A method for the analysis of piosphere data applicable to range assessment.

Abstract

The logistic growth curve equation of population biology is shown to satisfactorily describe the responses of some vegetation and soil measures as a function of distance out from a watering point. Two of the three parameters of this equation can be readily related to parameters of the herbivore - rangeland ecosystem. The potential use of this equation is explored for the development of a simple, quantitative range assessment method. -

Determinants of the extent of indigenous large herbivore impact on herbaceous vegetation at watering points in the north-eastern lowveld, South Africa

“…In this study nowhere did the extent of impact on rangeland condition exceed 200 m. The effect of watering points on rangeland condition (assessed solely on herbaceous vegetation) is thus of little importance relative to that of rainfall and the stocking rate of the property. This is in contrast to the effect of watering points on livestock ranches, where larger extents of impact have been measured by Lange (1969), Foran (1980), Andrew & Lange (1986), Tolsma et al (1987), Hanan et al (1991), Perkins & Thomas (1993) and Fusco et al (1995); modelled by Graetz & Ludwig (1978), Pickup (1994) and Jeltsch et al (1997); and reviewed by Andrew (1988). A likely hypothesis for this difference is a difference in behaviour around watering points between indigenous large herbivores and livestock.…”

Long-term effects of supplementary feeding of moose on browsing impact at a landscape scale

“…Such point sources of essential resources in the landscape may create radial patterns of habitat use such as the disturbance zones (piospheres) around water sources in dry rangelands (Graetz and Ludwig, 1976;Andrew, 1988;Jeltsch et al, 1997). Central-place foraging theory, an application of the wider optimal foraging theory, describes space-use and foraging patterns by animals that frequently return to a focal place such as a den or a nest (Orians and Pearson, 1979).…”

Long-term impacts of abundant perennial water provision for game on herbaceous vegetation in a semi-arid African savanna woodland

“…A lower asymptote describes a distinct zone extending out to between 20 and 250 m from the edge of water points in which only annual, pioneer plants survive. This zone corresponds to the sacrifice area described by Graetz & Ludwig (1978). A transitional zone in which the proportion of perennial plants increases fairly rapidly with increasing distance from water lies beyond the sacrifice area.…”