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  Journal of Range Management, Volume 43, Number 2 (March 1990)

  Society for Range Management, 1990-03-01
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  Journal of Range Management, Volume 43, Number 3 (May 1990)

  Society for Range Management, 1990-05-01
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  Journal of Range Management, Volume 43, Number 4 (July 1990)

  Society for Range Management, 1990-07-01
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  Journal of Range Management, Volume 43, Number 5 (September 1990)

  Society for Range Management, 1990-09-01
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  Journal of Range Management, Volume 43, Number 6 (November 1990)

  Society for Range Management, 1990-11-01
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  Journal of Range Management, Volume 43, Number 1 (January 1990)

  Society for Range Management, 1990-01-01
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  Water relations of honey mesquite following severing of lateral roots: influence of location and amount of subsurface water

  Ansley, R. J.; Jacoby, P. W.; Cuomo, G. J. (Society for Range Management, 1990-09-01)

  Location and amount of subsurface water may ifiuenee the degree of dependence of honey mesquite (Prosopis glandulosa Torr.) on shallow lateral roots to supply water. The objective of this study was to determine influence of lateral roots on water relations of honey mesquite on 2 sites which differed in location and amount of subsurface water. Lateral roots were severed with barriers placed to 1.5 m depth and completely surrounding individual trees in February 1985, during mesquite winter dormancy. Stomatal conductance and predawn leaf water potential were signifiicantly reduced in root-severed trees during the following growing season (May-September) at both sites, but reduction was greater on the site with less subsurface water. Daytime leaf water potential was bigger in root-severed than control trees on tbe site with less subsurface water, but not on the other site. By mid-summer 1986, no difference in stomatal conductance between treatments were detected at either site, yet daytime leaf water potential remained higher in root-severed than control trees at the site with less subsurface water. Predawn leaf water potential was greater in root-severed than control trees in 1986, which was a reversal of 1985 trends. Leaf abscission was not observed in either treatment during either growing season. These results suggest that: (1) when less subsurface water was available, trees were more dependent on lateral roots to supply water, (2) treatment effects were minimized by the second growing season following root severing, possibly from new root growth within or below the root barrier region, and (3) the lateral root system may play a significant role in regulating leaf water relations on sites with limited subsurface water.
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  Warm-season grass establishment as affected by post-planting atrazine application

  Bahler, C. C.; Moser, L. E.; Griffin, T. S.; Vogel, K. P. (Society for Range Management, 1990-09-01)

  Atrazine [6-chloro-N-ethyl-N’-(l-methylethyl)-1,3,4-diamine] provides effective weed control during big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) establishment. However, most other desirable warm-season grasses are susceptible to atrazine injury at establishment. The objective of this study was to determine if atrazine application after seeding would affect susceptible warm-season grass establishment. Big bluestem, switchgrass, indiangrass [Sorghastrum nutans (L.) Nash] sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and little bluestem [Schizachyrium scoparium (Michx.) Nash] were seeded into greenhouse flats or field plots and 2.2 kg a.i. atrazine/ha applied at 0 (atrazine control), 7, 14, or 21 days after planting. An untreated control was used also. In greenhouse experiments, Indiangrass and sideoats grama plant survival increased when atrazine applications were delayed. Switchgrass, big blue stem, and little bluestem plant survival was not affected by atrazine application. Field studies were conducted in 1983, 1985, and 1986 using the same soil type, grass species, and application periods as the greenhouse study. Delaying atrazine application 7 or more days after planting generally favored survival of lndlangrass and sideoats grama. Big bluestem, switchgrass, and little bluestem were not affected by atrazine treatment. Delaying the application of atrazine may favor the survival of atrazine sensitive species. However, further research needs to be conducted on various soil types and environmental conditions before this can be a recommended practice.
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  Viewpoints: Range condition from an ecological perspective: Modifications to recognize multiple use objectives

  Pieper, R. D.; Beck, R. F. (Society for Range Management, 1990-11-01)

  Two changes in traditional range condition analyses are recom- mended: (1) to replace the terms excellent, good, fair, and poor with ecological equivalents of climax, late seral, mid-seral, and early seral in cases where this is practical; and (2) to develop relationships between products (e.g., livestock, wood products, water) or conditions (e.g., infiltration, site stability, erosion) and successional stage or state. Such information will allow the land manager to evaluate possible tradeoffs between managing for a particular successional stage or state and particular goods or services.
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  Vegetation response to time-controlled grazing on Mixed and Fescue Prairie

  Willms, W. D.; Smoliak, S.; Dormaar, J. F. (Society for Range Management, 1990-11-01)

  Improved carrying capacity of grasslands has been attributed to the effect of time-controlled grazing with high animal density, which can be achieved by increased stocking rates as well as by fencing. Therefore, a study was conducted to test the hypothesis that time-controlled grazing with high animal densities and high stocking rates will improve grassland condition. The study was made over a 6-year period on 3 sites with time-controlled grazing imposed. One site was on native grassland in the Fescue Prairie and 2 sites, 1 on seeded and the other on native grassland, were in the Mixed Prairie. On each site, stocking densities averaged 3, 6, and 15 cow-calf pairs/ha, respectively, and stocking rates averaged 1.65, 4.45, and 2.72 animal unit months/ha, respectively. Species composition and root mass and distribution were compared on grazed and protected areas within each site. Utilization averaged about 80% of available forage over the study period. Range condition was less on grazed areas than on protected areas in the Fescue Prairie (38 vs 53% of climax) and in the Mixed Prairie (49 vs 53%). Average ash-free root mass, throughout the sampling profile, tended to be greater on the ungrazed vs the grazed area of the native Mixed Prairie site but not on the seeded Mixed Prairie or Fescue Prairie sites. The grazed areas of the Mixed Prarie sites tended to have more available phosphorus, possibly due to the application of manure, but less nitrogen and organic matter. The results led to a rejection of the hypothesis and a conclusion that high animal density and high stocking rates with time-controlled grazing would result in range deterioration.
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  Vegetation response to increased stocking rates in short-duration grazing

  Ralphs, M. H.; Kothmann, M. M.; Taylor, C. A. (Society for Range Management, 1990-03-01)

  Short-duration grazing (SDG) has been purported to increase forage production and utilization compared to other grazing systems, and thus can sustain higher stocking rates. This study was designed to determine if standing crop could be maintained as stocking rates increased. Four stocking rate treatments ranging from the recommended rate for moderate continuous grazing to 2.5 times the recommended rate were applied in a simulated 8-pasture SDG system. There was little change in frequency and composition of short-grasses over the study, but mid-grass frequency and composition both declined. Standing crop of all major forage classes declined as stocking rates increased. However, the rate of decline was less than proportional to the increase in stocking rate during the growing season. By fall, standing crop was inversely proportional to stocking rate, leading us to conclude that standing crop could not be maintained at the higher stocking rates. Low standing crop in the fall indicated a potential shortage of forage at the high stocking rates during the winter.
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  Variability of crude protein in crested wheatgrass at defined stages of phenology

  Angell, R. F.; Miller, R. F.; Haferkamp, M. R. (Society for Range Management, 1990-05-01)

  Variability of crude protein concentration in crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult) is an important consideration in the development of grazing programs. Crude protein (CP) concentration in crested wheatgrass was monitored at specific stages of phenology for 5 years. During that time September through August precipitation varied from 68 to 142% of the 37-year mean. Vegetation was clipped once at 10 phenological stages beginning in April. At the last clipping date, in mid-August, regrowth accumulated after prior clippings was collected. Over the 5-year period, CP of vegetation clipped during mid vegetative growth in late April varied 35%, relatively, from 14.7% in 1983 to 9.5% during 1985. Even though 1984 crop year precipitation exceeded 1983 by 84 mm, maximum topgrowth biomass was 449 kg/ha lower in 1984. Also, CP percentage of vegetative growth in April was 1.8% lower in 1984 than in 1983. Regrowth CP was positively correlated (r=0.98) with June precipitation, and with the number of rain events in July (r=0.97). Plants clipped in the boot stage had greater forage CP in August than plants clipped prior to boot stage. However, regrowth biomass was affected by soil water availability and was highly variable. Crude protein in vegetative growth was marginal for growing steers in 1985. Although growing stock are often supplemented in late summer, these data are interpreted to show that spring supplementation may be needed some years.
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  Variability for seed size and yield in two tall dropseed populations

  Boe, A. (Society for Range Management, 1990-05-01)

  Tall dropseed [Sporobolus asper (Michx.) Kunth var. asper] is a drought-tolerant, perennial, warm-season grass that has potential for forage and soil conservation purposes. A prairie and an adjacent roadside population from northeastern South Dakota were evaluated for seed yield and size characteristics for 3 years (1985-1987) in a space-plant nursery at Brookings, S. Dak. The objective was to obtain information on between and within population variability and intraplant variability that would provide a basis for designing a breeding program to improve seed production and quality in this germplasm. The roadside population produced significantly (P<0.01) higher seed yields and larger mean 100-seed weight than the prairie population. Percent small seed (based on screen-separation of seed yields of individual plants into small, medium, and large seed size classes) decreased significantly (P<0.01) as seed yield increased, but the volume of small seed increased concurrently with seed yield. Percent large seed increased significantly (P<0.01) with increased seed yield and mean seed size. Highly significant (P<0.01) differences were found among years for seed yield and mean seed size, but all plants produced seeds of each size class each year. Inter- and intrapopulation genetic variability was indicated for yield of the large seed size class. Screen-separation of individual plant seed yields could be used to identify superior genotypes to be used in the development of a cultivrr that produces a high percentage of large seed.
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  Value of multiple fecal indices for predicting diet quality and intake of steers

  Leite, E. R.; Stuth, J. W. (Society for Range Management, 1990-03-01)

  The relationship of fecal nitrogen fractions and condensed tannins dietary crude protein, in vitro organic matter digestibility, and intake of steers was assessed to determine the suitability of these multiple fecal indices for predicting quality of animal diets under free-roaming conditions. Research was conducted on the Texas A&M Native Plant and Animal Conservancy near College Station, located in the Post Oak Savannah region of Texas. Regression equations were used to evaluate relationships between dietary intake and quality to fecal variables. Dietary crude protein, digestible organic matter, organic matter intake, crude protein intake, and digestible energy intake were determined from previous studies. Corresponding fecal samples were analyzed for absolute output, proportions, and concentrations of nitrogen and selected fractions of fecal organic matter, as well as fecal condensed tannins, proportions of fecal monocot and dicot fragments, and fecal organic matter. In general, no fecal parameter by itself had a high correlation with dietary variables when expressed on a proportion or concentration basis. A combination of fecal indexes accounted for more variation in dietary parameters than fecal nitrogen. Fecal nitrogen fractions did not improve the predictive power of multiple variable models. Equations predicting dietary crude protein (%) and crude protein intake yielded the highest coefficients of determination (R2 = .57 and .51, respectively). Multiple fecal indices used in this study were of limited value in predicting diet quality and intake.
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  Utilization of linear prediction procedures to evaluate animal response to grazing systems

  Winder, J. A.; Beck, R. F. (Society for Range Management, 1990-09-01)

  Best linear unbiased prediction (BLUP) procedures were used to separate genetic merit from environmental effects on 205-d weight (205-d wt) of calves produced by cows grazing 2 pasture systems. Phenotypic measures of 205-d wt were statistically partitioned into genetic effects (breeding value) and environmental effects. Means were regressed on year of birth of calf. Analysis of covariance was used to test difference in slope and elevation (means) of the regression lines. The continuously grazed pasture (CC) produced higher 205-d wt than did the rotationally grazed pastures (RG) (P<.10). Rate of change in 205-d wt was similar in the 2 grazing systems. Genetic merit was similar among the animals in the 2 grazing systems. The rate of change per year in genetic merit (genetic trend) was also similar. Means tended to vary sharply from year to year, indicating inequality of genetic merit should be taken into account in this type of data. Mean environmental effects resulted in greater (P<.10) 205-d weight in CG than in RG. Rate of change of environmental quality was similar in the 2 systems. These results indicate, from the animals perspective, the RG system did not improve productivity when compared to CG. The CG system was of higher nutritional quality, but the rate of change was similar to that of the RG system.
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  Using multivariate techniques to quantitatively estimate ecological stages in a mixed grass prairie

  Uresk, D. W. (Society for Range Management, 1990-07-01)

  Cluster analysis followed by stepwise discriminant analysis was used to delineate ecological stages on a mixed grass prairie in western South Dakota. Forty-seven variables were analyzed for 48 sites ranging from potential vegetatlon to early seral stages. A cover-frequency index for western wheatgrass (Agropyron smithii), blue grama (Bouteloua gracilis), and buffalograss (Buchloe dactyloides) was the most valuable in identifying 4 different (P<0.0001) ecological stages. Ecological stage classification was estimated to be 95% accurate. The methods presented are quantitative, precise, easy, time-efficient, and meet the goals of resource managers with a minimum of bias.
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  Trampling effects from short-duration grazing on tobosa-grass range

  Weigel, J. R.; Britton, C. M.; McPherson, G. R. (Society for Range Management, 1990-03-01)

  Emergence of broadcast-seeded kleingrass (Panicum coloratum L. 'Selection 75') was compared for 2 seasons in short-duration grazed (SDG) areas and ungrazed exclosures in the Texas Rolling Plains in order to test the hypothesis that short duration grazing (SDG) increases seedling emergence. Kleingrass emergence was similar between treatments in both years. Emergence was unrelated to percent foliar cover of preexisting vegetation. Soil strength was greater in grazed areas in both years, but showed evidence of recovery between years. Trampling under short-duration grazing provided no beneficial effect on kleingrass emergence or soil strength in either year.
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  Timahdit sheep production and behavior at three stocking rates in the Moyen Atlas of Morocco

  El Aich, A.; Rittenhouse, L. R.; El Khamkhami, S.; Mhand, T. A. (Society for Range Management, 1990-09-01)

  Liveweight (LW) changes and behavior of growing rams were measured in 1981, 1982, 1985, and 1986 at the Timahdit Experiment Station in the Middle Atlas, Morocco, at stocking rates of 2.78, 4.17, and 6.67 rams/ha during the growing season. Maximum animal production would have occurred at a stocking rate greater than any imposed in the study in all years except 1982. Increased variable costs should drive stocking rates down while increased selling price would provide an incentive to increase stocking rates. Mean grazing time of animals stocked at tight, moderate, and heavy rates was 410, 436, and 504 minutes/day, respectively. Mean resting time was 206, 174, and 106 minutes/day, respectively. Rams under light, moderate, and heavy stocking rates walked 2.1, 2.4, and 3.1 km/day, respectively. Diet IVDMD was highest early in the grazing season and lowest in the nongrowing season, and was not affected by stocking rates. Early in the spring, diet diversity was low, increased during active growth, and then deciined as the season advanced. Selectivity was lowest when forage was abundant. Dry matter intake varied with season in 1985 but not 1986. There was less opportmdty to be adaptive under heavy than under light stocking, resulting in a stocking rate by season interaction in 1986. Under heavy stocking, forage intake (G/kg LW/min) was 61 and 83% of intake under light and moderate stocking, respectively, and forage intake per km walked was 71 and 84%, respectively
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  Tiller defoliation patterns under short duration grazing in tallgrass prairie

  Gillen, R. L.; McCollum, F. T.; Brummer, J. E. (Society for Range Management, 1990-03-01)

  Simulated 8-pasture short duration grazing systems were studied in 1985-86 to determine the effect of grazing schedule and stocking rate on defoliation patterns of individual grass tillers of big bluestem (Andropogon gerardii Vitman) and little bluestem (Schizachyrium scoparium (Michx.) Nash). Treatments consisted of 3 grazing schedules (2, 3, or 4 rotation cycles per 152-day grazing season) and 2 stocking rates (1.3 and 1.8 times the recommended normal). Grazing schedule and stocking rate did not affect the percent tiller height reduction per grazing period except for the combination of 2-cycle grazing and heavy stocking which increased percent height reduction. Percent tiller height reduction per grazing period decreased over the grazing season for the 3 and 4-cycle grazing schedules. Grazing schedule and stocking rate had little effect on the height at which tillers were defoliated. Increasing the number of grazing periods reduced the percentage of tillers defoliated per grazing period but increased the cumulative defoliation frequency over the grazing season. Grazing schedule did not affect the percentage of tillers ungrazed over the entire grazing season. Big bluestem was consistently defoliated more intensely and frequently than little bluestem.
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  The effect of water stress on phenological and ecophysiological characteristics of cheatgrass and Sandberg's bluegrass

  Link, S. O.; Gee, G. W.; Downs, J. L. (Society for Range Management, 1990-11-01)

  Comparative field studies of cheatgrass (Bromus tectorum L.) with Sandberg’s bluegrass (Poa sandbergii Vasey) were conducted to further our understanding of the plant characteristics that contribute to success in habitats where water is a limiting factor. To evaluate the effect of soil water on phenological development, stomata1 conductance, and xylem pressure potential of these grasses, observations were made in the field for 2 growing seasons (1986 and 1987). Stomata1 conductance, transpiration, and xylem pressure potential data, gathered as soils dried during 1986, indicated that water stress developed earlier and to a greater degree in Sandberg’s bluegrass than in cheatgrass. Xylem pressure potential was lower in Sandberg’s bluegrass than in cheatgrass, and the difference increased throughout the growing season. Stomata1 conductance and transpiration were greater for cheatgrass than for Sandberg’s bluegrass. Maintenance of high soil water potentials by irrigating through the 1987 growing season retarded phenological development and delayed senescence by about 10 days for both species. Predawn xylem pressure potential for irrigated plants remained higher than for nonirrigated plants; however, as the plants senesced, xylem pressure potential also decreased in the nonstressed plants.

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