Effects of multiple fires on tree invasion in montane grasslands

Fairfax, R. J.; Fensham, R. J.; Butler, Don; Quinn, Kelvin; Sigley, Bernice; Holman, J. E.

doi:10.1007/s10980-009-9388-y

Cited by 36 publications

(36 citation statements)

References 65 publications

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“…Conversely, with more than 30 years of fire exclusion there was no evidence that the sclerophyllous communities became more floristically similar to rainforest. These short-term floristic patterns contrast with longer-term remote sensing that show rainforest expansion into sclerophyllous vegetation elsewhere in Australian with fire exclusion (Russell-Smith et al, 2004;Fairfax et al, 2009).…”

Section: Floristic and Pyrogenic Trait Shiftscontrasting

confidence: 64%

“…Fire-driven forest community boundary changes are well documented (Ash, 1988;Banfai and Bowman, 2006;Banfai et al, 2007;Fairfax et al, 2009) but evidence for large-scale pyrogenic conversion of one state to another, driven by positive feedbacks, has been too reliant on assumptions of plant mortality, trait shifts and feedbacks. We have shown the need to validate these assumptions because, whilst fire feedbacks were detected, species assemblages in rainforest were resilient to a high severity fire event.…”

Section: Resultsmentioning

confidence: 99%

“…These results challenge the notion that Australian rainforest species are highly fire sensitive because an increasing number of studies are showing that rainforest species persist through respouting after intense fire (Williams, 2000;Marrinan et al, 2005;Clarke et al, 2009). Repeated fires are therefore invoked as a mechanism for decline as has been demonstrated in forests species in savannas (Bowman, 2000;Hoffmann et al, 2009) but there is little evidence that fire frequencies at 20-50 year intervals, even at rainforest edges, would be sufficient to cause extirpation of forest species (Bowman, 2000;Williams, 2000;Fairfax et al, 2009;Hoffmann et al, 2009). The fundamental assumption that fire regimes maintain alternative stable states in rainforest because canopy dominants are fire-killed (Ash, 1988;Geldenhuys, 1994) needs to be re-examined because these forests are more resilient to individual fires, including high severity fires, than previously assumed.…”

Section: Floristic and Pyrogenic Trait Shiftsmentioning

confidence: 99%

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Fire severity, feedback effects and resilience to alternative community states in forest assemblages

Knox

Clarke

2012

Forest Ecology and Management

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Section: Floristic and Pyrogenic Trait Shiftscontrasting

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Section: Floristic and Pyrogenic Trait Shiftsmentioning

confidence: 99%

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Fire severity, feedback effects and resilience to alternative community states in forest assemblages

Knox

Clarke

2012

Forest Ecology and Management

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“…Other possible explanations for the absence of trees in upland grasslands have included thermal constraints on growth or survival (e.g. frost damage; Acocks 1953), fire (Bragg and Hulbert 1976;Fairfax et al 2009), fire and grazing (Mark 1958;Knapp et al 1999), climate (Weaver 1954Webb 1964), grass competition (Walter 1979), and seed dispersal (Fensham and Fairfax 2006). Despite similar biogeographical patterns around the globe, there is as yet no conceptual framework or general explanation for the tree-less nature of upland C 4 grasslands.…”

Section: Variablementioning

confidence: 99%

Is the lack of leguminous savanna trees in grasslands of South Africa related to nutritional constraints?

2010

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As with many grasslands globally, the Highveld grasslands of South Africa are tree-less, despite having a climate that can support tree growth. Models predict that fire maintains these grasslands. The question arises as to why fire-tolerant savanna trees do not survive in these ecosystems? Savanna tree survival in mesic areas is restricted by demographic bottlenecks, specifically limitations to sapling-escape from fire. It was hypothesised that ancient highly leached soils from grassland areas would prevent saplings from growing fast enough to escape the fire-trap. Growth rates of savanna tree seedlings (Acacia karroo Hayne and Acacia sieberiana Burtt Davy) were measured in a common garden experiment using soils from ten sites collected along a savanna-grassland continuum. Soils from grassland sites were relatively nutrient-poor compared to those from savannas with lower pH, and associated cations. A. sieberiana growth rates responded to pH and these nutrients, whereas A. karroo growth was less strongly linked to specific nutrients. Even so, both species accumulated more biomass when grown in soils from savanna sites compared to grassland sites. An exception was a low elevation low nutrient savanna site that resulted in poor growth, yet sustains high tree biomass in situ. Differences between growth in grassland and savanna soils were small. They may contribute to, but are unlikely to explain, the treeless nature of these grasslands.

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“…Fire limits the distribution of tree species in montane grasslands and its widespread withdrawal during the 20th century has caused overwhelming woody expansion (Geldenhuys 1994;Coop and Givnish 2007;Fairfax et al 2009). In South Africa, temperate grasslands retain heathland elements but only at high altitude (1800-2800 m a.s.l) where fire has been excluded for decades (Carbutt and Edwards 2001).…”

Section: Introductionmentioning

confidence: 99%

The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sprouting tree Protea caffra in temperate grasslands

Adie

Richert²,

Kirkman

et al. 2011

Plant Ecol

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We examined the effect of fire frequency and intensity on a Protea caffra tree population in the temperate montane grasslands of north-western KwaZulu-Natal, South Africa. We assessed the effect of fire by comparing the population structure of the resprouter P. caffra in discrete bracken (Pteridium aquilinum) patches with that in the surrounding grassland matrix. Fuel biomass did not differ between grassland and bracken, but bracken fuel was significantly drier than grass. Above-ground fire temperatures and fireline intensity, measured by P. caffra char height, were significantly higher in the bracken habitat. Forty-two percent of the P. caffra population in grassland and in bracken persisted by coppice resprouts, having lost their original stem to fire damage. Exposure to higher intensity bracken fire suppressed P. caffra regeneration and caused greater adult mortality compared with trees in grassland. Consequently, the P. caffra population in bracken was skewed towards old age with most trees severely fire damaged. The high incidence of small trees in grassland indicates that a regular fire interval of 2-3 years does not negatively affect regeneration of P. caffra. However, in bracken patches regular high intensity fires cause high mortality among all P. caffra size classes and will ultimately result in local extinction. Bracken thus has the potential to significantly alter tree-grass interactions in these montane grasslands.

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Effects of multiple fires on tree invasion in montane grasslands

Cited by 36 publications

References 65 publications

Fire severity, feedback effects and resilience to alternative community states in forest assemblages

Fire severity, feedback effects and resilience to alternative community states in forest assemblages

Is the lack of leguminous savanna trees in grasslands of South Africa related to nutritional constraints?

The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sprouting tree Protea caffra in temperate grasslands

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