• An Evaluation of Grazing Intensity Influences on California Annual Range

      Rosiere, R. E. (Society for Range Management, 1987-03-01)
      Influences of grazing intensity on species composition and herbage production of grass-woodland and improved grassland subtypes of annual range were evaluated over a 5-year period in coastal northern California using 3 grazing treatments (100, 150, and 200% of moderate stocking). Herbage utilization did not differ significantly between the 2 subtypes but averaged 42, 52, and 69% for the respective treatments. Plant species and production responses differed significantly between woodland and grassland subtypes. On woodland, ripgut brome (Bromus rigidus Roth.) and wild oats (Avena barbata Brot. and A. fatua L.) were most sensitive to grazing intensity while wild barley (Hordeum leporinum Link. and H. hystrix Roth.) and annual fescue (Festuca dertonensis (all.) Asch. and Graebn. and F. megalura Nutt.) were least sensitive. On improved grassland, subterranean clover (Trifolium subterraneum L.) increased and soft chess (Bromus mollis L.) decreased with increasing grazing intensity. Soft chess remained most plentiful on woodland range under heaviest grazing and it continued to be a major species under heavy grazing of grassland, demonstrating tolerance to grazing intensity. Filaree (Erodium cicutarium (L.) L'Her. and E. botrys (Cav.) Bertol.) declined on woodland but increased on grassland as grazing intensified. Peak standing crop was not significantly affected by grazing intensity on woodland range but was greatest at 150% of moderate stocking and lowest at 200% of moderate stocking on grassland range. Decline in grassland herbage yield under heaviest grazing was due to reduction of soft chess which was displaced by subterranean clover. Effects of grazing intensity on range composition and productivity were confounded by innate differences in ranges and yearly weather patterns. Herbage production was impacted more by annual growing conditions than by grazing regimens, but there was no correlation between total annual precipitation and peak standing crop.
    • Germination Response of Three Globemallow Species to Chemical Treatment

      Roth, T. E.; Holechek, J. L.; Hussain, M. Y. (Society for Range Management, 1987-03-01)
      Scarlet (Sphaeralcea coccinea), orange (Sphaeralcea munroana), and gooseberry globemallow (Sphaeralcea grossulariaefolia) seed were soaked in 18 m sulfuric acid; 1 m, 1,4-dioxane; and sulfuric acid plus dioxane to increase germination. A 3 to 4-hour soak in dioxane significantly (P<.05) improved germination of all species over the control, and was the best treatment when data were pooled across species. Scarlet globemallow had the highest germination when subjected to 10-minute soak in sulfuric acid. Dioxane is a highly flammable, potentially cancer inducing chemical not readily available to most personnel interested in seeding globemallow. In contrast, sulfuric acid is a readily available chemical that poses a relatively minimal hazard to human health if handled correctly. A 10-minute soak in sulfuric acid appears to be a very practical treatment for improving the germination of scarlet and gooseberry globemallow. However, orange globemallow germination (P>.05) was not improved by sulfuric acid treatment.
    • Examination of Methods for Estimating Rate of Passage in Grazing Steers

      Cochran, R. C.; Adams, D. C.; Galyean, M. L.; Wallace, J. D. (Society for Range Management, 1987-03-01)
      Understanding how rate of passage estimates are influenced by procedural variations may facilitate standardization of methodology and enhance comparisons among studies. Therefore, 12 ruminal-fistulated beef steers (mean wt. = 294 kg) were used in two 6-day grazing trials to evaluate influences of sampling site, intraruminal mixing, and mathematical model on particle passage rate estimates. Steers grazed a 13-ha pasture of immature crested wheatgrass. We estimated particle passage rate from the rumen by intraruminal administration of a pulse dose of Yb-labeled forage followed by serial collection of ruminal digesta or fecal samples. Treatments were (1) rectal sampling; (2) ruminal sampling-ruminal contents mixed before subsampling digesta; (3) ruminal sampling-ruminal contents not mixed before subsampling digesta. All steers were fitted with vibracorders to monitor grazing time before and during sampling periods. Fecal Yb curves were fitted with a one compartment, time-dependent (ICMPT-TD), a two-compartment, sequential time-dependent-time-independent (2CMPT-TD), and a two-compartment, time-independent (2CMPT-TI) model. All ruminal Yb curves were fitted with a single exponential decay model. Comparisons among models were limited to rate constants associated with the slower escape process. Intraruminal mixing did not alter (P>0.10) passage rates. The 2CMPT-TD model failed to fit some fecal profiles. Particle passage rates from the 2CMPT-TI model were greater (P<0.05) than those from the ICMPT-TD model. Similarity among passage rate constants derived from fecal Yb curves and those derived by semilogarithmic regression of ruminal Yb concentration on time depended on the model used to fit fecal Yb curves. Grazing time decreased (P<0.01) during intensive sampling periods. We conclude that for steers grazing immature grass pastures, intraruminal mixing before subsampling does not significantly alter rate of passage estimates; however, site of sampling and mathematical model may be important factors to consider in choosing appropriate methodology for estimating rate of passage.
    • Carbohydrates in Leafy Spurge Roots as Influenced by Environment

      Lym, R. G.; Messersmith, C. G. (Society for Range Management, 1987-03-01)
      The total nonstructural carbohydrate (TNC) content of leafy spurge (Euphorbia esula L.) roots was determined for 4 consecutive growing seasons. The variations in water soluble (monosac-charide and disaccharide) and water insoluble or reserve carbohydrate content were compared to selected environmental parameters. TNC concentration reached maximum levels of 300 mg/g in mid-summer and early fall, but declined rapidly to 190 mg/g or less late in the growing season. The soluble carbohydrates, mostly sucrose, increased as the plant cold-hardened, while the insoluble carbohydrate content declined to near zero. Abrupt changes of root carbohydrate content could not be explained solely by the growth pattern of leafy spurge. Soluble carbohydrate content was high during periods favorable for growth, but insoluble reserves increased during periods of environmental stress. Root soluble carbohydrate content varied inversely with changes in the six day mean air temperature with an average partial correlation coefficient of -0.75. Soluble carbohydrate content increased as the mean temperature decreased and declined as the mean temperature increased, but was independent of a specific temperature. The insoluble carbohydrate content was positively correlated with temperature. Root carbohydrate content also varied with fluctuations in the maximum and minimum temperature, dew point, and total pan evaporation, but not with precipitation.
    • Frequency Sampling in Microhistological Studies: An Alternative Model

      Williams, B. K. (Society for Range Management, 1987-03-01)
      Frequency sampling in microhistological studies is discussed in terms of sampling procedures, statistical properties, and biological inferences. Two sampling approaches are described and contrasted, and some standard methods for improving the stability of density estimators are discussed. Possible sources of difficulty are highlighted in terms of sampling design and statistical analysis. An alternative model is proposed that accounts for 2-stage sampling, and yields reasonable, well-behaved estimates of relative densities.
    • Effects of Temperature, Light, and Scarification on Germination of Brownseed Paspalum Seeds

      Flenniken, K. S.; Fulbright, T. E. (Society for Range Management, 1987-03-01)
      Brownseed paspalum (Paspalum plicatulum Michx.) is an important forage grass in tropical and subtropical regions. This study investigated effects of temperature, light, and scarification on germination of seeds from Texas, Australia, South America, and Africa. Seed sources included PI-353399 (Ivory Coast), 'Bryan' (Australia), Paspalum plicatulum 600 (Columbia), and collections from De Witt and Hidalgo Counties, Texas. Untreated seeds and seeds scarified in 17 M sulfuric acid for 20 minutes were germinated under light (12 hours daily) and dark conditions at alternating temperatures of 5-15 (12 hours-12 hours), 10-20, 15-25, 20-30, 25-35, and 30-40 degrees C for 28 days. Seeds from all sources showed similar responses to temperature for percent germination and corrected germination rate index (CGRI). Highest percent germination of Hildalgo seeds occurred at 20-30 and 25-35 degrees C, while that of other sources occurred at 25-35 and 30-40 degrees C. Maximum CGRI for most sources was at 30-40 degrees C. Percent germination was generally higher in light than dark. Scarification increased percent germination and CGRI of De Witt, Hidalgo, PI-353399, and Bryan seeds. Our data indicate that brownseed paspalum seeds are adapted for warm-season germination.
    • Effects of Hay and Straw Mulches on the Establishment of Seeded Grasses and Legumes on Rangeland and a Coal Strip Mine

      McGinnies, W. J. (Society for Range Management, 1987-03-01)
      Straw and grass-hay mulches at rates of 1,120 and 3,360 kg/ha were applied to the surface after seeding or incorporated into the soil before seeding for 3 consecutive years of planting at Central Plains Experimental Range (CPER) near Nunn, Colorado, and at Colorado Yampa Coal Company mine (CYCC) near Steamboat Springs, Colorado. Averaged across 3 years, the stand ratings of Psathyrostachys juncea (Fisch.) Neveski, the only species seeded at CPER, were significantly better for the check (no mulch) treatment than for any mulch treatment. At CYCC, average stand ratings were significantly better than the check when 1,120 kg/ha of straw mulch was applied to the surface after seeding. The species that consistently had the best stand ratings at CYCC were Astragalus cicer L., Bromus biebersteinii Roem and Schult., B. inermis Leyss., B. marginatus Nees, Elytrigia intermedia (Host) Nevski, E. intermedia subsp. barbulato (Schur) A. Löve, Medicago falcata L., M. sativa L., and Phleum pratense L. No erosion from the plots by either wind or water was observed regardless of mulch treatments.
    • Growth and Reproduction of Grasses Heavily Grazed Under Rest-Rotation Management

      Eckert, R. E.; Spencer, J. S. (Society for Range Management, 1987-03-01)
      This study evaluated the effects of heavy forage use in a rest-rotation grazing system on the basal-area growth and frequency of occurrence of native bunchgrasses from 1975 to 1984. None of these grasses increased in basal-area cover with brush competition or in basal-area cover or frequency without brush competition when subjected to periodic heavy grazing (65% utilization in June and 75% in July) during the growing season. When plants were protected from grazing, average basal-area cover increased for Idaho fescue [Festuca idahoensis Elmer] and squirreltail [Sitanion hystrix (Nutt.) J.G. Sm.] in a Wyoming big sagebrush [Artemisia tridentata wyomingensis Beetle]-Idaho fescue community type and for Thurber needlegrass [Stipa thurberiana Piper] in a Wyoming big sagebrush-bluebunch wheatgrass [Agropyron spicatum (Pursh) Scribn. & Smith] community type. Average basal-area cover was unchanged for protected Thurber needlegrass plants in a Wyoming big sagebrush-Thurber needlegrass community type. Average basal-area cover of Thurber needlegrass plants in the same community type decreased when heavily grazed during the growing season in 1 year during the first 3 years of the study and with no grazing during the growing season in the last 4 years of the study. Bluebunch wheatgrass showed no differential response to grazing or protection. Results of this study strongly implicate periodic heavy grazing during the growing season as a primary cause of restricted basal-area growth and lack of reproduction. These results support the contention that such grazing pressure can prevent range improvement in an otherwise appropriate rotation grazing system.
    • Growth of Introduced Temperate Legumes in the Edwards Plateau and South Texas Plains

      Holt, E. C.; Haferkamp, M. R. (Society for Range Management, 1987-03-01)
      A study was conducted to evaluate production of 2 temperate, annual legumes at locations where temperature and moisture may seasonally place severe constraints on growth. Arrowleaf (Trifolium vesiculosum Savi) and subterranean (Trifolium subterraneum L.) clovers were grown at Beeville, in south Texas, and at Brady, 230 miles north of Beeville. Standing crop samples were collected at approximately 2-week intervals, starting 30 days post emergence and continuing to plant maturity during 2 years. Very little growth was made prior to 1 March at Brady in either year or at Beeville the first year. Total production was minimal (<1,500 kg/ha) at Brady. Arrowleaf produced about twice as much standing crop as subterranean at Beeville, 3,900 to 8,800 kg/ha (arrowleaf) versus 2,800 to 4,600 kg/ha (subterranean). No environmental variable showed a close association with growth rate when the data for 2 years and 2 species were included in simple correlations. In stepwise multiple regression equations, daily heat units was the most important variable followed by soil water. Early fall emergence and the development of a supraminimal canopy prior to the advent of growth-limiting winter temperatures had an overriding effect on winter growth as indicated by production differences in the 2 years at Beeville. The study shows that temperate annual clovers can be grown further west in the Southern region than current usage indicates.
    • Subterranean Clover on Southern Pine Range: Potential Benefits to Game

      Ribbeck, K. F.; Johnson, M. K.; Dancak, K. (Society for Range Management, 1987-03-01)
      Wildlife habitat is an important component of forested lands in the South. We examined effects of silvicultural practices and understory management on abundance of arthropods for wild turkey (Meleagris gallopavo) and bobwhite (Colinus virginianus). Plots (roughtly equal to 0.1 ha) of southern pine timber (25-35 years old) were thinned or cleared and were planted with subterranean clover (Trifolium subterraneum) or were allowed to produce native vegetation. Arthropods were most abundant in clearings for both understory treatments: 127 +/- 15 (subterranean clover), 45 +/- 5 (native) per plot. Abundance of arthropods on pine forested plots with a subterranean clover understory was often greater than abundance of arthropods on cleared plots with native vegetation. Many of the arthropods sampled were the kinds often used by wild turkey and bobwhite. Subterranean clover production on forested plots was about 70% of production on cleared plots. Arthropods from 5 of 8 orders were significantly (P<0.05) more abundant in subterranean clover plots compared to native vegetation. Abundance of arthropods was significantly (P<0.05) associated with forage yield. Dead subterranean clover provided more arthropods in summer than live native vegetation. Planting subterranean clover in Southern pine timber offers a good alternative to removal of timber production for improving wildlife habitat and for integrating livestock and game management practices. Costs for establishing (roughly equal to $100/ha) and maintaining (roughly equal to $50/ha/yr) subterranean clover under pine timber are less than the potential loss in timber revenue ($125 to 340/ha/yr) associated with maintaining clearings.
    • Temperature and Scarification Effects on Germination of Prostrate Bundleflower Seeds

      Fulbright, T. E.; Flenniken, K. S. (Society for Range Management, 1987-03-01)
      A hard seed coat restricts germination of prostrate bundleflower [Desmanthus virgatus var. depressus (Humbolt and Bonpland ex Willd.) Turner] seeds. Our objectives were to determine: (1) the effects of temperature on germination of scarified and untreated seeds in the light and dark and (2) the efficacy of various presowing treatments in increasing germination. Scarified (nicked with a razor blade) and untreated seeds were germinated at 5-15, 10-20, 15-25, 20-30, 25-35, and 30-40 degrees C (12 hours - 12 hours) in the dark or with light during the warmer temperature. Effects of scarification with 17 M H2 SO4, hot (80 degrees C) water, 0.7 mol liter-1 NaOCl, 2.9 mol liter-1 H2O2, and nicking with a razor blade on germination were compared. Maximum germination of untreated seeds was only 6%. Germination of scarified seeds exceeded 90% at 15-25 degrees C and higher temperatures. Light did not affect germination at optimal temperatures for germination. Nicking seeds with a razor blade, soaking 40 minutes in 17 M H2 SO4, and soaking 25 minutes in hot (80 degrees C) water resulted in 91, 88, and 78% germination, respectively, compared to 3% for controls. Our results indicated that, for best germination, seeds should be soaked 40 minutes in 17 M H2 SO4 or nicked with a razor and planted when mean minimum-maximum soil temperatures exceed 15-25 degrees C.
    • Passage Rates, Rumen Fermentation, and Weight Change in Protein Supplemented Grazing Cattle

      Judkins, M. B.; Wallace, J. D.; Galyean, M. L.; Krysl, L. J.; Parker, E. E. (Society for Range Management, 1987-03-01)
      Protein supplementation is widely used to enhance the nutritional status of cattle on rangeland. The effects of protein supplementation on particulate and fluid passage rates, rumen fermentation, and weight gain were evaluated on cattle grazing dormant blue grama rangeland. Twelve rumen-cannulated steers were randomly allotted to 3 equal supplement groups (4/treatment): cottonseed cake (CSC), pelleted alfalfa (ALF), or no supplement (CON). Supplements were individually fed every other day at isonitrogenous levels (1.7 kg/hd CSC vs 3.6 kg/hd ALF). Particulate passage rate was measured during 2 collection periods. Concurrently, 102 yearling heifers were allotted to the same treatment groups for measurement of average daily gain. Cattle were fed these treatments from January through April 1983. In a second trial, 9 rumen-cannulated steers were randomly allotted to the same treatment groups as trial 1. An intraruminal dose of Co-EDTA was used to estimate fluid passage rates. Rumen ammonia, volatile fatty acids, and pH were also measured. In trial 1, average daily gain did not differ between ALF and CSC supplemented heifers; however, both ALF and CSC gained more than CON heifers. Passage rate estimates were not different among treatment groups. In trial 2, rumen fluid dilution rate, volume, and outflow rate were not different among treatments. Rumen ammonia-N was different at 11 h postsupplementation when the CSC steers had higher levels than steers in other treatment groups. Rumen pH was not influenced by supplementation. Molar proportions of acetate and propionate at 8 and 11 h after supplementation differed among treatment groups. Acetate was lowest in ALF, intermediate in CSC, and highest in CON supplemented steers. Propionate followed the reverse trend. Overall, protein supplementation improved livestock performance but the mechanism involved was not elicited. The current data suggest shifts in fermentation patterns and meeting dietary demands for gain are the factors involved in improving performance.
    • Procedure for Fecal Cuticle Analysis of Herbivore Diets

      Stevens, E. J.; Stevens, S. J.; Gates, R. N.; Eskridge, K. M.; Waller, S. S. (Society for Range Management, 1987-03-01)
      Cuticular imprints of underlying plant tissue which survive ruminant digestion in herbivore feces provide a reliable taxonomic basis for species identification provided they can be adequately prepared for microhistological analysis. Objectives of this research were to investigate the discernibility of alfalfa (Medicago sativa L.) cuticle in sheep feces and document a procedure for fecal cuticle analysis. A completely random design with 4 replications was used with a split-plot arrangement of treatments. Diet treatments were applied to whole-plots and fecal preparation techniques were applied to subplots. Mature wethers were fed diets containing 25, 50, or 75% prebloom alfalfa hay with vegetative indiangrass [Sorghastrum nutans (L.) Nash] hay. A fecal cuticle procedure was described which established a linear relationship between dietary and fecal alfalfa contents. Under conditions where species characterized by fragile cuticle (such as alfalfa) are part of the dietary intake and diet is low in woody species, cuticle procedures may represent an alternative method for dietary composition analysis. An epidermal preparatory technique used in conjunction with fecal cuticle procedures did not establish a linear relationship between dietary and fecal alfalfa contents.
    • Revegetation of Oil Well Reserve Pits in West Texas

      McFarland, M. L.; Ueckert, D. N.; Hartmann, S. (Society for Range Management, 1987-03-01)
      On-site disposal of drilling fluids frequently causes severe, longterm disturbance of rangeland soils. The effects of mulch on establishment and standing crops of seeded kochia [Kochia scoparia (L.) Schrad.], King Ranch bluestem [Bothriochloa ischaemum (L.) Keng], Lehmann lovegrass (Eragrostis lehmanniana Nees), kleingrass 'Selection 75' (Panicum coloratum L.), alkali sacaton [Sporobolus airoides (Torr.) Torr.], and fourwing saltbush [Atriplex canescens (Pursh) Nutt], and transplanted fourwing saltbush were evaluated on 4, recently covered oil well reserve pits in Reagan County Texas, in 1981 and 1982. On-site disposal of drilling fluids resulted in substantial to large increases in sodium adsorption ratios (SAR) and concentrations of soluble salts, primarily sodium chloride, in reserve pit soils. Mulching with 4,500 kg/ha of weathered hay had no effect, but irrigation was essential for establishment and growth of the seeded species on severely contaminated soils (ECe 71 to 114 dS m-1, SAR 33 to 127). Mulching improved establishment and yields of seeded King Ranch bluestem and kleingrass on reserve pit soils with ECe values of 9 to 11 dS m-1 and SAR values of 12 to 16. Application of 5.1 cm of supplemental water and mulching reserve pit soils with Ece values of 3 to 7 and SAR values of 5 to 9 stimulated establishment of competing vegetation, which tended to decrease establishment and yields of seeded and transplanted species. Establishment and yields of transplanted fourwing saltbush were acceptable with or without mulching or irrigation. Survival of fourwing saltbush transplants was near 100% on moderately contaminated soils and 26 to 30% on severely contaminated soils.
    • Technical Notes: Survival Analysis of Single and Twin Lambs

      Scrivner, J. H.; Dally, M. R.; Howard, W. E. (Society for Range Management, 1987-03-01)
      We illustrate the use of life tables and survival analysis for evaluating data on livestock losses. The techniques are used to compare the rate of coyote (Canis latrans) predation on single and twin lambs. Based on the number of lambs known to have been killed by predators, the survivorship of single and twin lambs was not significantly different (P>0.05) for any year of the study. Survival functions which can be generated and used to evaluate data on livestock losses include the cumulative proportion of livestock surviving at the end of an interval, probability density, and hazard rate.
    • Understory Herbage Production of Major Soils within the Black Hills of South Dakota

      Bennett, D. L.; Lemme, G. D.; Evenson, P. D. (Society for Range Management, 1987-03-01)
      Two-year understory production was determined on 6 major forest soils across 2 geomorphic regions in the Black Hills of South Dakota. Stepwise multiple regression was used to determine those variables best explaining yield variability. Canopy cover, basal area, soils, May-June precipitation, and soil × cover interactions further improved the models, which accounted for 65 to 76% of the variability in herbage production. Footslope, nonskeletal soils had the highest herbage production (yielding 1,800 kg/ha at 0% canopy cover). The least developed, backslope, skeletal soil had the lowest herbage production (producing only 550 kg/ha at 0% canopy cover) from comparable areas of the Black Hills. Developed models can be used in conjunction with soil survey reports to estimate the forage potential of a given soil mapping unit. Results from this study emphasize the importance of considering the understory vegetation production potential of individual soil series when developing grazable woodland management plans. Soil-related production differences were most strongly expressed under conditions of limited overstory canopy cover.
    • Using Leaf Fluorescence for Evaluating Atrazine Tolerance of Three Perennial Warm-Season Grasses

      Bahler, C. C.; Moser, L. E.; Vogel, K. P. (Society for Range Management, 1987-03-01)
      Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] blocks photosynthetic electron transport in susceptible plants. The energy from the interrupted electron transport is fluoresced from the leaves of atrazine-treated plants. The purpose of this study was to evaluate leaf fluorescence as a nondestructive bioassay of the relative atrazine tolerance of 3 perennial, warm-season grasses. Leaf section of switchgrass [Panicum virgatum L.] (high tolerance), indiangrass [Sorghastrum nutans (L.) Nash] (intermediate tolerance), and sideoats grama [Bouteloua curtipendula (Michx.) Torr.] (lower tolerance) were placed in distilled water for 20 min and then in atrazine solutions. Fluorescence readings were taken prior to and after the atrazine treatment with a portable fluorometer. The difference between the 2 readings provided a reliable measure with low variability of the relative atrazine tolerance of the grasses studied and was effective on greenhouse-and field-grown plants. Optimum atrazine concentrations and incubation periods were 10^-3 M (atrazine in distilled H2O and 30 min, respectively.
    • Variation in Utilization of Big Sagebrush Accessions by Wintering Sheep

      Welch, B. L.; McArthur, E. D.; Rodriguez, R. L. (Society for Range Management, 1987-03-01)
      We observed the effects of accessions of big sagebrush (Artemisia tridentata) on big sagebrush utilization by wintering domestic sheep. The sheep had continuous access to high quality alfalfa hay and were fed 0.28 kg of rolled barley per head per day. Utilization was expressed as a percent of the current year's vegetative growth consumed by the sheep and also as grams of dry matter eaten per stem. Utilization of accessions varied from 0 to 98% over 3 sites and from 0 to 7.112 g of dry matter per stem. The sheep tended to remove significant (60 to 70%) amounts of current growth from the more preferred accessions before removing even small (15%) amounts of less preferred accessions. If this is typical grazing behavior, preferred big sagebrush plants may be lost in areas subject to repeated grazing.
    • Variations in Physiological Metabolites and Chlorophyll in Sexual Phenotypes of 'Rincon' Fourwing Saltbush

      Tiedemann, A. R.; McArthur, E. D.; Freeman, D. C. (Society for Range Management, 1987-03-01)
      An experiment was conducted to determine if concentrations of chlorophyll and basic metabolites (total organic nitrogen (TN), total phosphorus (TP), and total nonstructural carbohydrates (TNC)) were an indication of the physiological vigor of the 3 sexual phenotypes of fourwing saltbush (Atriplex canescens (Pursh) Nutt.). Our basic hypothesis was that males, females, and plants capable of male and female sex expression (sexually labile) were equally vigorous as was manifested in chlorophyll and metabolite levels. In June, concentrations of chlorophyll a, b, and total chlorophyll in the male phenotype were greater than in either the female or the labile phenotypes. There were no differences among phenotypes for the other dates. Male plants had the highest levels of metabolites (TN, TP, and TNC) when any differences among sexual phenotypes were significant. There were basically no differences in metabolite concentration between the female and labile sexual phenotypes. Results indicate that part of the hypothesis should be rejected-that male, female, and sexually labile plants are equally vigorous based on concentrations of chlorophyll and metabolites. Part of the hypothesis, however, can be accepted-that females and labile plants are comparable in physiological vigor. Levels of all 3 metabolites showed striking trends among sample dates, which indicated that fourwing saltbush has the capability of rebuilding its levels of metabolites in the spring at the physiologically costly time of flowering. This may be related to the photosynthetic efficiency associated with its C-4 photosynthetic pathway.