Fire may stimulate flowering, branching, seed production and seedling establishment in two kangaroo paws (Haemodoraceae)

Published source details Lamont B.B. & Runciman H.V. (1993) Fire may stimulate flowering, branching, seed production and seedling establishment in two kangaroo paws (Haemodoraceae). Journal of Applied Ecology, 30, 256-264.
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Summary

The flowers of two species of kangaroo paws, Macropidia fuliginosa and Anigozanthos pulcherrimus (Haemodoraceae), part of the sclerophyllous flora in Mediterranean-type scrublands in Western Australia, are greatly sought after in the wildflower trade because of their attractive inflorescences. Although locally common, concern had been raised over the long-term effect of commercial picking. This study looked at the fire responses of these species in order to make management recommendations for conservation, tourism and commercial wildflower picking.

Study site: Six populations of Macropidia fuliginosa and four of Anigozanthos pulcherrimus in a 52 x 20 km² area near Badgingarra, 200 km north of the city of Perth (30º15'S, 115º15'E), in Western Australia.

Monitoring: Two of the sites for each species could be divided into recently burnt (<2 years) and not recently burnt (9-19 years previously) areas. Populations were aged, and the various populations were assessed over 1-3 years (1986-1988).

M.fuliginosa populations were of low density so entire populations (covering 956-2,934 m²) could be sampled. A.pulcherrimus populations were large and dense therefore four or five randomly placed 5 x 5 m² quadrats per population were sampled. Cilms were inspected at peak flowering, and flowering and vegetative condition recorded. The results were collated to give the proportion of culms flowering per stand.

At the start of winter (May-June) 1986, the following treatments were randomly applied to each of 10 A.pulcherrimus clumps (4-11 culm clusters): burning, fertilizing and ash application (to simulate nutrient release after fire); clearing and raking (to simulate removal after fire); clipping of foliage, soil heating; and an untreated control.

Branching, seed production and seedling establishment were monitored between1986 and 1987.

Flowering (number of panicles) in the both kangaroo paw species was greatest the year following fire, declining sharply to negligible levels after 5 years: M.fuliginosa flowering varied from 34% of culms in year 1 after fire, to 0% in years 13, 17 and 18; A.pulcherrimus flowering varied from 69% of culms in year 1, to 0% in years 9, 10 and 13.

The flowering response of A.pulcherrimus was simulated in the absence of fire by applying fertilizer (14.3% of culms in flower in 1986) and to a lesser extent by removing litter (5.6%) or foliage clipping (8.9%) compared to controls (4.7%). In comparison, burnt clumps had 10.9% of culms in flower in 1986.

Seed production per panicle remained constant or increased over two successive years after fire; but seed production per unit area declined.

Flowering culms, even when their panicles were removed, usually produced two axillary culms the next season, while vegetative culms retained their apical dominance.

Seedling establishment in M.fuliginosa was most likely during the first year after fire, attributable to enhanced germination of seeds in the seed bank. Despite producing one to two orders of magnitude more viable seeds per unit area than M.fuliginosa, seedling establishment by A.pulcherrimus was insignificant.

Conclusions: Fire and other management practices (e.g. judicious use of fertilizers) could be used to manipulate flowering of these two kangaroo paw species for the benefit of commercial flower picking and ecotourism but the population viability of other, less fire-tolerant, species might be threatened.

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