• Monitoring roots of grazed rangeland vegetation with the root periscope/mini-rhizotron technique

      Karl, M. G.; Doescher, P. S. (Society for Range Management, 1991-05-01)
      The root periscope/mini-rhizotron technique has been used most commonly to monitor root growth of field crops in a nondestructive manner. This study introduces a successful application of the technique for monitoring root growth of grazed rangeland vegetation. The relative, root growth response of orchardgrass (Dactylis glomerata L. 'Potomac') to defoliation by cattle was monitored on a conifer plantation in southwest Oregon. Despite stocking densities of about 2.7-4.4 animal unit/ha and 19 days of grazing during 1988, trampling and breakage of mini-rhizotrons on the cattle-grazed area was minimal. Defoliation by cattle had a negative impact on the relative number of roots for grazed orchardgrass in June and July (P < 0.05). Cautions and limitations for the use of the technique on rangelands are presented. The root periscope/mini-rhizotron appears to be a suitable, nondestructive, and affordable (1,000-1,200 per root periscope; 8.50 per mini-rhizotron) technique for monitoring root growth of rangeland vegetation defoliated by livestock and/or native ungulates.
    • Long-term effects of rangeland disking on white-tailed deer browse in south Texas

      Montemayor, E.; Fulbright, T. E.; Brothers, L. W.; Schat, B. J.; Cassels, D. (Society for Range Management, 1991-05-01)
      Brush is an important component of white-tailed deer (Odocoileus virginianus Raf.) habitat. We determined the long-term effects of offset disking on canopy cover, density, and diversity of brush species browsed by white-tailed deer. In 1989, we sampled vegetation in untreated strips and strips disked in 1973 in Jim Hogg County, Texas. Strips disked in 1974-1975 were sampled in Duval County, Texas, in 1985. Brush density was used to calculate species richness, evenness, and Shannon's index. In Jim Hogg County, Texas pricklypear (Opuntia lindheimeri Engelm.) density and canopy cover was greater in disked than in untreated strips. Density of other brush species was similar in disked and untreated strips. In Duval County, agarito (Berberis trifoliata Moric.) was the only brush species with lower density on disked (56 plants/ha) than on untreated (222 plants/ha) strips. Brush species richness and diversity were similar in the untreated and disked strips in both study areas. Landowners should consider disking for managing brush if they want to maintain brush diversity and browse for white-tailed deer.
    • Use of stochastically generated weather records with rangeland simulation models

      Wight, J. R.; Hanson, C. L. (Society for Range Management, 1991-05-01)
      We compared long-term historical and stochastically generated weather records in terms of their statistical attributes and effects on herbage yield and runoff forecasts calculated from model simulations. The historical and synthetic air temperature and solar radiation records were in good agreement in terms of monthly means and extremes. The synthetic precipitation record failed to simulate extreme precipitation events which significantly reduced forecasted runoff values. Yield forecasts were similar using either historical or synthetic weather records.
    • Technical Notes: Evaluation of dietary preference with a multiple latin square design

      Borman, M. M.; Adams, D. C.; Knapp, B. W.; Haferkamp, M. R. (Society for Range Management, 1991-05-01)
      A sequential multiple latin square experimental design was evaluated as a tool for establishing dietary preference rankings. Dietary preference of 4 grasses was determined by a series of four 4 X 4 latin squares where rows were 4 days within a pen, columns were 4 locations of a grass within a pen, and treatments were 4 grasses. Each square (i.e., pen) utilized 1 lamb. Following the completion of trial 1, the most preferred grass was withdrawn and the 3 remaining grasses were further studied with a series of four 3 X 3 latin squares. This procedure was found to be a resource efficient and effective tool for preference ranking.
    • Rangeland experiments to parameterize the water erosion prediction project model: vegetation canopy cover effects

      Simanton, J. R.; Weltz, M. A.; Larsen, H. D. (Society for Range Management, 1991-05-01)
      The Water Erosion Prediction Project (WEPP) is a new water erosion prediction technology being developed by the USDA-Agricultural Research Service to replace the Universal Soil Loss Equation. Rangeland field experiments were designed to parameterize the WEPP rangeland erosion model. Included in the field experiments were plot treatments designed to separate direct from indirect effects of vegetation canopy on runoff and soil erosion. Nine rangeland sites from a wide range of soil and vegetation types were evaluated using rainfall simulation techniques. Natural versus clipped treatment surface characteristics and runoff and erosion responses were compared using regression analyses. These analyses showed that there were no significant differences between natural and clipped plot surface characteristics, runoff ratios, final infiltration rates, or initial rainfall abstractions. Erosion rates were different between treatments with the clipped plots having slightly less erosion than the natural plots. Results indicated that, under the rainfall conditions simulated, canopy cover was not directly contributing to initial abstractions through rainfall interception loss or significantly affecting runoff or erosion.
    • Selecting Atriplex canescens for greater tolerance to competition

      Ueckert, D. N.; Petersen, J. L. (Society for Range Management, 1991-05-01)
      Success in establishing fourwing saltbush [Atriplex canescens (Pursh) Nutt.] is often limited by competition from associated vegetation. Fourwing saltbush is reported to have abundant natural genetic variation, hence selection for plant vigor or competitiveness may be an effective tool for cultivar improvement. We observed distinctive within-accession variation in the apparent ability of fourwing saltbush seedlings to tolerate competition from sideoats grama [Bouteloua curtipendula (Michx.) Torr.] in a 1982 field planting. Superior and inferior parental saltbush phenotypes in the field planting were cloned in 1984 by rooting stem cuttings, and the cloned propagules were transplanted into plots with or without competition to test the hypothesis that the competitiveness trait was genetically controlled. Survival and canopy development of superior and inferior clones planted at the same time in competition regimens were similar, suggesting that the parental phenotypes were not genetically different in their ability to tolerate competition. Differences observed in the parental phenotypes may have been environmentally induced, or genetic differences in the clonal material may have been masked by using rooted cuttings rather than seedlings, by excessive competitive pressure in the competition regimens utilized, or both. Clones from the 2 parental phenotypes performed similarly when transplanted into competition-free regimens in November when growing conditions were favorable, but canopy development of clones from superior parental phenotypes exceeded that of those from inferior parental phenotypes when transplanted into competition-free regimens in April when growing conditions were poor.