Now showing items 21-23 of 23

    • Comparison of Lysimeter and Neutron Scatter Techniques for Measuring Evapotranspiration from Semiarid Rangelands

      Wight, J. R. (Society for Range Management, 1971-09-01)
      Evapotranspiration (ET) calculated from changes in soil water content measured by the neutron scatter method was compared to ET measured by lysimetry. During 1968, a near-average precipitation year (33 cm), the neutron method was effective for determining ET over periods of 4 weeks or longer. Cumulative ET curves as determined by lysimetry and the neutron method were in excellent agreement. In 1969, a year with high precipitation in June and July, reliability of the neutron method was severely limited by deep percolation and possibly by surface runoff. Failure of the neutron method to measure accurately water content near the soil surface following periods of precipitation was the major source of error when percolation and runoff were not factors. Sensitivity of the neutron method during a 30-day drying cycle was equal to that of a hydraulic lysimeter. Upward soil water fluxes were evident and are potential sources of error.
    • Changes on a Sagebrush-Grass Range in Nevada Ungrazed for 30 Years

      Robertson, J. H. (Society for Range Management, 1971-09-01)
      Thirty years rest enabled a 20-acre tract of eroded sagebrush-grass range in northern Nevada to increase its vegetal cover in all life forms. The cover of perennial forbs increased the most, 85%. Thurber needlegrass increased 7 fold. Only annual forbs and locoweed declined. Bluebunch wheatgrass was reestablishing naturally in favored spots. Newly cleared and seeded range outside the exclosure produced three times as much grass forage as produced after long rest without clearing.
    • A Portable Small-Stage Photoelectric Planimeter for Leaf Area Measurements

      Caldwell, M. M.; Moore, R. T. (Society for Range Management, 1971-09-01)
      A small and inexpensive photoelectric planimeter is described. This planimeter is particularly suited for the precise determination of leaf area for many western range species.