• Defoliation Effects on Three Range Grasses

      McLean, Alastair; Wikeem, Sandra (Society for Range Management, 1985-04-01)
    • Defoliation effects on yield and bud and tiller numbers of two Sandhills grasses

      Mullahey, J. J.; Waller, S. S.; Moser, L. E. (Society for Range Management, 1991-05-01)
      Intensive grazing strategies for the Nebraska Sandhills must be based on time and frequency of defoliation of key warm-season grasses. A 3-year field study was conducted in the Nebraska Sandhills to determine the effects of defoliation on yield and bud and tiller number of sand bluestem [Andropogon gerardli var. paucipilus (ash) Fern.] and prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.]. Defoliation (7 cm) treatments imposed on a 1.5 X 1-m plot were: a single defoliation on 10 June, 10 July, or 10 August; 2 successive defoliations on 10 June and 10 August; or 3 successive defoliations on 10 June, 10 July, and 10 August. All plots were harvested in October to obtain aftermath yield. Control plots were harvested only at the end of the growing season (October). Defoliation treatments were initiated in 1986, 1987, and 1988 on different plots and the effect of year of initiation as well as the effect of 3 successive years of repeated treatment (1986 plots) was evaluated. Annual dry matter (DM) yield, and bud and tiller numbers were measured. Following the initial year of treatment multiple defoliations increased yield of both grasses while bud and tiller numbers were similar to those of the control plants. After 3 years of repeated treatment, annual DM yield of sand bluestem for all defoliation treatments was lower than the control. A single defoliation of sand bluestem in August or a June-July-August defoliation reduced bud number compared to other treatments and the control. A June-August defoliation of prairie sandreed over a 3-year period increased annual DM yield compared to all treatments and the control although defoliation treatments reduced bud number. The optimum time and frequency of defoliation for annual DM yield and bud and tiller number was a single June or July defoliation for sand bluestem and a June-August defoliation for prairie sandreed.
    • Defoliation frequency and intensity effects on pasture forage quality

      Motazedian, I.; Sharrow, S. H. (Society for Range Management, 1990-05-01)
      Both quantity and quality of pasture forage produced generally varies with frequency and intensity of plant defoliation. However, intensity and frequency of defoliation have rarely been evaluated simultaneously. The objective of this study was to quantify forage quality response to simultaneous changes in defoliation treatments over a range of values likely to occur in short-duration graxing systems. Effects of defoliation treatments on forage digestibility (DMD), crude protein content (CPC), crude protein yield, and digestible dry matter yield were evaluated on a perennial ryegrass (Lolium perenne, L.)-subclover (Trgolium subterraneum L.) hill land pasture growing on a Ultic Hapioxeroll soil near Corvallis, Oregon. Treatments consisted of all possible combinations of 4 defoliation intervals (clipped every 7, 21, 35, or 49 days) and 3 stubble heights (High-70, Medium-55, or Low-40 mm of stubble remaining after defoliation) applied during the 1980, 1981, and 1982 growing seasons. Digestible dry matter yield increased with increasing defoliation interval. With the exception of DMD in 1980, both digestibility and CPC of the forage produced decreased linearly as the period between defoliation events Increased. Crude protein content increased linearly as stubble height Increased, while forage digestibility was comparatively insensitive to changes in stubble height. Forage quality was generally adequate on all treatments to meet the needs of most classes of livestock.
    • Defoliation impacts on coppicing browse species in northeast Brazil

      Hardesty, L. H.; Box, T. W. (Society for Range Management, 1988-01-01)
      A study was conducted to determine if manually cutting coppice growth from the stump once or twice in the first growing season, exposing the coppice to 2 periods of intensive goat browsing, or no defoliation of coppice caused mortality or compensatory growth in 4 tree species of the Brazilian caatinga. Sabia' (Mimosa caesalpinia), and catingueira (Caesalpinia pyramidalis) suffered no mortality regardless of treatment, but pau branco (Auxemma oncocalyx), and marmeleiro (Croton hemiargyreus) that were browsed or manually defoliated experienced significant mortality. In the year of treatment undefoliated and browsed trees of all species produced significantly more stem material than manually defoliated plants. Browsed catingueira produced more leaf material than undefoliated or manually defoliated plants. The year after treatment, undefoliated trees produced more leaf and stem than either browsed or manually defoliated trees. Normally pau branco and marmeleio are not browsed and both species suffered significant mortality after manual or browsing defoliation, suggesting they are not adapted to herbivory; whereas intact sabia' and catingueira are palatable and suffered no mortality following browsing or removal of coppice. Undefoliated trees produced more biomass than browsed or manually defoliated trees; thus, removal of coppice growth does not stimulate increased forage production. Browsed trees produced regrowth during the dry season when these species are normally leafless. Manually defoliated trees did not, highlighting the fact that trees respond to browsing differently than to manual defoliation. This study demonstrates that regenerating caatinga stands can be manipulated through browsing or manual defoliation of coppice to achieve specific management objectives.
    • Defoliation impacts on Festuca campestris (Rydb.) plants exposed to wildfire

      Bogen, A. D.; Bork, E. W.; Willms, W. D. (Society for Range Management, 2003-07-01)
      Wildfires commonly occur in the Fescue Prairie of Alberta, but little information exists to provide a basis for making grazing recommendations after burning. A wildfire in April 1999 provided an opportunity to study the effect of season and intensity of post-burn defoliation on foothills rough fescue (F. campestris Rydb.) in southwestern Alberta. A 3 (date of defoliation) x 2 (defoliation intensity) factorial experiment with 10 replicates (plants) was established in both a burned and a non-burned grassland and analyzed as a nested design. Plants were defoliated once during active vegetative growth (17 May), inflorescence development (2 July), or dormancy (30 September), at either 5 or 15-cm clipped stubble heights in the first growing season after fire. Burning increased tiller numbers by 54% compared to non-burned plants but reduced plant ANPP by 51% in the second growing season. While a single defoliation of burned plants, particularly early in the year, had little effect on growth, delaying defoliation into July decreased tillers 1 year later. Increasing defoliation intensity had the greatest impact on non-burned plants, reducing plant height (15%) as well as tiller (21%) and plant (32%) ANPP in the second year. May defoliation reduced etiolated growth 1 year later regardless of burn treatment. A single grazing event after wildfire does not necessarily appear to detrimentally affect rough fescue; however, the low herbage available immediately after fire may not justify the increased risk to the plant with subsequent grazing.
    • Defoliation Impacts on Quality and Quantity of Forage Harvested from Big Sacaton (Sporobolus wrightii Munro)

      Haferkamp, M. R. (Society for Range Management, 1982-01-01)
      Forage quality and quantity and stand vigor of big sacaton were evaluated for seven defoliation systems during 1977 and 1978. Big sacaton plants were either shredded monthly, shredded in spring/midsummer, spring/early summer, spring, spring/late summer/fall, midsummer/fall, or late winter. Forage quality of big sacaton was improved by defoliation during both years. With few exceptions, crude protein content was highest in plants defoliated the previous month. IVDOM contents were also improved by defoliation. Digestibility decreased to below 50% in early summer in nonshredded plants and in mid summer in all plants regardless of prior defoliation treatment. IVDOM increased to above 50% in late summer and fall in plots defoliated the previous month. Forage harvests during the growing season were greatest from plots that were defoliated three or more times and were defoliated in the fall. The least amounts of forage were harvested from the plots defoliated in spring, spring/early summer and spring/midsummer. In the fall and winter the nonshredded and spring defoliated plots supported relatively large amounts of forage, and the spring/early summer and spring/midsummer plots supported intermediate amounts of forage for winter grazing. Stand vigor was maintained best by brief periods of defoliation in the spring or spring/early summer, followed by defoliation of old forage in late winter. Vigor appeared to be decreased by early fall defoliations to a 7.5 cm stubble height. The spring/early-summer system provided large amounts of high quality forage and maintained stand vigor. This system defoliated plants when soil moisture was usually adequate for plant regrowth, provided nutritious forage during the growing season and provided adequate standing forage for fall and winter grazing and protection against damage due to low temperature.
    • Defoliation increased above-ground productivity in a semi-arid grassland

      Loeser, Matthew R.; Crews, Timothy E.; Sisk, Thomas D. (Society for Range Management, 2004-09-01)
      In light of the continuing debate regarding overcompensation we studied the responses of above-ground biomass in a high-elevation, semi-arid grassland to defoliation, defoliation history, and livestock grazing. The above-ground annual net primary productivity (ANPP) was measured over 2 years in one-hundred twenty, 1-m2 plots that were exposed to single- and multi-year defoliation and grazing treatments. Plant communities showed an average increase in ANPP of 31%-45% due to a single defoliation event. The most conservative estimate of average ANPP of defoliated subplots was 29.4 g m-2 greater than the non-defoliated controls. A history of defoliation, due to clipping or grazing, lessened the magnitude of the compensatory response, but above-ground overcompensation of biomass was still observed, ranging on average from 17% to 26%. One dominant species, squirreltail grass [Elymus elymoides (Raf.) Swezeyi], accounted for nearly one-third of the community-level increases in ANPP. In contrast to above-ground patterns, below-ground root production of squirreltail did not increase in response to defoliation events. These results suggest that the above-ground production of high-elevation, semi-arid grasslands in the American Southwest may be temporarily increased through certain grazing events, and may help explain shifts in species dominance in grasslands exposed to long-term grazing by livestock.
    • Defoliation of a northern wheatgrass community: Above- and belowground phytomass productivity

      Zhang, J.; Romo, J. T. (Society for Range Management, 1994-07-01)
      A defoliation study was conducted on a fair condition, clayey range site that is potentially dominated by northern wheatgrass (Agropyron dasystachyum (Hook.) Scribn.) in south-central Saskatchewan. Vegetation was subjected to a factorial experiment with an initial defoliation in early-May, June, July, or August and repeated at 2- or 6-week intervals until mid-September in the same plots for 3 years. An undefoliated control was also included. Herbage removed, residual live, dead, total and root phytomass were measured. Defoliation reduced all yield components, with the exception of herbage removed. Residual live grass was reduced 37, 57, and 46%, respectively, in first second, and third years; the sedge and forb components of live residual phytomass generally were not affected by defoliation. Compared to control, dead phytomass was reduced 77% in the first year, 67% in the second, and 52% in the third year across treatments. Total herbage yield across defoliation treatments ranged from 68 to 93% of control Total live phytomass (herbage removed + residual live phytomass) in defoliated plots equaled control Herbage removal was greatest when initially defoliated in early July and thereafter at 2-week intervals. When defoliated at 6-week intervals residual live and dead phytomass were generally greater than when herbage was removed biweekly. Yields were higher when the first defoliation was delayed and repeated at 6-week intervals. Generally, root phytomass was not different among defoliation treatments, but total belowground phytomass was reduced 30% in the 0-30-cm depth after 3 year of defoliation. This northern mixed prairie ecosystem is sensitive to herbage removal. Maximum forage yield can be obtained if grazing is deferred until after peak growth in July.
    • Defoliation of Intermediate Wheatgrass Under Seasonal and Short-Duration Grazing

      Pierson, F. B.; Scarnecchia, D. L. (Society for Range Management, 1987-05-01)
      Defoliation of intermediate wheatgrass (Agropyron intermedium by cattle was examined under seasonal and short-duration grazing. Tiller height, number of green leaves per tiller, phenological status, and defoliation frequency were measured on individually marked tillers during 2 grazing seasons. Defoliations at high and low stocking densities (5.2 and 2.6 animal-units/ha) were examined during the 1983 growing season. At equal stocking rates, standing crop decreased more rapidly under low stocking density. Mean tiller height and mean number of leaves per tiller decreased linearly over time in both treatments. In 1984, 14 heifers were moved through 3 rotations of an 8 subunit short-duration grazing system in 72 days. A larger fraction of tiller height and a higher number of green leaves per tiller were defoliated during rotation one than during rotation three. Animals grazed the greatest number of tillers during rotation one. Biting rate varied logarithmically with the mean number of green leaves per tiller. Time spent grazing was significantly and inversely related to the mean number of green leaves per tiller. This result suggests that animals were selectively grazing green leaves over coarse stem, and spent more time searching for them as their numbers decreased.
    • Defoliation of Thurber needlegrass: herbage and root responses

      Ganskopp, D. (Society for Range Management, 1988-11-01)
      Thurber needlegrass (Stipa thurberiana Piper) is an important component of both forested and shrub-steppe communities of the Pacific Northwest and Great Basin regions, and little is known of its tolerance to defoliation. A study was conducted on the Squaw Butte Experimental Range to determine the response of containerized Thurber needlegrass to single defoliations (2.5-cm stubble) throughout the growing season. Dates of treatment spanned vegetative through quiescent stages of phenology. Response variables included: summer regrowth, number of reproductive stems, fall growth, and subsequent spring herbage production, change in basal area, and root mass. Vigor of Thurber needlegrass was reduced most by defoliation during the early-boot stage of development. Impacts were successively less severe from vegetative, late-boot, and anthesis treatments, respectively. Cumulative herbage production the year of treatment was reduced from 38 to 64% by defoliation at the early-boot stage. The same treatment reduced subsequent spring growth by 46 to 51% and root mass the next spring by 34 to 45%. Treatment effects were somewhat reduced when temperature and moisture regimes allowed substantial regrowth after defoliation. Defoliation during or after anthesis had little effect on plant response. Managers should be aware that a single defoliation, particularly during the boot stage, can significantly reduce subsequent herbage production and root mass and possibly lower the competitive ability of Thurber needlegrass.
    • Defoliation Response of Bluebunch Wheatgrass and Crested Wheatgrass: Why We Cannot Graze These Two Species in the Same Manner

      Meays, Cindy L.; Laliberte, Andrea S.; Doescher, Paul S. (Society for Range Management, 2000-12-01)
    • Defoliation time and intensity of wall barley in the Mediterranean rangeland

      El-Shatnawi, M. K. J.; Ghosheh, H. Z.; Shannag, H. K.; Ereifej, K. I. (Society for Range Management, 1999-05-01)
      Wall barley (Hordeum murinum L.) is the dominant species in northeastern rangeland of Jordan that decreases under grazing. We investigated the responses of wall barley to clipping time and height during 2 growing seasons in the semiarid rangeland of Jordan. A natural stand was utilized to conduct the experiments that were arranged in a randomized complete block design during 1994/95 and 1995/1996 growing season. Treatments were combinations of clipping heights (5 or 10 cm above soil surface) and plant growth stages (tillering, jointing, or booting), in addition to unclipped check. Results showed that clipping to 5 and 10 cm stubble height at tillering produced 1,167 and 1,349 kg ha(-1) dry matter, respectively, compared to 1,122 kg ha(-1) for unclipped check. Clipping to 5 and 10 cm stubble height reduced shoot weight by 28 and 21% at jointing stage and 52 and 38% at booting stage. Defoliation during tillering stage did not impact plant height of regrowth nor seed yield. Weed biomass were higher when plant defoliation was delayed to the jointing and booting stages. Therefore, it is recommended to defoliate wall barley early at tillering stage but before plants reach jointing or reproductive stages.
    • Defoliation Timing Effects on Spotted Knapweed Seed Production and Viability

      Benzel, Katie R.; Mosley, Tracy K.; Mosley, Jeffrey C. (Society for Range Management, 2009-11-01)
      Spotted knapweed (Centaurea stoebe L.), a perennial invasive forb that reproduces largely by seed, often forms new flowers after prescribed sheep grazing or mowing is applied during the bolting or flowering stage. It is unknown if these new flowers produce viable seeds by the end of the growing season. The purpose of this 2-yr study was to determine the appropriate timing (or timings) or combination (or combinations) of timings of defoliation on spotted knapweed to reduce its viable seed production. Spotted knapweed plants on foothill rangeland in west-central Montana were hand-clipped at seven different timings and frequencies of defoliation: June (bolting stage); July (late-bud-early flowering stage); August (full-flowering stage); June + July; June + August; July + August; or June + July + August. Unclipped plants were controls. Plants clipped in the bolting stage were defoliated at 35-40% relative utilization. Plants clipped at all other timings had 100% of their buds and flowers removed, plus 3 cm of each bud or flower stem. Plant response was evaluated from mid-August through September, whenever the seed heads of each treatment’s plants reached maturity but while their seed-head bracts remained tightly closed. Clipping at any timing or combination of timings reduced the number of buds and flower heads per plant (P < 0.01), number of seeds per plant (P < 0.01), percentage of viability of seeds (P < 0.01), and number of viable seeds per plant (P < 0.01) compared with no clipping. Clipping during the bolting stage reduced the number of viable seeds by nearly 90% compared with no clipping. Clipping during the late-bud-early-flower or full-flower stage reduced the number of viable seeds by nearly 100% compared with no clipping. Spotted knapweed defoliation via prescribed sheep grazing or mowing in summer should suppress viable seed production of spotted knapweed. 
    • Defoliation tolerance and ammonium uptake rate in perennial tussock grasses

      Carolina, Saint Pierre; Busso, Carlos Alberto; Montenegro, Oscar; Rodriguez, Gustavo D.; Giorgetti, Hugo D.; Montani, Tomas; Bravo, Oscar A. (Society for Range Management, 2004-01-01)
      Stipa clarazii, Ball. has been shown to be more tolerant to defoliation and a superior competitor to S. tenuis Philo and S. ambigua Speg. 3 perennial grasses native to semiarid rangelands in central Argentina. Mechanisms contributing to its great defoliation tolerance and competitive ability, however, are largely unexplored. We examined tolerance to defoliation and ammonium uptake rates on defoliated and undefoliated plants of those species at 10, 25, and 50 ppm NH4+ using (NH4)2SO4 solutions containing 60 atom %15N excess. By mid-spring, greater regrowth following defoliation in S. clarazii than in S. tenuis or S. ambigua indicated greater defoliation tolerance in the first than in the other 2 species. Stipa clarazii had similar of higher ammonium uptake rates than S. tenuis and S. ambigua. Higher ammonium uptake rates in S. clarazii thus appear to be one of the mechanisms most likely contributing to its greater competitive ability and defoliation tolerance when compared to the other 2 species. Defoliated plants of all 3 species had similar or greater ammonium uptake rates than undefoliated plants. These results suggest that photosynthetic canopy reestablishment may be achieved without sacrificing root function in these perennial grasses, at least as long as carbon reserves do not become a limiting factor. Ammonium uptake rates increased when NH4+ concentrations increased in the labeled solutions in S. clarazii, S. tenuis and S. ambigua. This result demonstrates the capacity of the root system for increasing nutrient acquisition during periods of high resource availability.
    • Defoliation, waterlogging and dung influences allocation patterns of Deschampsia caespitosa

      Merrill, E. H.; Colberg, P. J. S. (Society for Range Management, 2003-11-01)
      Wet meadows are some of the most productive communities in the northern Rocky Mountains, USA but are also among the most sensitive to grazing by native ungulates and domestic livestock. These meadows typically are inundated with floodwater in spring and early summer but are relatively dry in summer. To determine the interactive effects of clipping and flooding on plant recovery after clipping, we subjected plants of tufted hairgrass (Deschampsia caespitosa (L.) Beauv) to 6-week and 10-week waterlogging treatments in combination with 1 and 2 clipping events, with and without dung amendment in a greenhouse experiment. The experiment was designed to mimic early and late growing-season patterns of herbivory by native and domestic herbivores on a dominant species of wet meadows of this region. Waterlogged plants produced a higher percentage of roots at the surface, elongated stems to the first axial leaf, increased the proportion of tillers that flowered, but increased aboveground yield and tiller height only with the addition of dung. Root biomass declined with waterlogging when dung was not added, and a second defoliation exacerbated the negative effects of waterlogging on roots. Defoliation with short-duration waterlogging increased shoot nitrogen (N) concentration and N yield/root biomass, while continuous waterlogging reduced shoot N concentration of aboveground biomass. Dung amendment did not reverse this effect. Although extended flooding in combination with moderate rates of defoliation did not reduce aboveground biomass of Deschampsia caespitosa, it aggravated total root loss, caused shifts to a shallower root distribution, and altered N concentration of aboveground biomass for herbivores.
    • Deformed Calves From Poisonous Plants

      Keeler, Richard F. (Society for Range Management, 1983-10-01)
    • Degradability of Andrean range forages in llamas and sheep

      Genin, D.; Tichit, M. (Society for Range Management, 1997-07-01)
      In sacco dry matter degradability (DMD) of the most commonly consumed range forages by llamas and sheep in the arid highlands of Bolivia was measured during the wet and dry seasons to determine if llamas exhibit a higher digestive ability than sheep. Results showed that degradability of low quality forages (DMD below 60% in sheep) was 20 to 30% higher for llamas than sheep, while no significant differences were found for highly digestible forages. There was a high correlation between DMD in llamas and sheep with a coefficient of determination of 0.96. Parameters of degradation curves indicated that llamas did not have higher microbial activity than sheep, since there was no consistent difference in degradation rates of the studied forages. Nonetheless, significantly higher potential degradability and effective degradability found in this study suggested that the longer retention time in the forestomach of llamas may be responsible for higher digestibility of poor quality forages.
    • Dehydration effects on seedling development of four range species

      Bassiri, M.; Wilson, A. M.; Grami, B. (Society for Range Management, 1988-09-01)
      The effects of temporary drought periods of semiarid regions were simulated by dehydration of germinating seeds of crested wheatgrass (Agropyron desertorum), Russian wildrye (Elymus junceus), alfalfa (Medicago sativa), and cicer milkvetch (Astragalus cicer) in 8 constant humidity environments, ranging from -10 to -220 MPa for 4 days. Combined effects of root excision and temporary dehydration at -22 to -160 MPa were also studied. Subsequent growth of seedlings was evaluated in growth performance tests under favorable soil moisture conditions. When the initial roots were killed by dehydration, survival of grasses depended on the development of seminal lateral root(s) from the scutellar nodes, and survival of legumes depended on development of a new meristem at the distal end or along the side of hypocotyl-root axis. The effect of dehydration was more drastic on the legumes than on the grasses, particularly at more severe conditions. While temporary dehydration of -59 MPa had little effect on grasses, it reduced the percent emergence of the legumes by about 70%. In the -220 MPa treatment, emergence percentages of crested wheatgrass, Russian wildrye, alfalfa, and cicer milkvetch were 59, 35, 6, and 1, respectively, and percentages of rooted seedlings were 58, 12, 3, and 1, respectively. Under combined effects of excision and dehydration at -160 MPa, emergence percentages of the 4 species were 50, 34, 14, and 0, respectively, and their root lengths decreased by 37, 42, 44, and 100%, respectively. Within species variation in tolerance of dehydration suggested opportunities to select and breed for this characteristic.
    • Del River Farm—The Evolution of a Louisiana Grazing Enterprise

      Mattox, Matthew (Society for Range Management, 1998-06-01)
    • Delayed Calving in Wyoming

      May, Gary J.; Van Tassell, Larry W.; Smith, Michael A.; Waggoner, James W. (Society for Range Management, 1999-04-01)