The effects of parent density and season of burn on the regeneration of Leucadendron laureolum (Proteaceae) in the Kogelberg

Applied Vegetation Science

Wilgen³

et al. 2012

Question: Fire management practices aimed at biodiversity conservation are often in conflict with hazard reduction requirements. Particularly in protected areas where such conflict of interest exists, the question is asked: what are the ecological thresholds within which fire should be managed? Location: Montane proteoid fynbos shrublands, eastern coastal part of the Cape Floral Kingdom; coastal slopes of the Tsitsikamma and Outeniqua Mountains, South Africa.Methods: Estimates of optimal fire frequencies are often based on the relationship between plant age and the rate of seed accumulation of the slowest-maturing species. We established juvenile periods and recruitment success (measured as the ratio of post-fire recruits to the pre-burn population) after fires at different intervals, of serotinous, reseeding shrubs in the Proteaceae. From this we estimated minimum fire return intervals (FRIs) that would allow for their persistence in eastern coastal fynbos shrublands.Conclusions: From an ecological perspective, our findings imply a minimum FRI of 9 yr for eastern coastal fynbos. This is not intended to prescribe rigid management of fire according to a fixed rotation and does not negate the need to consider site-or species-specific requirements. Instead it provides a lower threshold for a range of acceptable FRIs below which a significant decline of species populations is predicted.

Section: Discussionmentioning

confidence: 99%

“…Season of burn, age of the vegetation at the time of surveying, and pre‐fire parent density (Bond ; Bond et al. ; Le Maitre ,b; Heelemann et al. ) may additionally affect recruitment success.…”

Section: Methodsmentioning

confidence: 99%

Proteaceae juvenile periods and post‐fire recruitment as indicators of minimum fire return interval in eastern coastal fynbos

Kraaij

Applied Vegetation Science

Wilgen³

et al. 2012

“…Fourcade is a dioecious, serotinous shrub up to 2 m tall, which is common in low altitude fynbos communities in the southwestern Cape (Taylor 1969;Le Maitre 1988;Cowling & Gxaba 1990). It often occurs in dense stands, and is the dominant overstorey proteoid in the areas where banksias are currently cultivated.…”

Section: Study Speciesmentioning

confidence: 99%

The invasive potential of Australian banksias in South African fynbos: A comparison of the reproductive potential ofBanksia ericifoliaandLeucadendron laureolum

Honig

Australian Journal of Ecology

Richardson³

1992

906

Several taxa of the Australian Proteaceae have invaded South African fynbos and require costly management programmes to bring under control. Banksia spp. have been introduced only recently to fynbos regions. The invasive potential of Banksia ericifolta (Proteaceae) was investigated by comparing its recruitment potential with that of an indigenous proteaceous shrub, Leucadendron laureolum. Both species are overstorey shrubs that are killed by fire and rely on canopy-stored seeds (serotiny) for recruitment. Eight year old B. ericifolia shrubs produced an average of 16 500 seeds per plant, which is thirty times more than the average of 570 seeds produced by 10 year old L. laureolum shrubs. The seed bank of fi. ericifolia was not only larger than that of L. laureolum (1098 w 525 viable seeds m ~ -projected canopy cover), but also considerably larger than that described for the species in its native environment (200-330 seeds m^^ina9year old stand north of Sydney). Leucadendron lau reoleu m released most of its seed a few days after the cones were burnt, whereas seed release in B. ericifolia was spread over 12 weeks. The seeds of B. ericifolia had lower wingloading and fall rates than L. laureolum and were dispersed over greater distances. The relative seedling growth rates of the two species were very similar (0.03 g per day), but below-ground biomass was greater and proteoid roots were more developed in B. ericifolia seedlings than in L. laureolum after 100 days. Four year old B. ericifolia plants growing in the field had attained over twice the height of indigenous proteoids and accumulated up to 10 times the fresh biomass of L. xanthoconus, a species which is ecologically similar to L. laureolum. The Bioclimatic Prediction System (BIOCLIM) was used to create a bioclimatic profile of B. ericifolia and identify climatically suitable areas in the Cape Province. Results show that its potential distribution covers most fynbos areas in the southwestern Cape. It is concluded that B. ertcifolia has the potential to be highly invasive in fynbos.

“…In particular, when a species in a community becomes rarer than a competitor, persistence is ensured by a higher relative per capita growth rate. There is evidence for density-dependent reproductive output in fynbos proteoid shrubs: shrub size, seed production and post-fire seedling to parent ratios decline with increasing density (Bond et al 1984;Le Maitre 1988;Esler & Cowling 1990). There are fewer data showing very high per capita population growth of rare species.…”

Section: Evidence and Tests For Lottery Coexistence In Fynbos And Kwomentioning

confidence: 99%

Lottery coexistence models extended to plants with disjoint generations

Laurie

1995

J Vegetation Science

Abstract. Neither conventional niche theory nor current lottery models offer a satisfactory theoretical scope for modelling coexistence of species with disjoint generations. South‐African fynbos and Australian kwongan include many species which are killed by, and recruit only after, fire. We propose a density‐dependent lottery model which accommodates the unusual demographics of these species. We show that coexistence requires density dependence in recruitment. The result applies to a wider class of populations than the one considered here. It is applied to non‐resprouting species in fynbos and kwongan. We show that the lottery assumption of recruitment in proportion to propagules is often satisfied, while the production of such propagules is often density‐dependent, and we discuss some evidence of mechanisms whereby this may occur.