DYNAMICS OF PERENNIAL PLANTS IN THE MULGA (ACACIA ANEURA F. MUELL.) ZONE OF WESTERN AUSTRALIA 11. SURVIVAL OF PERENNIAL SHRUBS AND GRASSES

Abstract

Survival rates of arid-land perennial plant species were significantly related to climate, site factors, and grazing by kangaroos (Macropus rufus, Desmarest and Macropus robustus, Gould). Rainfall patterns ranging from severe drought to well above average resulted in responses in all species. All but Frankenia (Frankeniapauciflora, DC) responded to spatial and temporal site factors. Survival of wire wanderrie grass (Eragrostis xerophila, Domin) was severely reduced by grazing kangaroos, while poverty bush (Eremophila spectabilis, C.A. Gardn.) and Frankenra responded positively to kangaroo activity. Cotton bush (Ptilotus obovatus, Gaud.), ball-leaf bluebush (Marreana glomerifolia), (F. MueH et Tate) Wils. and Wilcox bush (Eremophila leucophylla, Benth.) showed no survival response to kangaroo grazing. The application of maximum likelihood procedures permitted subtle effects to be detected and several significant causal factors to be separated.