Time‐since‐fire and climate interact to affect the structural recovery of an Australian semi‐arid plant community

Abstract

How does time-since-fire influence the structural recovery of semi-arid, eucalypt-dominated Murray-Mallee shrublands after fire, and is recovery affected by spatial variation in climate? We assessed the structure and dynamics of a hummock grass, Triodia scariosa N.T. Burb, and mallee eucalyptstwo key structural components of mallee shrublandsusing a >100 year time-since-fire chronosequence. The relative influence of climatic variables, both individually and combined with time-since-fire, was modelled to account for spatial variation in the recovery of vegetation structural components. Time-since-fire was the primary determinant of the structural recovery of T. scariosa and eucalypts. However, climate, notably mean annual rainfall and rainfall variability, also influenced the recovery of the eucalypt overstorey, T. scariosa cover and mean hummock height. We observed that (i) the mean number of live eucalypt stems per individual decreased while mean individual basal area increased, (ii) cover of T. scariosa peaked at~30 years post-fire and gradually decreased thereafter, and (iii) the 'hummock' form of T. scariosa occurred throughout the chronosequence, whereas the 'ring' form tended not to occur until~30 years post-fire. Time-since-fire was the key determinant of the structural recovery of eucalyptdominated mallee shrublands, but there is geographical variation in recovery related to rainfall and its variability. Fire regimes are likely to have different effects across the geographic range of mallee shrublands.Estimated degrees of freedom (edf = 1.00 represents a linear relationship). Vegetation types are CM: Chenopod Mallee and TM: Triodia Mallee. 'Rainfall var.' is annual rainfall variability, 'rainfall' is mean annual rainfall and 'evaporation' is mean annual evaporation. All models within two AIC of the best model are shown where there were models within two AIC.

Modeling variability in the fire response of an endangered bird to improve fire‐management

“…Elevation and gypsum content did not change across a broad geographic gradient, as changes in other environmental variables often do (e.g., mean annual rainfall; Barry and Elith 2006, Puig-Giron es et al 2017, Kenny et al 2018). Furthermore, variability in the Mallee Emu-wren fire response was not associated with differences in vegetation type, as other authors have found (Gosper et al 2012, 2013, Janion-Scheepers et al 2016.…”

“…, Kenny et al. ). Furthermore, variability in the Mallee Emu‐wren fire response was not associated with differences in vegetation type, as other authors have found (Gosper et al.…”

“…, Kenny et al. ). Candidate models included environmental variables as additive terms, as two‐way interactions with time since fire and as two‐way interactions with time since fire plus additive terms.…”

“…As a result, extent cover of Tall Triodia cover is a focus of this study. Tall Triodia is reported to reach a maximum extent of cover at~35 yr since fire, after which extent of cover declines , Kenny et al 2018.…”

“…We used the second-order polynomial form of time since fire in all analyses. This is because many studies over the last decade have identified a unimodal response to time since fire for Mallee Emu-wren occurrence and extent cover of Triodia (Brown et al 2009, Connell et al 2017, Kenny et al 2018. Candidate models included environmental variables as additive terms, as two-way interactions with time since fire and as two-way interactions with time since fire plus additive terms.…”