Growth and Fire Response of Selected Epacridaceae of South-Western Australia

Abstract

Recruiting populations of seeder (Astroloma xerophyllum (DC.) Sond. and Leucopogon conostephioides DC.) and resprouter (Leucopogon verticillatus R.Br. and Conostephium pendulum. Benth.) epacrids were examined over an 8 year period, using time of fire, shoot morphology and root xylem ring number to age plants. The seeders commenced flowering earlier, achieved three-fold higher shoot:root ratios but accumulated much smaller root starch reserves than the resprouters. The resprouting potential of L. verticillatus was 'bud initiation-limited', since progressive shoot removal exhausted the bud-producing potential but did not fully deplete the starch reserves of the root stock. Apparent conversion efficiency of starch to new shoot biomass was 88%. The corresponding response in C. pendulum was 'energy reserve-limited', with shoot removal eliminating root starch but leaving many unexpanded buds. Dendroecological analyses of root xylem growth rings were undertaken on 15 year-old plants of C. pendulum recruiting from seed in unburnt and adjacent periodically burnt habitats. Growth ring extension of burnt plants resumed after each fire at rates faster than their unburnt counterparts, suggesting that improved access by resprouting shoots to light, water and nutrients compensated for destruction of the previous shoot system.