Browsing Journal of Range Management, Volume 38, Number 6 (November 1985) by Subjects
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Mechanical renovation of shortgrass prairie for increased herbage productionA study to determine the effects of single ripping, double ripping, and contour furrowing treatments was conducted on shortgrass rangeland in southeastern Wyoming from 1979-1982. The mechanical treatments changed species composition and increased total forage production over the control. Western wheatgrass (Agropyron smithii Rydb.) exhibited increased production on the treated areas compared to the control. Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] production was significantly lower on the double ripping (1981 and 1982) and the contour furrow (1981) treatments than on the control. Needle-and-thread (Stipa comata Trin. & Rupr.) exhibited an increasing trend on the single and double ripping treatment over the control treatment all 4 years. Forbs also showed his trend in 1979, 1980 and 1981 on all renovation treatments, however little difference in forb production was evident in 1982. Total production differences were the greatest in the first year of renovation (1979) and in 1980 when the annual precipitation was below the long-term average. Increased livestock carrying capacities would result in payback of the renovation costs in 4 years.
Some Growth Characteristics of Four Old World BluestemsThe growth dynamics of 4 Old World bluestem (Bothriochloa spp.) accessions were monitored in the field by periodic harvests of the aboveground biomass components (leaf blades, leaf sheaths plus enclosed stems, exerted stems plus inflorescences) during 2 growth cycles from April to September 1982. The first cycle extended from spring growth initiation (15 March) through flowering (6 July). The second cycle was initiated following the completion of the first by mowing the plants to a 50-mm stubble height and ended at flowering stage (20 September). Growth conditions during the first cycle were considered near optimum when precipitation was 1.71 of the long term mean and soil moisture averaged about 0.29 by volume. Temperatures during the second cycle were approximately 10 degrees C higher than during the first and precipitation was only 0.18 of normal. Soil moisture declined linearly throughout the second cycle and all accessions exhibited visual symptoms of drought stress. There were significant differences among accessions for most of the experimental parameters and accession ranking changed with the imposition of drought stress during the second cycle. Accessions with high relative growth rates were least tolerant of drought stress. Severe defoliation by clipping at the start of cycle 2 revealed 2 regrowth patterns which suggested potential differences in grazing tolerance. Two accessions tended to optimize canopy development by maximizing leaf area index while minimizing biomass and nitrogen investment per unit leaf area. The remaining 2 accessions produced fewer leaves with more investment per leaf. Lower relative growth rates of biomass and the ability to optimize canopy development following defoliation may result in a more stable forage source through time. Plants with these characteristics may not be top producers during periods of favorable growing conditions, but will likely maintain a level of performance under stress which compares more favorably with pre-stress performance.
Stand Age, Precipitation, and Temperature Effects on Forage YieldThe effects of seasonal distribution of precipitation on forage yield are often confounded by stand age. Forage yields of Russian wildrye (Psathyrostachys junceus), green needlegrass (Stipa viridula), crested wheatgrass (Agropyron desertorum), and intermediate-pubescent wheatgrass (Agropyron intermedium-trichophorum) were determined from 6 separate studies, each of 6 years duration, from 4 locations in the northern Great Plains. Stepwise multiple regression showed that forage yield of all 4 species was significantly (P<0.01) related with April and May precipitation and stand age. Forage yield of Russian wildrye was significantly (P<0.05) related with April mean monthly temperature and degree days (accumulation of daily mean air temperature above a given threshold temperature) accumulated until the end of May or June; however, yields of the other 3 species were not significantly related with April, May, or June mean monthly temperatures nor degree days accumulated until the end of May or June. The highest forage yield per centimeter of precipitation occurred either the second or third year after establishment; then yield decreased asymptotically and by year 5 or 6 was only 75% of maximum for green needlegrass and 40-50% for the other grasses. Economic evaluation of seeding forages must include the influence of stand age on forage yield.