Effect of season of burn on shoot recovery and post‐fire flowering performance in the resprouter Stirlingia latifolia R. Br. (Proteaceae)

Abstract

Stirlingia latifolia R. Br. is a proteaceous undershrub that is widespread in open woodlands and heathlands of the south-west botanical province of Western Australia where it is subject to frequent fires, both natural and the result of fuel-reduction burns. Shoots are completely destroyed by fire but regenerate rapidly by resprouting numerous new shoots from the root crown. Flowering is strongly triggered by fire with only sparse flowering in firefree periods. A study was undertaken to compare regrowth and flowering in populations of S. latifolia burnt in summer or autumn with populations burnt in spring as well as in unburnt population. Post-fire flowering was recorded in 92% of plants burnt in summer/autumn compared with 73% of plants burnt in spring and less than 3% in populations that had not been burnt for more than 2 years. Plants burnt in summer/autumn resprouted an average of 8.5 shoots from their root crown, of which 93% developed an inflorescence. In contrast, spring-burnt plants averaged only 5.9 shoots per plant with only 64% of these bearing an inflorescence. Ability to produce flowers was found to be related to plant age, with young individuals producing fewer or no inflorescences following spring burns in comparison with the more prolific flowering of similarly aged individuals following summer/autumn burns. Summer/autumn-burnt plants also produced significantly longer inflorescence-bearing shoots bearing a greater numbers of flower heads than those burnt in spring. Possible explanations for these results are given in the present report.

Short-term effects of burn season on flowering phenology of savanna plants

“…In contrast to our results, other studies have shown that dormant or growing-season fires increased flowering among forb and/or shrub species (Bowen and Pate 2004;GlennLewin et al 1990;Lamont et al 2000;Menges and Root 2004;Platt et al 1988;Wrobleski and Kauffman 2003). Investigations into the cause of this effect have found that increased flowering is in response to increased light levels (Norden and Kirkman 2004), physical removal of stems (McConnell and Menges 2002), nutrient pulses and increased light promoting increased flowering (Verboom et al 2002) and season of burning relative to photoperiod (Risberg and Granström 2009).…”

“…latifolia Engl., and Rosa carolina L., was negatively impacted by early-and growing-season burns. In Australia, the effect of season of burning on flowering in the resprouter, Stirlingia latifolia, was related to length of time from the burn to the production of mature shoots that could bloom, a concept that seems important for oak savanna shrub resprouters as well (Bowen and Pate 2004). (3) Flower number was reduced a year after an early-season burn compared to a previous 5-year fire (early-season shrub flowering during PP1; Table 1).…”

Fire-stimulated flowering among resprouters and geophytes in Australia and South Africa

“…This can be interpreted as a proximate response to the increase in postfire resources available for production of the more resource-demanding female cones, which ultimately has adaptive significance. In a similar way, the fraction of bisexual flowers (and thus fruits) in the andromonoecious Stirling latifolia (Ladd and Connell 1993) increases markedly in response to fire (B. Lamont, unpublished) along with the escalated flowering response (Bowen and Pate 2004).…”

“…Despite burning foliage able to reach[1,000°C in this species, the zone immediately above the apical bud remains below 60°C (Lamont et al 2004), implying that, if a heat pulse is required, the temperature reached by the apex will depend on the intensity of fire. Similarly, for the shrub, Stirlingia latifolia, 92% of plants burnt in summer/autumn flowered and 2% in winter so that Bowen and Pate (2004) suggested that the greater dry-season heat intensifies the physiological response responsible for morphogenesis. In a less seasonal climate, Gill et al (1981) recorded almost complete flowering of X. australis after spring and summer fires, but substantial flowering was delayed for 12 months after autumn and winter fires.…”

Population biology and regeneration of forbs and shrubs after fire in Brazilian Campos grasslands

“…Fire size, shape and spatial patterns affect recovering and seedling colonization of burned sites (Lavorel et al 1998). Furthermore, shoot recovery might be influenced by fire intensity and temperature (Bowen and Pate 2004).…”