Using a rainforest-flame forest mosaic to test the hypothesis that leaf and litter fuel flammability is under natural selection

• Published in: Oecologia 2014-12, Vol.176 (4), p.1123-1133
• Main Authors: Clarke, Peter J, Prior, Lynda D, French, Ben J, Vincent, Ben, Knox, Kirsten J. E, Bowman, David M. J. S
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Australia; Biological and medical sciences; Biomedical and Life Sciences; bulk density; Climate; Ecology; Ecosystem; ECOSYSTEM ECOLOGY; Ecosystem ecology - Original research; Eucalyptus; Fire ecology; fire hazard; Fire hazards; Fire severity; Fires; Flammability; Foliage; Forest canopy; Forest fires; Forest litter; Forest regeneration; Forestry; Forests; Fuels; Fundamental and applied biological sciences. Psychology; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Habitats; Hydrology/Water Resources; Leaves; Life Sciences; Litter; Microclimate; Moisture content; natural selection; Plant Leaves; Plant Sciences; Plants; Rain forests; Rainforest; Rainforests; recruitment; Selection, Genetic; Sustainability; temperate forests; Temperate rain forests; Trees; water content
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-014-3071-y

We used a mosaic of infrequently burnt temperate rainforest and adjacent, frequently burnt eucalypt forests in temperate eastern Australia to test whether: (1) there were differences in flammability of fresh and dried foliage amongst congeners from contrasting habitats, (2) habitat flammability was related to regeneration strategy, (3) litter fuels were more flammable in frequently burnt forests, (4) the severity of a recent fire influenced the flammability of litter (as this would suggest fire feedbacks), and (5) microclimate contributed to differences in fire hazard amongst habitats. Leaf-level comparisons were made among 11 congeneric pairs from rainforest and eucalypt forests. Leaf-level ignitability, combustibility and sustainability were not consistently higher for taxa from frequently burnt eucalypt forests, nor were they higher for species with fire-driven recruitment. The bulk density of litter-bed fuels strongly influenced flammability, but eucalypt forest litter was not less dense than rainforest litter. Ignitability, combustibility and flame sustainability of community surface fuels (litter) were compared using fuel arrays with standardized fuel mass and moisture content. Forests previously burned at high fire severity did not have consistently higher litter flammability than those burned at lower severity or long unburned. Thus, contrary to the Mutch hypothesis, there was no evidence of higher flammability of litter fuels or leaves from frequently burnt eucalypt forests compared with infrequently burnt rainforests. We suggest the manifest pyrogenicity of eucalypt forests is not due to natural selection for more flammable foliage, but better explained by differences in crown openness and associated microclimatic differences.