Plant size and season of burn affect flowering and fruiting of the grasstree Xanthorrhoea preissii

Abstract

Flowering and fruiting were assessed on 14 populations of the grasstree, Xanthorrhoea preissii Endl., occurring in the Darling Range near Perth, Western Australia. Independent of site, season of burn or year of flowering, there was a strong relationship between plant height, which varied from 0.1 to over 2 m, and the incidence of postfire flowering, which varied from 1% (winter burn) to 75% (summer burn) of grasstrees present. There was no relationship between inflorescence dimensions, or flower or fruit production on a spike basis, and plant size/age (height). When standardized for height, spring‐burnt populations produced 40% as many inflorescences as autumn‐burnt populations and 20% as many as summer‐burnt populations. Inflorescences produced by spring‐burnt plants were moderately smaller than those by summer–autumn‐burnt plants. Fruit density per spike in autumn‐burnt plants was 80% of that in spring–summer‐burnt plants. The net effect was an average of 70 000 fruits produced per 100 summer‐burnt plants, 22 000 in autumn‐burnt plants, and 14 000 in spring‐burnt plants. Ecophysiological explanations of these results and their implications for population dynamics have yet to be explored.

Fire‐stimulated reproduction in the resprouting, non‐serotinous conifer Podocarpus drouynianus (Podocarpaceae): the impact of a changing fire regime

“…(Xanthorrhoeaceae), is also significantly influenced by fire season. Xanthorrhoea preissii produced only 40 % as many inflorescences following spring burns compared with flowering after autumn burns (Lamont et al 2000) while in X. fulva there were 20 % fewer flowering plants after a winter compared to a summer fire (Taylor et al 1998). Both S. latifolia and X. preissii co-occur with P. drouynianus, P. drouynianus might be expected to display similar seasonally-influenced seed production.…”

Post-fire flowering and fruiting in Vellozia sincorana, a caulescent rosette plant endemic to Northeast Brazil

“…Prior studies of post-fi re phenological response, with the exception of Stirlingia latifolia, an Australian species of Proteaceae (Bowen & Pate 2004), did not report the exceptionally high degree of fl owering that was observed for V. sincorana in the present study (e.g., Lamont & Downes 1979;Givnish et al 1986;Johnson et al 1994;Curtis 1998;Taylor et al 1998;Lamont et al 2000;Franceschinelli & Bawa 2005).…”

“…Other species of the same habit have been described as resistant to fi re, with the capacity to resprout their leaf rosette aft er burning, and fl ower considerably following a fi re (Lamont & Downes 1979;Givnish et al 1986;Curtis 1998;Taylor et al 1998;Mello-Silva 2004), with taller individuals fl owering more than shorter ones (Curtis 1998;Lamont et al 2000).…”

“…Several papers report the importance of fi re in the sexual reproduction of plant species in diff erent ecosystems (Coutinho 1977;Lamont & Downes 1979;Pyke 1983;Givnish et al 1986;Johnson et al 1994;Taylor et al 1998;Lamont et al 2000;Verboom et al 2002;Bowen & Pate 2004;Franceschinelli & Bawa 2005;Schmidt et al 2005;Paula & Pausas 2008). However, fi re is also viewed as an undesirable disturbance with negative impacts on the local, regional and even global environment, infl uencing climatic patterns, and sometimes precipitating changes in vegetation communities, mitigated by ecosystem type, local site characteristics, the season of year, frequency of fi re, and the amount of dry combustible material accumulated, among other factors (McNeely et al 1990;Whelan 1995;RamosNeto & Pivello 2000;Franceschinelli & Bawa 2005;Pivello 2006;Cochrane 2009).…”

Further observations on ecology of Blandfordia cunninghamii: flowering responses to rainfall and fire, and juvenile growth rates.

“…Flowering response may also be influenced by a host of environmental factors such as the burn status (whether cool, intermediate or hot), the yearly variations in temperature and rainfall, the regeneration of canopy and other vegetation layers, and access to nutrients that might enhance flowering (Lamont et al 2000;Myerscough 2009;Pyke 1983). Considerations of this nature were mostly beyond the scope of this study.…”