Browsing by Author "Prior, LD"

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    Continental-scale climatic drivers of growth ring variability in an Australian conifer
    (Springer, 2011-10-01) Bowman, DMJS; Prior, LD; Tng, D; Hua, Q; Brodribb, TJ
    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 degrees C. Ring production is not annual across much of the distribution of the genus, so C-14-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. © 2011, Springer. The original publication is available at www.springerlink.com
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    Effect of landscape fires on the demography of the endangered New Caledonian conifer Callitris sulcata
    (Elsevier, 2015-11-01) Haverkamp, C; Prior, LD; Fogliani, B; L’Huillier, L; Anquez, M; Hua, Q; Bowman, DMJS
    New Caledonia is a global biodiversity hotspot and an epicentre for Gondwanan conifers, many of which are threatened by mining and by altered fire regimes. We studied the distribution, abundance and demography of the endangered Callitris sulcata. The largest populations are restricted to one river system in the south-east of the island, with satellite populations in adjoining rivers. The local distribution is controlled by the fire protection afforded by terrain features such as scree slopes, creeklines and small cliffs. Adult trees, which have comparatively thick bark, are able to tolerate and recover from infrequent surface fires, but severe fires kill trees and the seeds they store, a pattern similar to that in many Australian Callitris species. Radiocarbon dating revealed the species is slower growing than Australian Callitris species, possibly due to the extreme infertility of the ultramafic soils. The species is of high cultural value to the indigenous population who also prizes the durable and aromatic timber, and harvests have been traditionally regulated. Illegal cutting of trees has become a problem, but uncontrolled fires, which have caused substantial population declines, dwarf this threat. Given these threats, conservation of the species hinges on ensuring some populations remain remote and rarely visited by humans. © 2015, Elsevier Ltd.