• Viewpoint: A view on species additions and deletions and the balance of nature

      Johnson, H. B.; Mayeux, H. S. (Society for Range Management, 1992-07-01)
      Popular assumptions about ecosystem stability and the delicate balance of nature are found lacking when examined in terms of paleoecological, historical and current biochronological, and biogeographical sequences in a wide variety of environments. Species composition of vegetation varies continuously in time as well as space in the absence of acute perturbations. Species have been added to or removed from ecosystems without greatly affecting ecosystem function. Natural ecosystems exhibit greater stability (inertia) in physiognomic structure and functional processes than in species composition. For instance, creosotebush became dominant over many millions of hectares of the Chihuahuan, Sonoran, and Mojave Deserts over a short period of 11,000 years, but a limited number of generations precludes establishment of highly integrated and biologically regulated communities by co-evolution. Dramatic shifts in species composition of eastern deciduous forests of North America occurred in prehistory and continue into the present. Similar changes are noted in the constant assembling and reassembling of species in the purportedly ancient and stable forests of the tropics. Numerous introductions with few extinctions in the flora of California have increased species richness and probably diversity, and many recent additions are primary contributors to ecosystem productivity. Recognition that rangeland ecosystems persist in unstable rather than stable species compositions provides both a challenge and an opportunity for natural resource management. The challenge is to develop new management principles that incorporate nonequilibrium theory. The opportunity is the promotion of policies and regulations that more closely reflect reality.
    • Declining forage availability effects on utilization and community selection by cattle

      Smith, M. A.; Rodgers, J. D.; Dodd, J. L.; Skinner, Q. D. (Society for Range Management, 1992-07-01)
      Land managers of salt desert shrub and sagebrush steppe vegetation have concerns regarding appropriate stocking rates in summer for ephemeral stream riparian zones because of elevated levels of use on woody vegetation. We determined utilization levels of forage species over time as a fixed animal density decreased available forage as a means of approximating the stocking rate suitable for an area and identifying plant species for monitoring. Trend in abundance of important plant species will ultimately determine appropriate stocking rate in a particular management situation. Forage utilization by cattle during mid-summer for 2 successive years was measured weekly for 3 weeks in streamside (channel and floodplain) and adjacent upland (terrace and saline upland) vegetation communities along the ephemeral stream. Measures were also made of crude protein and dry matter content of plant species. Plant communities used by cattle were also recorded. Utilization of streamside and terrace vegetation declined markedly over the 3 weeks, while utilization of forage in saline uplands was lower than in other areas and did not decline over weeks of study. More cattle selected streamside and terrace areas with the most succulent forages than saline uplands with less succulent forages. Woody plants in channel areas, cottonwood (Populus deltoides Bartr. ex Marsh.) particularly, were higher in protein, more succulent, and more severely grazed than other species. Management of cottonwood probably limits the stocking rate used in these communities. Declines in weekly utilization of forages after the first week indicated intake may have been declining. If so, lower levels of utilization may be needed to maintain animal performance. Maintenance of cottonwoods and animal performance considerations may dictate a lower stocking rate than achieved in this midsummer study.
    • Avian community response to fire and mechanical shrub control in south Florida

      Fitzgerald, S. M.; Tanner, G. W. (Society for Range Management, 1992-07-01)
      Effects of prescribed fire and roller chopping applied in 2 seasons on woody vegetation and the associated avian community of a southwestern Florida former dry prairie were studied. There were 5 vegetation treatments with 2 replications of each; treatments were control, winter burn, winter chop, summer burn, and summer chop. Percent shrub cover was sampled with line intercept transects. Birds were censused 25 times using the variable circular plot method. Burning in either season reduced shrub cover temporarily; chopping in either season reduced shrub cover significantly and it remained reduced throughout the 15 months of this study. Bird species richness and abundance were similar in control and burn plots. Birds were not seen in summer chop plots up to 5 months posttreatment. Bird species richness and abundance remained low in both winter and summer chop plots. Bird species that were observed in chop plots were mostly open country, grassland inhabitants, indicating a trend toward prairie restoration.
    • Germination of bur buttercup seeds

      Young, J. A.; Martens, E.; West, N. E. (Society for Range Management, 1992-07-01)
      Bur buttercup (Ranunculus testiculatus Crantz) is an alien annual species that has spread rapidly through range and croplands in the western United States. This species is potentially poisonous and is currently a weed in cereal grain fields. We investigated the germination of the achenes (seeds). About 30% of the seeds of bur buttercup germinated without pretreatment, but only at cool to cold temperatures (maximum germination 28% at 5 degrees C). Germination was not enhanced by light, washing, or prechilling of seeds. Acid scarification for 25 minutes increased germination. Enrichment of the germination substrate with 0.289 mmol L-1 gibberellic acid (GA3) and 0.01 mol L-1 potassium nitrate (KNO3) synergistically enhanced the germination of acid scarified seeds. Incubation of seeds pretreated in this manner at 55 constant or alternating temperatures resulted in maximum germination of 70%. All temperature regimes with optimum germination (defined as not lower than the maximum observed and one-half its confidence interval at 0.01 level of probability) occurred at relatively cool temperatures. Temperatures above 30 degrees C greatly suppressed or inhibited germination. Embryonic plants dissected from the achene costs had 60% germination without additional pretreatment, but only at cool to cold incubation temperatures. The germination-dormancy requirements of bur buttercup seeds are obviously complex, but about 30% of the seeds appear adapted for germination at cold seedbed temperatures, which fits with the extreme ephemeral growth habit of the species.
    • Habitat selection by cattle along an ephemeral channel

      Smith, M. A.; Rodgers, J. D.; Dodd, J. L.; Skinner, Q. D. (Society for Range Management, 1992-07-01)
      Because of widespread concern about cattle grazing effects on riparian zones of public lands, seasonal habitat selection by cattle was studied along a cold desert area ephemeral waterway of northcentral Wyoming. Little is known of grazing effects on ephemeral streams compared to perennial streams. Cattle activity was monitored in small pastures and a surrounding large allotment in spring, summer, and fall. Observations included activity and habitat where it occurred. Concomitantly, utilization levels, protein content, and dry matter content of forages were determined in the small pastures. A higher percent of cattle selected channel and floodplain habitats than percent area of habitats while a lower percent of cattle selected upland habitat than percent of this habitat in the area. Utilization levels of forages except greasewood (Sarcobatus vermiculatus (Hook.) Torrey) in the floodplain were not greatly different among habitats. Protein and dry matter content of forages did not vary greatly among habitats, except greasewood had higher protein and lower dry matter than other species and received much higher use. Forage quality declined in summer and fall. Animal preference for channel habitat was attributed to more available forage in the channels. In contrast, selection of floodplains was due to succulence and high protein content of greasewood. Comparison of cattle selectivity between small pastures and the large allotment indicates that greater avoidance of upland areas by cattle is likely due to greater distances to drinking water in the large allotment.
    • Herbicide effects on cross timbers breeding birds

      Schulz, C. A.; Leslie, D. M.; Lochmiller, R. L.; Engle, D. M. (Society for Range Management, 1992-07-01)
      We censused breeding nongame birds on replicated 5- and 6-year post herbicide-treated (tebuthiuron and triclopyr) and untreated cross timbers rangeland in central Oklahoma. Twenty species of breeding birds were observed. No treatment effects were detected for total bird density, species diversity, or richness; however, species composition varied considerably among treatments. Control sites supported species associated with closed canopy woodlands, and treated sites supported species associated with brushy and prairie habitat. Generally, control sites had greater foliar cover, fewer snags, and less slash and herbaceous cover than treated sites. Densities of 6 of the 7 most abundant bird species were correlated variously with habitat variables. We concluded that changes in habitat structure resulted in differences in bird species composition among treatments.
    • Effects of defoliation, shading and competition on spotted knapweed and bluebunch wheatgrass

      Kennett, G. A.; Lacey, J. R.; Butt, C. A.; Olson-Rutz, K. M.; Haferkamp, M. R. (Society for Range Management, 1992-07-01)
      Spotted knapweed (Centaurea maculosa Lam.) is a noxious plant that has invaded many native ranges in the Northern Intermountain Region. Although the use of livestock to control knapweed is intuitively appealing, feasibility of the strategy has received little attention. This greenhouse study was conducted to evaluate response of spotted knapweed to defoliation, light, and competition. Although total knapweed biomass (g/plant) was not altered by defoliation treatments, several of the more severe treatments adversely affected root, crown, and final harvest foliage. Root and crown growth were also adversely affected by increasing competition from bluebunch wheatgrass (Pseudoroegneria spicata). Foliage, root, and crown growth of spotted knapweed increased significantly when plants received full, rather than half light. Spotted knapweed was less sensitive to defoliation than was bluebunch wheatgrass. Although the feasibility of using livestock to control spotted knapweed cannot be completely disregarded, data suggest that the knapweed would have to be selectively and repeatedly grazed during the growing season.
    • Effect of timing and intensity of first defoliation on subsequent production of 4 pasture species

      Leyshon, A. J.; Campbell, C. A. (Society for Range Management, 1992-07-01)
      Two simulated pasture studies were carried out at Swift Current, Sask., to determine the effects of date and height of first harvest in the year following establishment on the yield of 4 species in subsequent years. Altai wild ryegrass [Leymus angustus (Trin.) Pilger], Russian wild ryegrass [Psathyrostachys junceus (Fisch.) Nevski] and crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] were used in both studies; alfalfa [Medicago sativa L. ssp. X varia (Martyn) Arcangelil] was included in the second study only. In both studies plots were first cut at 1 of 6 dates, approximately 2 weeks apart, during the period from mid-May to late July in the year following establishment. Cuts were made either at a 5 cm or at a 10 cm height to simulate medium grazing and light grazing, respectively. After the first cut, forage was harvested in that year whenever 10 cm of regrowth was present. In the next 5 years in the first study and 3 years in the second, all forage was harvested at 5 cm height on 15 May and thereafter whenever 10 cm of regrowth was present. Treatment effects were greatest in the year treatments were imposed and in the first post-treatment year. In the treatment year, highest forage yields were obtained from plots cut at 5 cm, but in subsequent years, forage yields were higher from plots cut at 10 cm in the treatment year. Moisture conditions in the seeding and establishment years affected the response to treatments. Date of first cut in the treatment year affected yields in subsequent years in both experiments although differences declined with time. Crested wheatgrass was more affected by date of first cut than were the other species. The cutting dates for highest yields in each case correlated with flowering date and indicate that seedings of these grasses should not be harvested until they have flowered. The results of this study also indicate that to ensure continued high forage yields, the first harvest of these grasses should be less intense than subsequent harvests.
    • Mortality of crested wheatgrass and Russian wildrye during drought

      Haferkamp, M. R.; Currie, P. O.; Volesky, J. D.; Knapp, B. W. (Society for Range Management, 1992-07-01)
      From September 1987 through September 1988, the Northern Great Plains near Miles City, Mont., received 31% of the long-term average precipitation. We monitored the impact of the hot, dry conditions during the growing season on mortality of tillers and plants of 'Vinall' Russian wildrye (Psathrostachys juncea [Fisch.] Nevski) and 'Nordan' crested wheatgrass (Agropyron desertorum [Fisch.] Schult). Plants were collected in the field, watered, and placed in controlled environments. Ninety-two percent of the wildrye plants collected in July produced green shoots. Fifty-seven percent of the wheatgrass plants collected in July produced shoots. The maximum percentage of wildrye and wheatgrass plants producing green shoots in August was significantly (p less than or equal to 0.10) less than in July. Transects were used to sample density of dormant and live plants after September rains, and plants were incubated as before. When transect and incubation data were combined, only 41% of the wildrye and 16% of the wheatgrass plants were deemed viable in September.
    • Seasonal trends in herbage yield and quality of Agropyrons

      Mayland, H. F.; Asay, K. H.; Clark, D. H. (Society for Range Management, 1992-07-01)
      Crested wheatgrasses (Agropyron spp.) are grown on 6 million ha in the U.S. and Canada, where they provide excellent early-season forage, but lose nutritional quality by midsummer. Some producers believe that A. fragile maintains its quality longer than other crested wheatgrasses. This study compared herbage yield and quality of 3 A. fragile entries with A. desertorum, A. cristatum, I-28 (induced tetraploid of A. cristatum), and the hybrid 'Hycrest'. Entries were established near Logan, Ut., on 1-m spacings. Herbage yield and quality were determined in year 2 and 3 at vegetative, boot, flower, seed ripe, and post-seed-ripe maturity stages (harvests 1 through 5) and on regrowth following the vegetative and boot-stage harvests. All entries flowered within 1 to 2 days of each other. Dry-matter yield increased for all grasses, but digestibility (IVDMD), crude protein, and elemental concentrations declined with maturity. Mean IVDMD values for all grasses were 741, 642, 534, 485, and 444 mg g-1 for harvests 1 through 5 and 490 and 560 mg g-1 for the regrowth following harvest 1 and 2. The A. fragile entries had higher N, Ca, P, and Ca/P, but lower yield, IVDMD, and grass tetany potential values than other Agropyrons. Contrary to expectations, IVDMD of A. fragile decreased to 500 mg g-1, 6 to 11 days earlier than for the other Agropyrons. The I-28 and Hycrest entries had higher yield, IVDMD, K, and grass tetany risk and lower N, Ca, P, and Ca/P than the other Agropyrons.
    • Influence of leafy spurge on forage utilization by cattle

      Hein, D. G.; Miller, S. D. (Society for Range Management, 1992-07-01)
      A 3-year field study was conducted near Grassrange, Montana. (Latitude 46 degrees 50'N and Longitude 108 degrees 50'W) to determine the effect of leafy spurge (Euphorbia esula L.) shoot density, control, and canopy cover on the utilization of forage by cattle. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) was applied at 0.28 to 2.24 kg ae/ha on leafy spurge-infested native pasture to establish different levels of leafy spurge shoot density and canopy cover. Utilization of forage was influenced by leafy spurge shoot density (r = -0.65) and canopy cover (r = 0.87) and was not related to the amount of forage (r = -0.1) produced. A leafy spurge canopy cover of 10% or more and a leafy spurge shoot control value of 90% or less resulted in a significant decrease in utilization of forage by cattle.
    • Response of cattle to cured reproductive stems in a caespitose grass

      Ganskopp, D.; Angell, R.; Rose, J. (Society for Range Management, 1992-07-01)
      Accumulation of wolf plants in rangeland pastures frequently results in waste or incomplete utilization of high quality forage by cattle. The objective of this research was to establish the degree of sensitivity of cattle to cured stems in crested wheatgrass (Agropyron desertorum (Fischer ex Link) Schultes) at 3 stages of phenology (late-boot, anthesis, and quiescence). This was accomplished by providing individual plants having densities of 0, 3, 6, 9, or 12 cured stems per dm2 basal area and measuring frequency and degree of utilization after exposure to cattle grazing. Project design was a split-plot in a randomized complete block with 3 replications, 3 stages of phenology as whole plots, and 5 densities of stems as treatments. A significant (P<0.01) phenology X treatment interaction occurred with cattle being equally sensitive to all treat- ments containing stems at late-boot and anthesis and oblivious to their presence at quiescence. At late-boot and anthesis stages of phenology 75% of plants with no stems were grazed while only 45% of plants with stems were grazed. Respective levels of utilization from the same treatments were 25 and 8%. A negative response was exhibited by cattle during anthesis when as little as 4% of biomass was contributed by cured stems. These results suggest that old growth stems should be removed or their presence noted as a covariate when conducting palatability studies or when observing plant-specific responses to defoliation by cattle. Cattle were not sensitive to treatments at quiescence when roughly 75% of plants in all treatments were defoliated with 25% herbage removal. This suggests that heavy grazing of a pasture with an objective of obtaining utilization of wolf plants would be most successful after all forage has cured, and cattle are less selective.
    • Value of mountain rye for suppression of annual bromegrasses on semiarid mined lands

      Andersen, M. R.; Depuit, E. J.; Abernethy, R. H.; Kleinman, L. H. (Society for Range Management, 1992-07-01)
      The value of mountain rye (Secale montanum Guss.) for competitive suppression of 2 annual bromegrasses (downy brome, Bromus tectorum L. and Japanese brome, B. japonicus Thunb) was investigated in a 3-year study on reclaimed coal mined lands in southeastern Montana. Rye established rapidly and vigorously, but did not persist appreciably (either through initially established plants or new seedlings) after the second year. However, mountain rye significantly reduced growth and reproduction of annual bromes during the first 2 growing seasons. Mountain rye also inhibited growth of other concurrently seeded perennial grasses during the first 2 seasons. Annual brome soil seedbanks were not sufficiently reduced in rye-seeded plots to prevent an eventual, third year recovery of brome productivity after a massive dieback of rye between the second and third growing seasons. Mountain rye therefore proved effective for short but not for longer-term control of annual bromes. This study did not allow distinction between the known short-lived nature of mountain rye and/or local environment as causal factors for the massive dieback after the second year.
    • Honey mesquite transpiration along a vertical site gradient

      Cuomo, C. J.; Ansley, R. J.; Jacoby, P. W.; Sosebee, R. E. (Society for Range Management, 1992-07-01)
      Honey mesquite (Prosopis glandulosa Torr.) occurs on a variety of sites varying in soil depth and moisture availability. The objective of this study was to compare water use by honey mesquite on upland, lowland, and riparian sites which were assumed to represent increasing levels of available soil moisture within a single watershed. Effects of the upland and lowland sites were evaluated in 1985. The riparian site was evaluated with the other 2 sites in 1986. Soil moisture and average daily transpiration were greater (P < 0.05) on the upland than on the lowland site from mid-May to July in both years, and from mid-August through September 1986. These differences were attributed mainly to soil surface characteristics which created greater infiltration on the upland site. The riparian site was near an ephemeral stream and had a water table as shallow as 1.5 m. Soil water content was much greater for this site compared to the other 2 sites throughout 1986. Mesquite transpiration was greater on the riparian site than on the other sites during July 1986, when seasonal vapor pressure deficit was at maximum. However, transpiration was less on the riparian site than on the upland site during May and June 1986. Soil temperature was significantly lower on the riparian than on the upland site and potentially inhibited transpiration on the riparian site in May and June. The study demonstrated a positive relationship between water availability and transpiration by mesquite but did not support the hypothesis that water availability or transpiration was lowest on upland sites.
    • Some effects of a white grub infestation on northern mixed-grass prairie

      Lura, C. L.; Nyren, P. E. (Society for Range Management, 1992-07-01)
      Graminoid standing crop in June 1985 on areas infested with white grubs (Phyllophaga anxia Leconte) (average density = 47 grubs m-2) was 92% less than on uninfested rangeland (average density < 2 grubs m-2). Study area was the Central Grasslands Research Center in south-central North Dakota. Infestations were noticeably associated with communities dominated by western snowberry (Symphoricarpos occidentalis Hook.) with an understory subdominance of Kentucky bluegrass (Poa pratensis L.). The objective of our study was to assess the initial impact and subsequent recovery of infestation on community standing crops and plant densities. Mid and late summer standing crops of Kentucky bluegrass and other grasses were significantly less (P < 0.05) on infested than uninfested sites between 1985 and 1987. Graminoid density was less (P < 0.05) on infested than uninfested sites during 1985 and 1986. Post-infested standing crop and density of forbs increased (P < 0.05) on infested sites. Infestation of sites subsequently provided habitat for establishment of noxious weeds such as wormwood sage (Artemisia absinthium L.). Management techniques to enhance the recovery of grasses and eliminate establishment of noxious weeds may be necessary.
    • Time domain reflectometry for measuring soil water content in range surveys

      Reeves, T. L.; Smith, M. A. (Society for Range Management, 1992-07-01)
      Time Domain Reflectometry (TDR) is introduced as a viable alternative for measuring soil water content for rangeland surveys. The method is based on a strong relationship between the complex dielectric constant of soil and volumetric soil water. Volumetric water content, measured by TDR and gravimetrically, was compared for 2 rangeland sites. TDR underestimated volumetric water content when compared to gravimetric samples for all data. Potential causes of this error and possible solutions are discussed. Some advantages and disadvantages of the method are discussed.
    • Seasonal trends in leaf area of honey mesquite trees: Determination using image analysis

      Ansley, R. J.; Dowhower, S. L.; Carlson, D. H. (Society for Range Management, 1992-07-01)
      Black-and-white photographs were used to estimate seasonal trends in whole plant leaf area of honey mesquite (Prosopis glandulosa var. glandulosa Torr.) trees occurring on a site with limited subsurface water. Height and canopy width of the trees ranged from 1 to 5 m and 1 to 7 m, respectively. Images consisted of profile-view angles of trees occurring on flat terrain. Four image variables, height, width, canopy profile perimeter length, and canopy profile area were obtained from the photographs and used to predict leaf area of unharvested trees. Predictive equations were based on adjacent trees which were photographed and harvested for actual leaf area determination. Canopy profile area was evaluated as the most accurate image variable for predicting leaf area. Whole plant leaf area of unharvested trees varied within and between growing seasons and was dependent on precipitation patterns. During the 1987 growing season, leaf area declined significantly by 14.6% from 17.1 m2 (1 leaf surface) in May to 14.6 m2 in August, in conjunction with a mid-summer dry period. Leaf area increased in September 1987 in response to late-summer precipitation. Leaf area was less in the spring of 1988 than the spring of 1987 because of lower precipitation during the winter prior to the 1988 than the 1987 growing season. Leaf area did not decline significantly from spring to mid-summer in 1988 as it did the previous year because of atypically high precipitation in July 1988. Leaf area did not increase in September of 1988 as it did in 1987 because of lack of late-season rains in 1988. These results suggest mesquite on this study site used partial leaf shedding to augment drought resistance.
    • Selenium absorption by two-grooved milkvetch and western wheatgrass from selenomethionine, selenocystine, and selenite

      Williams, M. C.; Mayland, H. F. (Society for Range Management, 1992-07-01)
      Selenium (Se) occurs in various forms in soils, including inorganic selenite and selenate and organic selenomethionine. Plant uptake of the inorganic, but not the organic forms, has been studied extensively. Organic-Se uptake was therefore examined in two-grooved milkvetch (Astragalus bisulcatus (Hook.) Gray), a Se-accumulating forb, and western wheatgrass (Pascopyrum smithii (Rydb.) Löve), a non-Se accumulating grass. Plants were grown for 56 days in nutrient culture enriched with 1 or 2 mg Se liter-1 as sodium selenite or 0.3 or 0.6 mg Se liter-1 as Se-DL-methionine or Se-DL-cystine. Growth was not affected by the Se treatments. Selenium concentrations in shoots were proportional to nutrient-solution concentrations for both species grown in sodium selenite and selenocystine, and for wheatgrass when grown in selenomethionine. Selenium concentrations in milkvetch were not increased by the higher concentration of selenomethionine. Shoots of milkvetch, growing in the low-Se treatment contained 243, 283, and 47 micrograms Se g-1, for the sodium selenite, selenomethionine, and selenocystine treatments, respectively, whereas values for the wheatgrass were 20, 32, and 17. Shoot:root Se concentrations were 1.2, 0.7, and 0.4 in milkvetch and 0.1, 0.5, and 0.1 in wheatgrass for the sodium selenite, selenomethionine, and selenocystine, respectively. Selenium is more readily transported to shoots in the accumulator plant, or conversely; there is a barrier to Se movement to shoots in the nonaccumulator plant. Wheatgrass contained sufficient Se to be of concern in animal toxicosis and because of greater dry matter yield accumulated as much or more Se than did the milkvetch.