practices on stand structure are lacking in the literature. Our objective was to document mortality, basal area, and number of stems of marked mesquite plants over a 21-year period during which several brush-control treatments were applied. Earlier studies (Britton, 1970; Britton and Wright, 1971; Wright et al., 1976) focused on effects of fire on stand structure; the current study reports continued monitoring of individual mesquite trees. The study site was described by Britton (1970) and Britton and Wright (1971). It was located in the Texas Rolling Plains 33 km south of Colorado City, Texas (110*50'W, 32005'N) on Dalby (fine, mixed, thermic Typic Torrert) and Stamford (fine, montmorillonitic, thermic Typic Chromustert) clays (clay flats range site). Average annual precipitation was 50.3 cm with most resulting from late spring and late summer convection storms. Vegetation overstory is dominated by honey mesquite, with nearly pure stands of tobosagrass (Hilaria mutica [Buckl.] Benth.) in the understory. Common broomweed (Xanthocephalum dracunculoides DC. Shinners.) was common

Matric Potential of Clay Loam Soils on Arid Rangelands in Southern New Mexico

The matric potential of soil water is presented for 6 clay loam sites on floodplains of arid rangelands. Gypsum resistance blocks impregnated with plaster of paris were placed at 6 soil depths to 122 cm. At 4 locations, blocks were placed inside and outside a buried sheet metal cylinder so that estimates could be obtained of matric potential due to precipitation and due to precipitation plus run-in. The average annual precipitation during the approximate 20-year study period was 242 mm, slightly above the long-time average. Haplargids dominated by tobosa [Hilaria mutica (Buckl.)Benth.] had a greater probability of the matric potential greater than or equal to -1.5 MPa (wet soil) than the Calciorthids dominated by burrograss (Scleropogon brevifolius Phil.). The probability of matric potential greater than or equal to -1.5 MPa (wet soil) was as great or greater in winter as during the summer growing season. The factors affecting matric potential were amount and nature of precipitation, amount of run-in water, soil and vegetation type, position on the landscape, and microrelief.

Fire Effects on Tobosagrass and Weeping Lovegrass

Fireline intensity (kW/m) was measured on 61 plots of weeping lovegrass [Eragrostis curvula (Schrad.) Nees.] and tobosagrass [Hilaria mutica (Buckl.) Benth.] burned as headfires and backfires during late winters of 1982 and 1983 in western Texas. Relative humidity, air temperature, wind speed, soil moisture, soil temperature, and fuel moisture were measured at time of burning. Vegetation response was based on plant yield, plant height, and number of seed stalks. Plant responses were not correlated with fireline intensity or any of the environmental parameters measured. Although fireline intensity is an important fire behavior measurement, high fireline intensities did not cause a negative impact on either weeping lovegrass or tobosagrass. Therefore, range managers can conduct high intensity fires to damage or burn down shrubs and not damage these grasses.

Changes in Grass Basal Area and Forb Densities over a 64-Year Period on Grassland Types of the Jornada Experimental Range

Between 1915 and 1932, permanent 1 X 1-m quadrats were established on grasslands of the Jornada Experimental Range in southern New Mexico. Quadrat records accumulated from 1915 to 1979 on grasslands dominated by black grama [Bouteloua eriopoda (Torr.) Torr.], poverty threeawn (A ristida divaricata Willd.), tobosa [Hilaria mutica (Buckl.) Benth.], and burrograss (Scleropogon brevifolius Phil.) were used to examine changes in perennial grass basal area and forb densities. Quadrats originally dominated by black grama had large reductions in basal area during droughts, and basal area increased slowly following droughts. By 1979, black grama no longer occurred on 77% of the quadrats. Quadrats originally dominated by poverty threeawn changed to a mesquite (Prosopis glandulosa Torr. var. glandulosa) type. Perennial grass basal area on quadrats dominated by tobosa and burrograss decreased during droughts, but recovery was relatively rapid. Antecedent precipitation was associated with only 10 to 38% of the variation in perennial grass basal area. Perennial forb densities were low and fluctuated among years in all types. Annual forbs and grasses displayed large fluctuations in densities among years. The necessity of basing management of Chihuahuan Desert ranges on the perennial grass component is borne out by the low densities of palatable perennial forbs, and the extreme fluctuation and unpredictability in densities of annual forbs and grasses.

Microarthropods of a Desert Tabosa Grass (Hilaria mutica) Swale

We examined soil microarthropod populations inhabiting a clay-silt soil of a tabosa grass (Hilaria mutica) swale in southern New Mexico. Maximum population densities of soil microarthropods occurred in September (48,400.m-2) and lowest densities were in July (1,250-m 2). These densities were 50% lower than those reported for well-drained soils on the upper parts of the same watershed. Prostigmatid mites made up 67% and cryptostigmatid mites, 26%, of the total microarthropod population. The ratio between prostigmatid and cryptostigmatid mites, approximately 4:1, was consistent throughout the year. Overall densities of microarthropod groups were correlated with soil moisture but many individual taxa were not. The most numerous and frequently occurring taxa [nanorchestid, tydeid and bdellid mites (Prostigmata); Aphelacarus sp. and Cosmochthonius sp. (Cryptostigmata)] are common in all Chihuahuan desert habitats examined to date and are common in other North American desert areas. INTRODUCTION Microarthropods constitute a numerically important component of the soil fauna. Microarthropods play an active role in breakdown of dead plant parts (Santos and Whitford, 1981), in vertical transport of organic material through the soil profile, in humus formation, and they may also increase microbial activity by disseminating fungal spores (Wallwork, 1970). Santos et al. (1978) and Franco et al. (1979) found that, in two North American desert areas, the microarthropod fauna was dominated by prostigmatid mites rather than the oribatid mites that feed on dead plant material in more mesic environments. Loots and Ryke (1967) working in different South African biotopes found that the soil moisture content was not always the most important factor determining the composition of the soil rnicroarthropod fauna. They found a significant correlation between the ratio of oribatei/trombidiformes (= prostigmata) and the percentage of organic matter in different soils. Montane piedmonts, bajadas, in the desert Southwest of North America, drain onto clay basins or flats which form from the deposition of fine particles. The clay and swales are characterized by poor drainage and poor percolation. Following rains, they may be inundated for varying periods. Clay pans may be unvegetated or have sparse shrub and grass cover. Swales are characterized by a dense cover of tabosa grass, Hilaria mutica. Litter accumulation constitutes an important storage reservoir in desert ecosystems and may affect soil water, which is generally thought to affect the density of soil fauna. Because of the soil characteristics of swales, i.e., poor drainage, low infiltration and percolation, high soil water content and relatively high vegetative cover, we hypothesized that the soil fauna would differ in taxonomic composition and exhibit less seasonal change in population size than microarthropod populations in better-drained desert soils. We further hypothesized that the population densities would be higher and numbers of taxa would be lower than those found in erosional soils. Whitford et al. (1981) used simulated rainfall in comparison to natural rainfall to follow the responses of a number of taxa as the soils dried. They found marked shifts in 1Present address: Department of Biology, Bar-Ilan University, Ramat Gan, Israel. 2Address reprint requests to: W.G. Whitford, Department of Biology, New Mexico State University, Las Cruces 88003.

Response of Range Vegetation to Grid Placement and Aerial Application of Karbutilate

Karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxypheny)-1, 1-dimethylurea], formulated as a ball 1.34 cm in diameter, was applied to brush-infested rangeland with fixed-wing aircraft and in a grid pattern by hand at an average density of four balls/12.4 m2 (1.83-m spacing). Control of woody plants with karbutilate applied by hand in an exact grid pattern was not different from aerial applications at the same rate. Based on evaluations at least 24 months after application, karbutilate at 0.56 or 1.12 kg/ha did not control honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] in the subhumid Post Oak Savannah or semiarid Rolling Plains of Texas. At 2.24 kg/ha, canopy reduction of honey mesquite averaged 70% with 20 to 25% of the population killed. Post oak (Quercus stellata Wangenh.), blackjack oak (Quercus marilandica Muenchh.), yaupon (Ilex vomitoria Ait.), or winged elm (Ulmus alata Michx.) in Post Oak Savannah were not killed by 2.24 kg/ha. Karbutilate eliminated all vegetation in a 25 to 45-cm diameter circle, depending on concentration of active ingredient in the ball, the year of treatment regardless of vegetation region. The bare areas were revegetated within 2 yr following application in the Post Oak Savannah. However, bare areas in sodgrasses, primarily tobosa [Hilaria mutica (Buckl.) Benth.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.], where 1.12 and 2.24 kg/ha were applied averaged 20 to 30 in diameter, respectively, 32 months after application to sandy clay loam in the Rolling Plains.

Le partage des ressources alimentaires entre les espèces de lézards du désert de Mapimi, Mexique

The diet of several sympatric species of lizards has been studied in the Mapimi desert, Durango, Mexico, in order to elucidate the ways in which resource partitioning is achieved. Despite the optional specialization of the three Cnemidophorus species (termite eaters) and of Phrynosoma modestum (an ant eater), all these lizards are mostly opportunistic feeders ; their diets are highly diversified and largely overlapping. The larger lizards, which feed upon both large and small prey species, should exert a strong competitive pressure upon smaller lizards which are limited to smaller prey. However, small lizards avoid such a competition either by having a specialized diet (e.g. Phrynosoma modestum) or by living in certain microhabitats (e.g. Cnemidophorus inornatus which is confined to Hilaria mutica communities) . In such an ecosystem, resource partitioning among sympatric lizard species is therefore mostly achieved through microhabitat preferences, and also through different feeding strategies (e.g. the «sit-and-wait» technique versus the «widely foraging» technique).

Proper Burning Intervals for Tobosagrass in West Texas Based on Nitrogen Dynamics

Highlight: The time required for re-establishment of pre-fire nitrogen levels in tobosagrass (Hilaria mutica) communities in the Rolling Plains of West Texas was studied on five different ages of burns over a 2-year period. Time elapsed after burns varied from one to five growing seasons for both convex and concave topographic sites near Colorado City, Texas. Standing old growth-N returned to pre-fire levels by the end of the third growing season. However, litter-N on the soil surface took 5 years to reach pre-fire levels on concave sites and an estimated 8 years on convex sites. High variation prevented the recognition of any meaningful trends in root or soil nitrogen levels. Based on this data, tobosagrass should not be burned more frequently than 5 to 8 years, depending on the site.

Environmental Factors Influencing Semidesert Grassland Perennial Grass Demography

Long-term chart quadrat records from the Jornada Experimental Range in south-central New Mexico were photographed, the negatives analyzed with a flying-spot scanner, and the information converted for computer analyses. Some 35 quadrats with data from about 30 to 50 years duration were used giving records on the life-span of 12,437 perennial grass plants of seven species. Maximum life spans varied from 28 years for Bouteloua eripoda to only 7 years for Hilaria mutica. Mean life span for plants living at least 1 year varied from 3.8 to 3.0 years for these species. Average age-specific survival rates for seven perennial grasses increased from 0.39 at age 1 up to a maximum of 0.68 at age 7 and down to 0.48 at age 12. The level of grazing over the past years had little effect on plant survival, but cattle movement and trampling caused the death of some newly es- tablished grasses. A water-budget model produced results that could be readily interpreted in understanding plant survival. The relationship between the number of days of effective moisture in a given time period and the age-specific survival rates for each age class was pronounced. The period between the second and fourth age classes was most critical as regards availability of water. For newly established plants with shallow root systems, the precipitation of the immediate growing season was more important than precipitation for longer antecedent intervals. Continuous, reliable data, spanning long time periods are extremely rare for plant communities, particularly for herbaceous plants. Data on individual plants, necessary for examining many aspects of life history, are even more scarce. One of the major sources of such in- formation for herbaceous communities has been through chart quad- rat records in which permanently established quadrats are charted accurately over a period of years. Only limited amounts of such in- formation are reported in the literature. For humid and subhumid grasslands Harper (1960, 1967) has reported on demographic charac- teristics of Lemma minor and Salvina natans and Kerster (1968) reported on Liatris aspera. For semiarid and arid areas Nelson (1934)

Foodniche of Coyotes in the Rolling Plains of Texas

Highlight: Coyote diets were determined from scat and stomach analyses over a two-year period in an area centered in the Rolling Plains region of Texas. Fruit from 9 species of native plants were the most important food for coyotes, mainly as rainfall in May-and September. There is usually a dry making up 46% of the annual diet. Honey mesquite pods alone summer period with extremely high temperatures and contributed 15.6% of the annual diet. Rodents contributed evaporation, while the winters are relatively mild. The eleva24.5% of the coyote’s annual diet, while leporids made up just tion is approximately 550 m above sea level. Steep rocky hills 10.5%. The foodniche of coyotes varied seasonally as well as occur along the South Fork of the Wichita and Brazos Rivers annually. The coyote’s role as an agent of seed dispersal while flat to gently rolling topography occurs away from the appears minimal since digestion of some seeds by coyotes rivers. Honey mesquite (Prosopis glandulosa Torr. var. significantly reduces percent germination. Late evening and glandulosa), tobosagrass (Hilaria mutica), and buffalograss pre-dawn hours seem the normal feeding period for most (Buchloe dactyloides) are dominants on the deep hardland and coyotes, and moon phase did not affect the timing of this heavy clay range sites, while redberry juniper (Juniperus activity. In this study there was no evidence of coyote pinch0 tii), sideoats grama (Bou teloua curtipendula), and mesquite dominate in-the rough breaks. Pricklypear (Opuntia cow-calf operations on large ranches. Some ranchers also run stocker yearlings during the fall and winter. The average annual precipitation is 63 cm, which comes

Effects of Sodium Silicate Added to Rumen Cultures on Forage Digestion, with Interactions of Glucose, Urea and Minerals

Digestibility of organic matter in alfalfa hay, rangeland forages and purified cellulose (alpha-cellulose) was depressed by “soluble-silica” added to rumen cultures in the form of aqueous sodium silicate. In general, depression amounted to about one percentage unit of organic matter digestibility for each increase of 100 mg per liter (ppm) in “soluble silica” concentration for alfalfa hay, blue grama grass (cut green) and alpha-cellulose (plus glucose and urea); but the depression was greater when tobosa grass, a siliceous forage, was used as substrate. The effect of added silicate was modified by adding glucose, urea and/or a mixture of minerals (Mg, Mn, Zn, Co and Cu). The depression in digestibility due to silicate treatment involved mainly the degradation of fibrous materials in substrates rather than decreasing solubility of soluble organic matter. Availability of minerals to sustain cellulolytic microbial activity would appear to be a major factor influencing the effect of soluble silica on forage digestion by ruminants.

Fire in Medium Fuels of West Texas

Highlight: Chained and unchained mesquite in medium fuels were burned to measure the effect of prescribed burning on noxious brush species and on the production and utilization of major forage species. The fire did not kill any living mesquite trees. Very few standing dead mesquite stems burned down. Chained mesquite stems were easily consumed by fire with 2,000 lb/acre of fine fuel. Pricklypear and cholla mortality exceeded 50% by the end of the second growing season. Burning greatly increased production and utilization of tobosa grass; production of buffalograss was unaffected. Most annual forbs were harmed by burning.

The effect of humidity, air temperature, and wind speed on fine fuel moisture content

A controlled environmental chamber was used to study the effects of relative humidity, air temperature, and wind speed on moisture content of tobosa grass. Prediction equations were developed to show rates of change in fine fuel moisture content and equilibrium fine fuel moisture content for both absorption and desorption.

Pre-Emergence Herbicides for Seeding Range Grasses

CAMPBELL, R. S. 1931. Plant succession and grazing capacity on clay soils in southern New Mexico. J. Agr. Res. 43:1027-1051. CLEMENTS, F. E., AND V. E. SHELFORD. 1939. Bioecology. Wiley gc Sons Inc., N.Y. GONZALEZ, M. H. 1957. Grazing value and management of tobosa grass (Hilaria mutica (Buckl.) Benth.) on the Texas Range Station near Barnhart. M. S. Thesis, Texas A8cM Univ., College Station, Texas. 94 p. PAULSEN, H. A., AND F. N. ARES. 1962. Grazing values and management of black grama and tobosa grasslands and associated shrub ranges of the southwest. U.S. Dep. Agr. Tech. Bull. 1270, 56 p.

Effect of Spring Burning on Tobosa Grass

Effect of Spring Burning on Tobosa Grass

Effects of High Temperatures on Emergence and Initial Growth of Range Plants1

AbstractThe daily soil temperatures used in this light chamber study were patterned after observations made under field conditions: 18 to 39C where the surface was sparsely shaded by brush, and 18 to 53C where the surface was left bare. The soil moisture was maintained at field capacity. Emergence of sacaton (Sporobolus wrightii Munro), vine mesquite (Panicum obtusum HBK.), bush muhly (Muhlenbergia porteri Scribn.), and fourwing saltbush (Atriplex canescens (Pursh) Nutt.) was adversely affected by the high temperature regime. Survival of all 14 accessions except rhodesgrass (Chloris gayana Kunth), ‘Vaughn’ sideoats grama (Bouteloua curtipendula (Michx.) Torr.), and black grama (B. eriopoda (Torr.) Torr.) was reduced by the high temperature regime.At the close of the 21‐day trial most species had stopped growing or were growing very slowly under the high temperature regime. The shoot weights for the plants growing in the low temperature regime averaged nearly twice as much as those growing in the high temperature regime. There was no significant difference in root weight per seedling between temperature regimes. The root lengths of black grama, ‘Vaughn’ sideoats grama, tobosa (Hilaria mutica (Buckl.) Benth.), lehmann lovegrass (Eragrostis lehmanniana Nees), and alkali sacaton (Sporobolus airoides (Torr.) Torr.) were not reduced significantly by the high temperature regime.The high temperatures were detrimental, in one way or another, to all species even when moisture was adequate but black grama and sideoats grama performed satisfactorily.