https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30180 2 drawdown during the last glacial period were linked to iron (Fe) fertilization of subantarctic surface waters. The principal source of this Fe is thought to be dust transported from southern mid-latitude deserts. However, uncertainty exists over contributions to CO₂ sequestration from complementary Fe sources, such as the Antarctic ice sheet, due to the difficulty of locating and interrogating suitable archives that have the potential to preserve such information. Here we present petrographic, geochemical and microbial DNA evidence preserved in precisely dated subglacial calcites from close to the East Antarctic Ice-Sheet margin, which together suggest that volcanically-induced drainage of Fe-rich waters during the Last Glacial Maximum could have reached the Southern Ocean. Our results support a significant contribution of Antarctic volcanism to subglacial transport and delivery of nutrients with implications on ocean productivity at peak glacial conditions.]]> Wed 11 Apr 2018 17:19:42 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:48873 Thu 13 Apr 2023 12:40:33 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19826 Sat 24 Mar 2018 07:56:55 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30556 Athrotaxis cupressoides D. Don (461 samples from 20 populations) and Diselma archeri Hook.f. (576 samples from 23 populations, 16 of which were for sites sampled for A. cupressoides), were genotyped using eight and nine EST nuclear microsatellites respectively. Genetic diversity and structure was compared between the two species and the factors underlying genetic patterns in both species were investigated by examining isolation by distance, correlations with Last Glacial Maximum modelled distributions and the fossil record, and a fire history index of the sampled stands. Results: The range-wide genetic structure of the two species was similar (F_st = 0.09 and F’_st = 0.21 for A. cupressoides versus D. archeri; F_st = 0.06 and F’_st = 0.24), and there were significant correlations between species for population-based expected heterozygosity, allelic richness, private allelic richness and pairwise genetic divergences. Furthermore, genetic diversity metrics decreased significantly with an index of fire history. Given fossil evidence and modelling evidence that both species occurred near their current ranges during the last glaciation and a lack of evidence for isolation by distance in either species, the plausible explanation for the patterns of diversity is genetic decline resulting from repeated Holocene fires. Main conclusions: Our study suggests that fire can have substantial impacts on genetic structure and diversity of plant species, particularly those without fire-tolerant traits, and that any increases in fire resulting from climate change may impose substantial threats to such species. In Tasmania, the observed increase in dry lightning in recent years, combined with periods of abnormally dry conditions, may therefore further degrade the range and genetic diversity of fire-intolerant palaeoendemic species.]]> Sat 24 Mar 2018 07:27:09 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3429 Sat 24 Mar 2018 07:20:25 AEDT ]]>