• An Evaluation of Beta Attenuation for Estimating Aboveground Biomass in a Tallgrass Prairie

      Knapp, A. K.; Abrams, M. D.; Hulbert, L. C. (Society for Range Management, 1985-11-01)
      The attenuation of beta particles by vegetation was evaluated as a nondestructive method for estimating aboveground biomass in tallgrass prairie in northeast Kansas. Regression equations using the sum of beta attenuation measurements for each of 5 height classes within the vegetation and mean midday leaf water potential as the independent variables were used to predict live and total biomass. Live and total biomass were better predicted on burned (r2=.91 and .88, respectively) than unburned sites (r2=.71$ and .70, respectively). Greater variability in the relationship between beta attenuation and biomass in unburned prairie was a result of the large and variable amount of dead biomass on unburned sites. Dead biomass was poorly predicted by beta attenuation (r2=.24-.49). Beta attenuation predicted biomass in burned tallgrass prairie within +/- 5% of harvest values until late season vegetative senescence. In unburned prairie, predictions were poorer, but the technique could still be useful if the required accuracy need be only +/- 25%.
    • Precipitation, Soils and Herbage Production on Southeast Wyoming Range Sites

      Hart, R. H.; Samuel, M. J. (Society for Range Management, 1985-11-01)
      Herbage production and precipitation were determined at 13 locations in 483 ha of mixed grass range 1975-1979; production was determined at all locations 1982-1983, but precipitation was measured only at the main weather station. Vegetation and herbage production were more uniform on sites with similar subsoil than on sites with similar surface soil, the usual basis for site classification. Within any year, herbage production on similar sites was not correlated with spatial distribution of precipitation. Across years 1975-1979 and 1982-1983, herbage production on sites with sandy subsoil was correlated with March-April weather station precipitation (r2=0.866**) and March-April plus May-August precipitation (R2=0.95**). Herbage production on sites with loamy subsoil was not significantly correlated with precipitation in March-April (r2=0.32) or any other period.