The Population Dynamics of Perennial Shrubs in a Western Australian Chenopod Shrubland in Relation to Grazing and Seasonal Conditions.

Abstract

This paper examines the responses of a chenopod community in arid Western Australia to various grazing treatments over an eight-year period. The population dynamics of the major perennial species are analysed in relation to grazing treatments and seasonal conditions. Continuous grazing and spelling had no discernible impact on community composition when compared with the nil- grazing treatment. However, continuous grazing increased population turn-over rate, which reflected a higher level of recruitment and mortality, when compared with the nil-grazing treatment. In general, populations of all major perennial species remained stable or increased during the study period. Both mortality and recruitment were sporadic, corresponding to the erratic rainfall events during the trial period. For the three major perennial species, Maireana georgei, M. pyramidata, and Ptilotus beardii, linear regression analyses reveal that 38-74% of the variation in mortality and recruitment was caused by seasonal conditions.