• Effects of dormant-season herbage removal on Flint Hills rangeland

      Auen, L. M.; Owensby, C. E. (Society for Range Management, 1988-11-01)
      Stocking rate effects on intensive-early stocked Kansas Flint Hills range were studied from 1982 through 1987. Rates were 2X, 2.5X, and 3X normal season-long stocking rates for 200-225 kg steers. Study design was a randomized complete block with 2 replicates. Grass and forb standing crop (kg/ha) were estimated at the time of livestock removal (mid July) and again in early October. Plant basal cover and composition were taken in early June the year prior to the study and annually thereafter. Overall growing season precipitation during the study period was below normal, with late-summer precipitation much below normal in the second and third years of the study. Grass standing crop (GSC) in mid July decreased with increased stocking rate, but by early October GSC was similar under the 2.5X and 3X stocking rates, but continued to be lower than that under the 2X rate. There was no consistent response in mid July forb standing crop (FSC) with respect to stocking rate. In early October, FSC was either not affected by stocking rate (1983, 1986, and 1987) or was greater under the highest stocking rate (1982, 1984, and 1985). The major changes in botanical composition and basal cover were a reduction in Indiangrass (Sorghastrum nutans Nash) and an increase in Kentucky bluegrass (Poa pratensis L.) as stocking rate increased. Botanical composition of big bluestem (Andropogon gerardii Vitman) increased under the 2X rate but did not change under the higher rates. Individual steer gains were similar under the different stocking rates, but livestock breed appeared to affect magnitude of the gain. Since individual gains did not differ, gains per ha were substantially increased by the higher stocking rates.
    • Effects of phenology, site, and rumen fill on tall larkspur consumption by cattle

      Pfister, J. A.; Manners, G. D.; Ralphs, M. H.; Hong, Z. X.; Lane, M. A. (Society for Range Management, 1988-11-01)
      Tall larkspur (Delphinium barbeyi) is a major cause of livestock death on mountain ranges. The influence of plant phenology, grazing site, and rumen fill on tall larkspur consumption was evaluated during July and August, 1987. Livestock consumption of larkspur was determined using bite counts during 4 phenological stages: bud, early flower, flower, and pod. Further, we examined larkspur ingestion in a shaded tree site and in an open sun site at 0, 50, and 100% rumen fill levels using ruminally cannulated steers. Steers on the 0, 50, and 100% fill levels consumed 9, 15, and 17% larkspur, respectively (P=0.15). There was a site effect (P=0.06) with steers eating 17 and 11% larkspur in the shade and sun sites, respectively. Over the summer, larkspur comprised 6% of cattle diets. No larkspur was consumed during the bud stage. Larkspur consumption peaked at 10% of cattle diets during the pod stage. Leaves of tall larkspur contained >3% total alkaloids (dry weight) in early July, but declined greatly with maturation. Larkspur was very nutritious, with crude protein levels 12 to 20%, and fiber levels <20% during most of the summer. Cattle diets, as determined with esophageally fistulated animals, were also high in crude protein and low in fiber during the summer. We propose a toxic window hypothesis relating larkspur palatability and toxicity. This hypothesis predicts that most cattle losses will occur during the flowering stage. We found that tall larkspur was unpalatable to cattle from the bud stage until the flowering racemes had elongated, and then consumption generally increased with plant maturation. Even though palatability and consumption increase during the grazing season, cattle can graze tall larkspur with a much lower risk of toxicosis when toxicity is low later in the grazing season.
    • Floristic changes induced by flooding on grazed and ungrazed lowland grasslands in Argentina

      Chaneton, E. J.; Facelli, J. M.; Leon, R. J. C. (Society for Range Management, 1988-11-01)
      Changes in community composition of 2 grassland sites exposed to a flood of unusual intensity and duration were investigated in the Flooding Pampa. These grasslands are subject almost annually to floodings of lesser magnitude. The study sites were adjacent to each other, and differed in vegetation structure and composition. One had been grazed continuously by cattle and was showing signs of intense deterioration. The other had remained ungrazed during 15 years. Basal cover by species was measured in summer, before and after the flooding event. Compositional difference between sites decreased with flooding from 68.9 to 39.1%. In the grazed site the cover of alien forbs was reduced by 48%. After the flooding native graminoids represented 99.7 and 86.7% of the cover, inside and outside the exclosure respectively. Total basal cover was not affected but was redistributed among species already present before the flood. Floristic changes would have led to an improvement of the forage source. We conclude that plant community response to the event was influenced by the previous grazing history of the site. The large flood acted as an overriding environmental factor which partially reverted the effects of grazing upon grassland composition.
    • Grazing effects of the bulk density in a Natraquoll of the flooding pampa of Argentina

      Taboada, M. A.; Lavado, R. S. (Society for Range Management, 1988-11-01)
      The influence of grazing by cattle on soil bulk density was studied in a typic Natraquoll of the Flooding Pampa of Argentina for a period of 33 months, by comparing a grazed situation to an enclosure deferred from grazing for 7 years. Floods took place in this period as usual. Bulk density (BD) at -33.3 kPa of water retention varied from 1.00 to 1.11 Mg m-3 in the ungrazed soil and in the grazed soil from 1.04 to 1.16 Mg m-3. Environmental factors were the primary agent controlling BD; only in some periods were there significant differences between treatments. Slight increases in BD occurred under grazing after the recession of the flood water, and significant decreases occurred in the ungrazed soil during the large and sudden falls in water content. In this case the effect of trampling, therefore, would consist mainly of impeding the decrease in BD. No compaction was observed in periods when no flood occurred or while soil remained submerged in water. The results indicated that the variations of bulk density caused by cattle trampling were superimposed on those produced by floods and showed an interaction between the effects of land-use and the particular environmental conditions of the region.
    • Stocking rate effects on intensive-early stocked Flint Hills bluestem range

      Owensby, C. E.; Cochran, R.; Smith, E. F. (Society for Range Management, 1988-11-01)