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Fire persistence traits can be used to predict vegetation response to changing fire regimes at expansive landscape scales – an Australian example

Authors


Jeremy Russell-Smith, Bushfires NT, PO Box 37346, Winnellie, NA 0821, Australia.
E-mail: jeremy.russell-smith@nt.gov.au

Abstract

Aim  Building on a substantial literature addressing the fire responses of woody plants, particularly under mediterranean climates, we assess the extent to which fire persistence traits can be used to predict vegetation responses to fire regime changes in fire-prone arid and savanna landscape settings.

Location  Australia, applying data from arid central to monsoonal northern regions (11–26° S, 129–138° E).

Methods  With reference to a substantial sub-continental floristics dataset, we first assigned the fire response (obligate seeder, resprouter) and seedbank persistence (transient, dormant) of rapid and longer-maturing (> 3 years) woody taxa. Using logistic regression, we then modelled the proportions of taxa possessing these traits as a function of mean annual rainfall (highly correlated with fire frequency) and terrain roughness (a measure of topographic variability) in 0.25° × 0.25° and 1° × 1° grid cells. Separate assessments were undertaken with datasets for 1264 sclerophyll and 236 rain forest taxa.

Results  This woody flora is characterized by taxa exhibiting mostly resprouting and dormant seedbank traits that promote site persistence. While numbers of obligate seeder and resprouter taxa were related positively to both rainfall and roughness, the relative abundance of both sclerophyll and rain forest obligate seeders decreased significantly with rainfall. The relative abundance of sclerophyll (especially long-lived) obligate seeders alone increased with topographic roughness. The proportion of taxa with transient seedbanks increased with rainfall in resprouters generally, and in rain forest obligate seeders alone.

Main conclusions  We find that resprouters are favoured on more productive, fire-prone sites, and obligate seeders are favoured in less productive, more fire-protected settings. Seedbank persistence responses are more variable. These findings concur generally with theoretical constructs, and support comparable assessments in Australian and other fire-prone systems ranging from mediterranean to boreal environments. Our observations illustrate that resprouting and obligate seeding syndromes, but not necessarily seedbank persistence, are useful predictors of vegetation responses to changing fire regime conditions at large landscape scales.

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