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The dramatic spatial and temporal variation in rainfall and the resource pulses which these trigger provide a challenge for predicting consumer‐primary productivity dynamics especially in arid systems. In particular, understanding is needed of the degree to which boom‐bust dynamics drive arid systems. Here, we assess the response of birds (diurnal raptors, nocturnal rodent‐specialist raptors) and rodents to a resource pulse in the western Simpson Desert across a 43‐month study period that finished in May 2011. Three rainfall pulses in rapid succession from February 2010 to March 2011 underpinned a ‘big rain’ event. Rodent populations irrupted within 6–9 months of the first of the three rainfall pulses (in February 2010). Two rodent‐specialist raptors; the letter‐winged kite, Elanus scriptus, and eastern barn owl, Tyto javanica, appeared in the area within 6–9 months of the start of the rodent irruption. By comparison with the rodents, barn owl and letter‐winged kite, diurnal raptors responded rapidly to the February 2010 rainfall event. When comparing surveys carried out the week prior to the February rainfall event with May 2010, raptor richness increased from two to six species and the index of abundance, measured as mean sightings per km, increased from 0.07 to 1.34. These findings emphasize that the 2010–2011 resource pulse was an ecologically significant event. Our results confirmed the link between big rains and rodent irruptions but they also highlighted the occurrence of finer‐scale temporal fluctuations that are less easily accounted for by rainfall patterning.

Mulga (Acacia aneura Mimosaceae) and spinifex (Triodia spp. Poaceae) habitats together characterize a large part of arid central Australia. Often very abrupt boundaries form between these two habitats, giving rise to a mosaic pattern of contrasting shrub-grass alterations across the landscape. Reasons for such patterning remain poorly understood though current niche-based views relate species' distributions to spatial resource gradients or to fire effects. Field survey work was conducted on central Australian mountain ranges to further quantify floristic, regeneration traits, and structural patterning across mulga-spinifex transitions and to test resource-and disturbance-models that explain these patterns. Compositional analysis demonstrated variability in transition type -in certain cases boundaries denoted true floristic discontinuity and in others, somewhat more of a structural shift. Moreover, it was shown that minimal between-habitat floristic overlap coincided with the occurrence of distinct edaphic changes, while greater compositional commonality occurred when soil gradients were more diffuse. This indicated that floristic patterning cannot be ascribed to any one single process. In the case of strong soil gradients, between-habitat segregation most likely resulted from resource-based niche differentiation; for weaker gradients, fire-frequency assumed greatest importance. Disturbance theory most readily accounted for the distribution of woody species' post-fire regeneration traits across habitat boundaries. The results also suggested that biotic factors -viz competition, facilitation and animal-mediated dispersal -may be of additional consequence for mulgaspinifex coexistence. Overall, the study served to emphasize the importance of multi-factor explanation for withinand between-habitat patterning in these mosaics. It also highlighted the need for experimentation to facilitate distinction between cause and correlation.

Predicting changes in vegetation structure in fire-prone arid/semi-arid systems is fraught with uncertainty because the limiting factors to coexistence between grasses and woody plants are unknown. We investigated abiotic and biotic factors influencing boundaries and habitat membership in grassland (Triodia or 'spinifex' grassland)-shrubland (Acacia aneura or 'mulga' shrubland) mosaics in semi-arid central Australia. We used a field experiment to test for the effects of: (1) topographic relief (dune/swale habitat), (2) adult neighbour removal, and (3) soil type (sand/clay) on seedling survival in three shrub and two grass species in reciprocal field plantings. Our results showed that invasion of the shrubland (swale) by neighbouring grassland species is negated by abiotic limitations but competition limits shrubland invasion of the grassland (dune). All species from both habitats had significantly reduced survival in the grassland (dune) in the presence of the dominant grass (Triodia) regardless of soil type or shade. Further, the removal of the dominant grass allowed the shrubland dominant (A. aneura) to establish outside its usual range. Seedling growth and sexual maturation of the shrubland dominant (A. aneura) was slow, implying that repeated fire creates an immaturity risk for this non-sprouter in flammable grassland. By contrast, rapid growth and seed set in the grassland shrubs (facultative sprouters) provides a solution to fire exposure prior to reproductive onset. In terms of landscape dynamics, we argue that grass competition and fire effects are important constraints on shrubland patch expansion, but that their relative importance will vary spatially throughout the landscape because of spatial and temporal rainfall variability.