Fire severity and nutrient availability do not constrain resprouting in forest shrubs

Abstract

Plants often survive disturbances such as fire by resprouting which involves having both protection traits and carbohydrate storage capacity. Protection traits not only act directly to insulate meristems but also prevent combustion of carbohydrate stores. Rapid stem growth also allows replenishment of carbohydrate stores ensuring persistence through another event. Resource availability may, however, constrain the ability to develop resilience to high-severity fires through either nutrient limitation or light limitation. We tested whether fire severity influenced resprouting ability of woody plants in two contrasting environments, low nutrient dry sclerophyll forest and more fertile wet sclerophyll forest. We tested which fire protection and growth traits were associated with resprouting ability (27 species) and resprouting vigour (16 species). Fire severity did not limit the ability of most species to resprout in either forest type. There was no generalized protection syndrome for surviving top kill, but combinations of bud protection and growth together with storage capacity appear to drive resprouting ability. In nutrient-limited forests, low specific leaf area (SLA) may reduce stem growth in resprouters, causing more reliance on bud protection through bark thickness. Conversely, in the more fertile forests, where light becomes limiting with timesince-fire, high SLA appears to increase the capacity for rapid stem growth with less emphasis on developing thicker bark. These different syndromes appear to be adaptive as fire severity did not influence survival in either forest type.

Ecology of plant resprouting: populations to community responses in fire-prone ecosystems

“…Although it is now relatively well established that resprouter lineages do not have lower rates of molecular evolution and diversification than reseeders (Verdú et al 2007), resprouters nevertheless have the potential to dominate plant communities affected by large-scale disturbances such as fire (see in this issue: Enright et al 2011;Knox and Clarke 2011;Nano and Clarke 2011;Nzunda and Lawes 2011;Winter et al 2011). It is clear from an examination of the phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution (Crisp et al 2011;Lamont et al 2011, this issue), and the origins of fire-stimulated flowering (Lamont and Downes 2011, this issue) that resprouting has had a long history among seed plants, dating from 45 to 62 Ma.…”

“…The latter begs the question why aren't all plants resprouters? Life history differences in reproductive output and allocation between resprouters and reseeders are still emerging (this issue: Knox and Clarke 2011;Power et al 2011) but may well hold the key to explaining resprouter success. In particular, the life history differences between seedlings of typical resprouting and reseeding species deserve more attention (e.g.…”

Post‐fire regeneration in alpine heathland: Does fire severity matter?

“…Of the six measures of vegetation state assessed, the null model was most supported for all but two: shrub cover in closed heathland and bare ground in open heathland. Similarly, Knox and Clarke (2012) showed no effect of fire severity on fire-cued species in a temperate forest, and Knox and Clarke (2011) showed little long-term effect of fire severity on woody plant resprouting ability. Furthermore, ordination showed no difference between burnt and unburnt vegetation, nor was there a significant effect of fire severity on species composition in either burnt heathland community.…”

Bud protection: a key trait for species sorting in a forest–savanna mosaic

“…An unexpected result is the similarity in the number of species with underground vegetative structures and well-protected buds at low, medium and high fire frequency. These results suggest that either the potential costs of having belowground organs or buds under the bark (Vesk & Westoby, 2004;Knox & Clarke, 2011;Clarke et al, 2013;Fidelis et al, 2014) are not sufficiently high to exclude species when disturbance by fire is relaxed or absent, or bud protection and root-suckering confer competitive advantages other than resprouting after fire in fire-averse environments. Bud protection and bark growth rate are weakly correlated (0.34) for the 63 species investigated.…”