Population structures of the widespread Australian conifer Callitris columellaris are a bio-indicator of continental environmental change

Prior, Lynda D.; McCaw, Lachlan; Grierson, Pauline F.; Murphy, Brett P.; Bowman, David M. J. S.

doi:10.1016/j.foreco.2011.03.030

Cited by 48 publications

(64 citation statements)

References 52 publications

(70 reference statements)

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“…The population size increases in the temperate regions may have been accelerated by relaxed herbivory following megafaunal extinctions. Although fossil evidence that extinct mammals ate Callitris is inconclusive [79], some introduced mammalian herbivores (sheep, goats and rabbits) can cause recruitment bottlenecks [31]. Our study finds no evidence of adverse effects on temperate Callitris populations, for example from putative increased burning resulting from fuel build-up following megafaunal extinction [15].…”

Section: Discussionmentioning

confidence: 47%

Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia

et al. 2013

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Climate and fire are the key environmental factors that shape the distribution and demography of plant populations in Australia. Because of limited palaeoecological records in this arid continent, however, it is unclear as to which factor impacted vegetation more strongly, and what were the roles of fire regime changes owing to human activity and megafaunal extinction (since ca 50 kya). To address these questions, we analysed historical genetic, demographic and distributional changes in a widespread conifer species complex that paradoxically grows in fire-prone regions, yet is very sensitive to fire. Genetic demographic analysis showed that the arid populations experienced strong bottlenecks, consistent with range contractions during the Last Glacial Maximum (ca 20 kya) predicted by species distribution models. In southern temperate regions, the population sizes were estimated to have been mostly stable, followed by some expansion coinciding with climate amelioration at the end of the last glacial period. By contrast, in the flammable tropical savannahs, where fire risk is the highest, demographic analysis failed to detect significant population bottlenecks. Collectively, these results suggest that the impact of climate change overwhelmed any modifications to fire regimes by Aboriginal landscape burning and megafaunal extinction, a finding that probably also applies to other fire-prone vegetation across Australia.

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Section: Discussionmentioning

confidence: 47%

Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia

et al. 2013

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“…For this work, we selected tree cores sampled during a series of studies of Callitris across Australia, building on the survey of Pearson et al (2011) and Prior et al (2011). Study sites were chosen to represent a wide range of climates across Australia, and included seven tropical, seven arid and four temperate sites ( Fig.…”

Section: Study Sites and Speciesmentioning

confidence: 99%

Continental-scale climatic drivers of growth ring variability in an Australian conifer

Bowman

Prior

Tng

et al. 2011

Trees

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Callitris is Australia's most successful and drought tolerant conifer genus. Callitris species are distributed across a huge geographical range from rainforest to arid zones, and hence they provide a rare opportunity to view plant growth trends across the continent. Here, we make a continental-scale examination of how climate influences basal diameter growth in Callitris. We sampled a total of five species but focused effort (23 of 28 samples) on the most widespread species, C. columellaris. Cores from a total of 23 trees were sampled from 15 sites that spanned a gradient in mean annual rainfall from 225 to 2117 mm and mean annual temperature from 11.5 to 28.2°C. Ring production is not annual across much of the distribution of the genus, so 14 C-AMS dating was used to establish the frequency of ring production for each core. Ring width, tracheid lumen diameter and number of tracheids per ring were also measured on each core. Ring production was close to annual at mesic sites with reliable alternation of rainfall or temperature regimes but was more erratic elsewhere. For C. columellaris, ring width significantly increased with mean annual rainfall (r 2 = 0.49) as a result of wider and more tracheids per ring. For this species tracheid lumen diameter was correlated with annual rainfall (r 2 = 0.61), with a threefold increase from the driest to the wettest sites, lending support to the hypothesis that conifers growing at drier sites will have narrow lumen diameters to maximise mechanical strength of the xylem.

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“…These include vegetation components dominated by obligate-seeder species the adult stands of which are killed by canopy scorch. Such elements of savanna vegetation in northern Australia include Callitris intratropica (Bowman et al 2001;Prior et al 2011), tropical heath communities (Russell-Smith et al 1998) and savanna woodlands dominated by Acacia spp. Fisher 1995a, 1995b).…”

Section: Introductionmentioning

confidence: 99%

Fauna and vegetation responses to fire and invasion by toxic cane toads (Rhinella marina) in an obligate seeder-dominated tropical savanna in the Kimberley, northern Australia

Radford¹,

Fairman²

2015

Wildl. Res.

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Context. Changed fire regimes are an important threatening process to savanna biodiversity. Fire-sensitive vegetation such as pindan and its fauna may be particularly susceptible to fire impacts. Invasion by alien species is an additional threatening process. The toxic anuran Rhinella marina is a well publicised invader of savannas. Little is known of impacts in many habitats.Aims. To test the hypotheses (1) that fire responses among pindan fauna are greater than general savanna responses, and (2) that cane toad-invasion impacts will be reduced relative to riparian habitats.Methods. Reptiles, frogs, invertebrates and mammals were surveyed seven times from 2008 to 2012, four times before and three times following R. marina invasion. Time since last fire was recorded during each survey. Vegetation change was measured.Key results. Pindan vegetation structural recovery took 4-5 years, whereas fauna recovery took only 1 year. Ground active agamids, combined Scincidae, fossorial skinks and ground-layer invertebrates responded positively to recent fire. Skinks of Ctenotus spp. declined in size after fire. Short-term fauna responses reflect rapid re-establishment of herbaceous cover. Fauna responses were detected following R. marina invasion, including increases in frogs of Uperoleia spp. and skinks of Carlia spp., and decreases in Lerista griffini and ground-layer invertebrates. Insufficient data were available to test for responses among large predators; however, >50% lower Varanus spp. trap success occurred post-invasion. No invasion response was detected among small mammals.Conclusions. Pindan fauna fire responses were similar to those of savannas. Fauna responses to Rhinella marina invasion were relatively minor compared with those previously reported in riparian habitats and this may be related to the lower abundance of the invader here than in previous studies in riparian or more fertile habitats.Implications. The dominant obligate seeding tree in pindan woodland, A. tumida, requires >4 years with no high-intensity fires for re-establishment of the dominant tree. Fire management should aim to minimise extensive fires to reduce impacts on fire-sensitive fauna. Persistence of large predators after cane-toad invasion suggests possible refuge value of low-productivity pindan savannas.

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Population structures of the widespread Australian conifer Callitris columellaris are a bio-indicator of continental environmental change

Cited by 48 publications

References 52 publications

Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia

Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia

Continental-scale climatic drivers of growth ring variability in an Australian conifer

Fauna and vegetation responses to fire and invasion by toxic cane toads (Rhinella marina) in an obligate seeder-dominated tropical savanna in the Kimberley, northern Australia

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