Fire regime (recency, interval and season) changes the composition of spinifex (Triodia spp.)-dominated desert dunes

Abstract

Between 2000 and 2002, central Australia experienced the largest fire season in three decades when ~500 000 km2 burned. The effects of these and preceding wildfires in the 1980s on spinifex (Triodia spp.) sand-ridge plant communities were examined at 38 sites in central Australia. We used both multivariate and univariate techniques to assess floristic differences among sites of contrasting time-since-fire, fire season and fire interval. Time-since-fire had a consistent floristic influence across the landscape, with increased abundances of ephemeral grasses and forbs and Triodia seedlings, and species richness soon after fire but decreasing long after fire. Fire season had little effect on most functional groups of plants, although seedlings of woody species were significantly more abundant following summer than winter fires. Likewise, recent short fire intervals appeared to have little impact on the population dynamics of most functional groups, although some transient effects were observed on abundances of ephemeral forbs, Triodia seedlings and herbaceous clonal species. Long-term woody species abundances appeared to be affected by short fire intervals in the 1980s when repeated fires seemed to stimulate recruitment of some resprouting species. The present study highlighted the relative stability of spinifex vegetation types in the face of landscape-scale pyric perturbation, but emphasised that localised shifts in the composition and structure of the plant community may occur under certain fire regimes.

Fire in Chihuahuan Desert grassland: Short-term effects on vegetation, small mammal populations, and faunal pedoturbation

“…and Plectrachne spp.) in Australia (Wright and Clarke, 2007), semi-arid, subtropical Australian grasslands dominated by Themeda triandra produced lower cover and biomass than unburned areas for 2.5 years post-burn. This reduced productivity occurred despite above average rainfall during the first season of recovery.…”

Fitness and evolution of resprouters in relation to fire

“…Short-interval fires, and/ or frequent pruning to simulate the effect of fire, can lead to premature death (Grano 1970;Zammit and Westoby 1987;Watson and Wardell-Johnson 2004;Wright and Clarke 2007a;Enright et al 2011). However, Wright and Clarke (2007a) report a rare instance, in central Australian spinifex-mulga vegetation, where a 2-year-interval fire resulted in an increase in resprouter abundance compared with longer intervals. Some species appear to reach a peak in their fire tolerance with young and old plants most likely to die (Burrows 1985;Hodgkinson 1998;Vesk et al 2004;Enright et al 2011).…”

“…Resprouting buffers populations against their rapid decline or even local extinction (storage effect sensu Chesson 1986) by avoiding the risk of poor recruitment following short-interval fire (Groeneveld et al 2002). Thus, resprouters should have a fitness advantage over non-sprouters in frequently burnt vegetation (Enright et al 1998a;Bellingham and Sparrow 2000;Wright and Clarke 2007a). However, resprouters are slower growing than firekilled species and can take many years to become firetolerant (Abbott 1985;van Leeuwen 1988, Enright andLamont 1992), so the fitness advantage of resprouters applies to variable fire regimes within which short fire intervals are common rather than to recurrent short intervals per se (Enright et al 1998b, Groeneveld et al 2002.…”

Harvesting as an Alternative to Burning for Managing Spinifex Grasslands in Australia

“…Fire is a natural disturbance in spinifex grasslands that recycles nutrients and maintains biodiversity and plant community structure [1,2]. Postfire native ephemeral grasses and forbs proliferate within few months but are gradually replaced by spinifex and a low cover of woody species [3,4]. While the effects of fire in spinifex grasslands are well known, it is unclear whether it is the removal of the dominant vegetation (spinifex) or the fire cues that trigger the seed germination that maintains plant biodiversity in these ecosystems.…”