An analysis of the frequency and timing of false break events in the Mediterranean region of Western Australia

Historical meteorological data were used to estimate the frequency and timing of false break events at 10 locations in the annual pasture and wheat producing area in the Mediterranean climatic region of Western Australia. The seasonal pattern of false breaks identified by this analysis was compared with the dynamics of dormancy release in a field population of subterranean clover (Trifolium subterraneum L.) to determine the influence that these events may have on the legume content of annual pasture communities in this region. False break events were estimated to occur on approximately 2 of every 3 years (61-72% of years) with no significant differences across the area investigated. Changes in the risk of false break events were examined over discrete time periods. The period of greatest risk was predicted to occur during early autumn (early March to mid April). Seed softening is virtually complete in subterranean clover at this point. The seed bank strategy of this species is, therefore, not well adapted to withstand the effects of false breaks. This might largely explain the poor persistence of subterranean clover in the annual pasture communities in the Mediterranean region of Western Australia. The legume content of these pastures might be improved by selecting species with late dormancy release strategies that will give better protection from false breaks.