Greg J. Jordan
University of Tasmania
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Publication
Featured researches published by Greg J. Jordan.
New Phytologist | 2013
Timothy J. Brodribb; Greg J. Jordan; Raymond J. Carpenter
The processes by which the functions of interdependent tissues are coordinated as lineages diversify are poorly understood. Here, we examine evolutionary coordination of vascular, epidermal and cortical leaf tissues in the anatomically, ecologically and morphologically diverse woody plant family Proteaceae. We found that, across the phylogenetic range of Proteaceae, the sizes of guard, epidermal, palisade and xylem cells were positively correlated with each other but negatively associated with vein and stomatal densities. The link between venation and stomata resulted in a highly efficient match between potential maximum water loss (determined by stomatal conductance) and the leaf vascular systems capacity to replace that water. This important linkage is likely to be driven by stomatal size, because spatial limits in the packing of stomata onto the leaf surface apparently constrain the maximum size and density of stomata. We conclude that unified evolutionary changes in cell sizes of independent tissues, possibly mediated by changes in genome size, provide a means of substantially modifying leaf function while maintaining important functional links between leaf tissues. Our data also imply the presence of alternative evolutionary strategies involving cellular miniaturization during radiation into closed forest, and cell size increase in open habitats.
PLOS ONE | 2013
David Y. P. Tng; Greg J. Jordan; David M. J. S. Bowman
Ecological theory differentiates rainforest and open vegetation in many regions as functionally divergent alternative stable states with transitional (ecotonal) vegetation between the two forming transient unstable states. This transitional vegetation is of considerable significance, not only as a test case for theories of vegetation dynamics, but also because this type of vegetation is of major economic importance, and is home to a suite of species of conservation significance, including the world’s tallest flowering plants. We therefore created predictions of patterns in plant functional traits that would test the alternative stable states model of these systems. We measured functional traits of 128 trees and shrubs across tropical and temperate rainforest – open vegetation transitions in Australia, with giant eucalypt forests situated between these vegetation types. We analysed a set of functional traits: leaf carbon isotopes, leaf area, leaf mass per area, leaf slenderness, wood density, maximum height and bark thickness, using univariate and multivariate methods. For most traits, giant eucalypt forest was similar to rainforest, while rainforest, particularly tropical rainforest, was significantly different from the open vegetation. In multivariate analyses, tropical and temperate rainforest diverged functionally, and both segregated from open vegetation. Furthermore, the giant eucalypt forests overlapped in function with their respective rainforests. The two types of giant eucalypt forests also exhibited greater overall functional similarity to each other than to any of the open vegetation types. We conclude that tropical and temperate giant eucalypt forests are ecologically and functionally convergent. The lack of clear functional differentiation from rainforest suggests that giant eucalypt forests are unstable states within the basin of attraction of rainforest. Our results have important implications for giant eucalypt forest management.
Journal of Applied Ecology | 2014
David Y. P. Tng; Steve Goosem; Greg J. Jordan; David M. J. S. Bowman
Tall old-growth forests are of global social-economic, political and ecological significance. These forests contribute significantly to the global carbon budget and are of high conservation value given sustained logging and clearing over the past two centuries (Tng et al . 2012a). In Australia, these old-growth forests extend from tropical to temperate regions of Australia in areas where rainfall exceeds 1000 mm per year, being characterized by emergent eucalypt trees attaining statures of 30 m to more than 80 m, with canopy and understorey layers consisting of mesophytic broad-leaved trees and treelets, sclerophyllous shrubs and graminoids (Fig. 1). These forests support some of the tallest flowering plants in the world, are important habitats for a unique suite of flora and fauna, and are important forest cover for metropolitan water catchments – values that make giant eucalypt forests a focal point of scientific study and ecotourism (Tng et al . 2012a). Until recently, these eucalypt forests were extensively exploited as a timber resource, but now, most remaining old-growth stands have been set aside for conservation. In some regions containing giant eucalypt forest, native forestry activities either have ceased or are based on shortrotation harvests of regrowth forests, meaning that the trees can never achieve their potential size. Regeneration typically occurs after landscape fires, and fire is also used to initiate regeneration of temperate eucalypts after logging and to reduce fuel loads (Attiwill et al ., in press). In temperate regions, fire management of the remaining stands of old-growth giant eucalypt forest is largely based upon fire suppression and fuel reduction burning in surrounding open forests, as fires in giant eucalypt forests are extremely difficult to control because these forests are only flammable under dangerous fire weather conditions (Bowman et al . 2013). In subtropical and tropical forests, fuel reduction burning is used to reduce fire hazard within the giant forests as well as in adjacent open forests and savannas. What constitutes the most appropriate and ecologically sustainable fire management practices of these giant forests remains a controversial issue among scientists, land managers and conservationists. Here, we outline recent advances in landscape ecology theory, palaeoecology and functional biology research on a giant eucalypt forest type in the Wet Tropics region of northeast Australia to explore options to achieve sustainable management of these systems. Given the ecological similarity between Australia’s giant eucalypt forests and other old-growth forests in the Northern Hemisphere (Tng et al . 2012a), the insights gleaned herein have implications for a wide range of old-growth forests. Further, the expansion of rain forest into surrounding savannas has implications for the management of savannas and grasslands, where there remains debate as to whether increased woody biomass should be managed using fire or allowed to accumulate (Bond & Parr 2010).
bioRxiv | 2018
Matthew J. Larcombe; Greg J. Jordan; David Bryant; Steven I. Higgins
Diversification processes underpin the patterns of species diversity that fascinate biologists. Two competing hypotheses disagree about the effect of competition on these processes. The bounded hypothesis suggests that species diversity is limited (bounded) by competition between species for finite niche space, while the unbounded hypothesis proposes that evolution and ecological opportunity associated with speciation, render competition unimportant. We use phylogenetically structured niche modelling, to show that processes consistent with both these diversification models have driven species accumulation in conifers. In agreement with the bounded hypothesis, niche competition constrained diversification, and in line with the unbounded hypothesis, niche evolution and partitioning promoted diversification. We then analyse niche traits to show that these diversification enhancing and inhibiting processes can occur simultaneously on different niche dimensions. Together these results suggests a new hypothesis for lineage diversification based on the multi-dimensional nature of ecological niches that accommodates both bounded and unbounded diversification processes.
Applied Vegetation Science | 2018
Stuart Macdonald; Tanya G. Bailey; Ma Hunt; Neil J. Davidson; Greg J. Jordan
Aim: To assess whether restoration of dry eucalypt-dominated plant communities on ex-pasture sites is constrained by soil characteristics. Location: Central Tasmania, Australia. Methods: We use nutrient status to test recovery trajectories of soils within eucalypt woodland restorations established on ex-pasture sites. Eucalyptus trees within these sites have been successfully established but understorey plant communities have had negligible recovery. Soils from restoration sites, aged from 3 to 22Â years, were contrasted with those from two reference ecotypes: established pastures and native eucalypt woodlands presumed to be similar to that originally replaced by the pastures. We hypothesized that (a) total soil carbon to nitrogen ratios (C:N) would be substantially higher in forest soils than in pasture soils; (b) soil nutrient levels would be lower in forest sites than within pasture sites; and (c) if restoration soils were recovering they should fit between these continuums according to age of planting. Results: Woodland and pasture reference soils were highly constrained in soil C:N and conformed to expectations. However, ex-pasture restoration sites retained the characteristically low C:N and high nutrient levels of pasture soils, in particular total N. They also failed to demonstrate a transformational effect with age of planting. Conclusions: The results suggest that both restoration interventions and natural processes had not sufficiently disrupted existing below-ground systems within the given time frame. Such an intractable stable state within the soil system highlights the need within restoration practice for an increased emphasis on soil ecological transformation. Improving and implementing practices aimed at driving soil change may assist a timelier reassembly of complex native ecosystems. This study also shows that soil C:N ratios may provide a cheap and simple means of identifying soil constraints on restoration.
American Journal of Botany | 2017
Myall Tarran; Peter G. Wilson; Michael Macphail; Greg J. Jordan; Robert S. Hill
PREMISE OF THE STUDY The capsular-fruited genus Metrosideros (Myrtaceae) is one of the most widely distributed flowering plant genera in the Pacific but is extinct in Australia today. The center of geographic origin for the genus and the reason for and timing of its extinction in Australia remain uncertain. We identify fossil Metrosideros fruits from the newly discovered Golden Fleece fossil flora in the Oligo-Miocene of Tasmania, Australia, shedding further light on these problems. METHODS Standard paleopalynological techniques were used to date the fossil-bearing sediments. Scanning electron microscopy and an auto-montage camera system were used to take high-resolution images of fossil and extant fruits taken from herbarium specimens. Fossils are identified using a nearest-living-relative approach. KEY RESULTS The fossil-bearing sediments are palynostratigraphically dated as being Proteacidites tuberculatus Zone Equivalent (ca. 33-16 Ma) in age and provide a confident Oligo-Miocene age for the macrofossils. Two new fossil species of Metrosideros are described and are here named Metrosideros dawsonii sp. nov. and Metrosideros wrightii sp. nov. CONCLUSIONS These newly described fossil species of Metrosideros provide a second record of the genus in the Cenozoic of Australia, placing them in the late Early Oligocene to late Early Miocene. It is now apparent not only that Metrosideros was present in Australia, where the genus is now extinct, but that at least several Metrosideros species were present during the Cenozoic. These fossils further strengthen the case for an Australian origin of the genus.
New Zealand Journal of Ecology | 2010
Matt S. McGlone; Sarah J. Richardson; Greg J. Jordan
Functional Ecology | 2010
David M. Wright; Greg J. Jordan; William G. Lee; Richard P. Duncan; David M. Forsyth; David A. Coomes
Forest Ecology and Management | 2001
Mike Laffan; Greg J. Jordan; Nathan Duhig
Global Ecology and Biogeography | 2014
James R. P. Worth; Grant J. Williamson; Shota Sakaguchi; Paul G. Nevill; Greg J. Jordan
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