Journal of Range Management, Volume 40, Number 5 (September 1987): Recent submissions
Now showing items 21-25 of 25
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Changes in Concentrations of Tannins, Total Phenolics, Crude Protein, and In Vitro Digestibility of Browse due to Mastication and Insalivation by CattleThe feasibility of using esophageal extrusa to monitor dietary tannin levels was studied using 4 shrub species (Purshia tridentata, Quercus gambelii, Cercocarpus montanus and Acer grandidentatum). Browse samples were hand-harvested in late summer. Half of the sample for each species was fed to esophageally fistulated cattle, while the other half served as an unmasticated control. Extrusa and control samples were analyzed for total phenolics (Folin-Denis), tannin using 3 methods (vanillin-HCl, proanthocyanidins, and astringency), crude protein, and in vitro organic matter digestibility (IVOMD). Tannin levels were reduced 10% to 60% in extrusa, depending on plant species and method of tannin analysis. Changes in the nutritional constituents of extrusa were limited but oak extrusa was higher in IVOMD than oak control samples. Tannins may have bound to plant or salivary proteins or to mucous membranes in the mouth during mastication and insalivation. Our results indicate that esophageal extrusa is not suitable for monitoring dietary tannin levels.
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Atrazine, Spring Burning, and Nitrogen for Improvement of Tallgrass PrairieSpring application of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] (1.1 kg ha-1 a.i.), burning, and nitrogen (33 kg ha-1 as ammonium nitrate) were evaluated alone and in all combinations for improvement of mid-seral tallgrass prairie in northcentral Oklahoma. Studies were initiated in 1984 (Study I) and 1985 (Study II). Precipitation and successional status of the vegetation at treatment application were higher for Study II than for Study I. Atrazine effectively reduced forbs and annual grasses for 2 years after application. Atrazine stimulated warm-season perennial grasses but did not generally increase total herbage production. Burning was similar to atrazine for annual grass control in both studies. Burning was also similar to atrazine for forb control in Study I but had no impact on forb production in Study II. Burning increased perennial grass production only in the second year of Study I. Burning decreased total herbage production in the first year of Study I by reducing annual grasses and forbs but did not affect total herbage production on other dates. Nitrogen did not consistently increase perennial grass production but did increase forb production by 250-300% when applied alone. Both atrazine and burning rapidly shifted species composition in favor of desirable perennial grasses. Nitrogen was not as effective in changing species composition either alone or in combination with atrazine and burning. The number and complexity of treatment responses declined as successional status and/or precipitation improved.
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An Evaluation of Random and Systematic Plot Placement for Estimating FrequencyA computer simulation study was conducted to evaluate the effects of pattern on the precision of frequency estimates as determined from random and systematic plot placement. Computer graphics were used to generate artificial population maps containing 40 or 80 clumps of differing spatial intensity with known frequencies of 20, 35, and 50%. The maps were repeatedly sampled both randomly and systematically using a 200-plot sample size to obtain frequency estimates. Three systematic plot spacings (4, 8, and 12) along randomly located transects were evaluated. Analysis indicated that frequency means from systematic plot placement were significantly affected by clumping, pattern intensity, and plot spacing. Random sampling resulted in frequency means that were unaffected by clumping or pattern intensity, and more consistently estimated population frequencies. An evaluation of probabilities of occurrence of Type I errors when statistically comparing frequency estimates from systematic plot placement indicated higher Type I error rates as compared to random sampling.
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A Rapid Method for Assessing Rates of Soil Erosion from Rangeland: An Example from BotswanaThe erosion of rangeland soils is a widespread problem in Africa. Yet, there are few methods for estimating its rate. Using data from 2 catchments in Botswana, a technique for estimating erosion and sediment yield is demonstrated. It involves low level photographic sampling of vegetation cover, kriging to interpolate percentage cover from sample points, and the application of a simplified soil loss estimation procedure called SLEMSA. This modelling approach gives gross soil loss and allows the estimation of sediment yield. It is easy and cheap to apply and gave results in line with field experience.
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A Model for Assessing Investments in Intensive Grazing TechnologyThe financial profitability of intensive grazing management techniques such as short duration grazing (SDG) and the Savory Grazing Management (SGM) has received very little attention in the range management or economics literature. Most research has emphasized variables which measure technical rather than economic efficiency. A conceptual economic model is presented which illustrates the importance of the management factor in determining the optimal stocking rate and profitability of cell grazing practices. Empirical results yield internal rates of return on an after-tax basis for a $10,000 grazing cell for 11-40% assuming cow herd productivity is maintained at, or increased above, pre-adoption levels. As cell costs increase and stocking rates increase, ranch profitability declines and increases respectively in almost all cases. The principal determinant of long-run profits is found to be livestock productivity since this factor has a greater impact on profitability than stocking rate levels or cell investment costs. Increased stocking rates with intensive grazing technology do not insure increased profits unless concurrent improvement in range, livestock, and business management practices are adopted.
