The dynamics of a Mitchell grass (Astrebla spp.) rangeland on the Barkly Tableland, Northern Territory.

The response of an area of Astrebla grassland at Helen Springs Station on the Barkly Tableland to the treatments of exclosure and distance from water were studied from 1974 to 1979. The seasonal effect produced by a number of above average rainfall years was greater than the effects of exclosure and distance from water. The total standing biomass varied from 940 kg hdl in 1974 to 2258 kg ha-' in 1979. Both Aristida latifolia and Astrebla pectinata increased in standing biomass and basal cover while the annual Iseilema vaginiflorunz decreased. Apparent responses of some species to the distance from water treatment were explained by local vegetation patterning within a seemingly uniform grassland. Regression relationships were developed that related basal cover to both species and total plant standing biomass.