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Reproductive trajectories over decadal time-spans after fire for eight obligate-seeder shrub species in south-eastern Australia

Muir, Annette M., Vesk, Peter A., Hepworth, Graham
Australian journal of botany 2014 v.62 no.5 pp. 369-378
Banksia spinulosa, biodiversity, buried seeds, canopy, chronosequences, ecosystems, fires, flowering, flowers, forests, fruiting, fuels (fire ecology), life history, models, planning, reproductive performance, seed storage, sexual maturity, shrubs, Australia
Intervals between fires are critical for the persistence of obligate-seeding shrubs, and are often used in planning fires for fuel reduction and biodiversity conservation in fire-prone ecosystems worldwide. Yet information about the trajectories of reproductive performance for such species is limited and information is often qualitative. To test existing assumptions about reproductive maturity periods for eight obligate-seeding shrubs (with both canopy and soil seedbanks) in foothill forests of south-eastern Australia, we used a chronosequence approach, with sites from 2 years to >40 years post-fire. Quantitative measurements of flowering and fruiting were used to fit models of reproductive response in relation to time-since-fire for each species. Inferred reproductive maturity for each species, based on modelled times to reach 80% of maximum flower production, varied from 5 to 18 years post-fire. For a subset of three species, models predicted 80% maximum seed production occurring 1–7 years later than flowering. Our results confirmed or extended assumptions about post-fire reproductive maturity for these species, and provided a basis for improved incorporation of plant life-history in ecological fire planning. We infer that increased fire frequency makes one of our study taxa, Banksia spinulosa var. cunninghamii (Sieber ex Rchb.) A.S.George, vulnerable to decline because of its long reproductive maturity period and serotinous seed storage.