6 results on '"Shaw, Justine"'
Search Results
2. Longevity, growth and community ecology of invasive Poa annua across environmental gradients in the subantarctic.
- Author
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Williams, Laura K., Shaw, Justine D., Sindel, Brian M., Wilson, Susan C., and Kristiansen, Paul
- Subjects
ANNUAL bluegrass ,PLANT morphology ,PLANT biomass ,PLANT diversity ,INVASIVE plants - Abstract
Poa annua is a cosmopolitan weed in turf grass. It is a widespread non-native species in the subantarctic and also occurs in the Antarctic Peninsula. It has highly variable morphology, longevity and reproductive capacity across both its invaded and native range. Little is known about the ecology of P. annua in the subantarctic, particularly its longevity, morphological variation across small spatial scales and competitive ability. We monitored individual P. annua plants on subantarctic Macquarie Island to assess their longevity; quantified morphology and biomass allocation across environmental gradients; and assessed community diversity indices in areas of varying P. annua density. We show that P. annua plants on Macquarie Island are perennial, and their morphology varies with elevation, animal disturbance and soil properties. At low altitude, coastal sites with high animal disturbance and deep, sandy soils, P. annua plants are larger and native plant diversity is low. Conversely, at high altitude sites P. annua plants are smaller and the diversity of native species is not reduced. This new information informs why P. annua is the most successful plant invader in the subantarctic and quantifies some key characteristics enabling an invasive species to function well beyond its natural range. Community ecology theory can also explain patterns in the ecology of P. annua on Macquarie Island. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
3. Monitoring biological invasion across the broader Antarctic: A baseline and indicator framework.
- Author
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McGeoch, Melodie A., Shaw, Justine D., Terauds, Aleks, Lee, Jennifer E., and Chown, Steven L.
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BIOLOGICAL invasions ,BIODIVERSITY ,INFORMATION sharing ,INTRODUCED species - Abstract
Biological invasion is one of the key threats to the conservation of the broader Antarctic region. We provide an evidence-based assessment of the status of biological invasion in the region as a basis for future monitoring and management. We adapted the indicator framework for global biological invasion monitoring by collating information on (i) numbers of alien species and those invasive species impacting biodiversity (ii) trends in the extinction risks of native species impacted by invasive species and (iii) trends in relevant agreements, management intention and species eradications. Drivers of invasion including risk-associated human activities and trends were also evaluated. The number and trends in activities associated with invasion risk are broadly distributed across the region and increasing. Over 560 alien species from a wide range of taxa occupy the region, concentrated largely on the Southern Ocean Islands, with a high proportion of these considered to be invasive and to have negative biodiversity impacts. There has been a decline in the conservation status of species in the region that are impacted by invasives. Although policy responses to deal with the problem have increased since the 1970s, as have the number of successful eradications, management implementation statistics are patchy and progress in this area less apparent. The Antarctic Biological Invasions Indicator (ABII) provides a system for information exchange across the region and a vehicle for targeted monitoring and surveillance. It also enables inclusion of the region in global efforts to track both IAS and interventions for managing the threat. In a region that appears particularly prone to impacts from alien species, substantial further effort is needed to implement and monitor the effectiveness of management responses. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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- View/download PDF
4. Temporal and spatial variability in stable isotope values on seabird islands: What, where and when to sample.
- Author
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Pascoe, Penelope, Shaw, Justine, Trebilco, Rowan, Weldrick, Christine, Hindell, Mark A., and Jones, Holly
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STABLE isotopes , *STABLE isotope analysis , *NITROGEN isotopes , *SEXUAL cycle , *COLONIAL birds , *NITROGEN cycle , *NUTRIENT cycles - Abstract
[Display omitted] • Assessing ecosystem level response to invasive mammal eradication is challenging. • Nitrogen stable isotopes may provide a useful indicator of recovery on seabird islands. • Numerous confounding factors influence isotope ratios. • We show the importance of considering what, when and where sampling is undertaken. Invasive mammal eradications are widely used for managing island ecosystems. However, tracking the outcomes of such large-scale, whole ecosystem projects is challenging and costly, and monitoring all components of an ecosystem is near impossible. Instead, indicators of ecosystem change may provide more practical and integrated measures of ecosystem response to eradications. As high-order marine predators, seabirds subsidise island ecosystems with nutrients isotopically enriched in nitrogen. Invasive mammals have caused a global decline of seabirds on islands, reducing this nutrient subsidisation. Following eradications, nitrogen stable isotope analysis may provide a useful and resource-efficient indicator of ecosystem functional change on eradicated islands. However, isotope ratios are affected by a myriad of factors, with potential sources of variation being introduced by spatial and temporal variation in sampling, and within and between different taxa and ecosystem components. To correctly attribute isotopic change to post-eradication ecosystem function change, these confounding variables need to be understood. To address this need, we analysed stable isotopes of nitrogen in soil, plant, spider, and seabird guano samples collected at different distances from seabird colonies and at different stages of the short-tailed shearwater breeding cycle on six island sites around south-eastern Tasmania, Australia. Across these cool, temperate islands we detected no temporal variability in δ15N throughout the breeding season. However, there was notable spatial variability in δ15N values. The effects of seabird-derived nutrient subsidisation were highly localised with high δ15N values found inside seabird colonies and then rapidly decreasing from the colony boundary. Higher δ15N values also occurred in areas of higher burrow density within a colony. Variability in δ15N values also existed both within and between ecosystem components. Our results highlight the importance of context dependency when using ecological indicators and have important implications for the design, implementation and interpretation of studies employing stable isotopes as indicators for ecosystem change. We provide recommendations for designing future stable isotope studies on seabird islands. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. Soil properties on sub-Antarctic Macquarie Island: Fundamental indicators of ecosystem function and potential change.
- Author
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Wilson, Brian R., Wilson, Susan C., Sindel, Brian, Williams, Laura K., Hawking, Kirsten L., Shaw, Justine, Tighe, Matthew, Hua, Quan, and Kristiansen, Paul
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ENVIRONMENTAL indicators , *ISOTOPES , *ECOSYSTEMS , *ALLUVIAL plains - Abstract
Abstract We examined the nature and properties of soils on Australian sub-Antarctic Macquarie Island to determine key environmental factors driving their distribution, development and change. We provide the first classification of these soils using Australian and international (WRB) systems while combining elemental, stable and radio-isotope analysis to interpret processes of soil formation and key controlling environmental factors. Soil organic carbon (SOC) and total nitrogen (TN) concentrations across the island were influenced largely by elevation and topographic position with coastal soils and wetter depressions containing more SOC and TN compared with drier and higher elevation locations. Soils on the high, exposed plateau of the island contained low SOC and TN concentrations by comparison. Results suggested that soils of the coastal zone are subject to ongoing aggradation with significant inputs of nutrient, particularly extractable P (Ext P), from oceanic and especially avifauna sources. Nutrient subsidy was concentrated on coastal margins and the more sheltered eastern side of the island, diminishing significantly with increasing elevation and distance from the coast. Soils of the central plateau contained very low Ext P concentrations throughout the profile and appear to be relic if not degrading. Further comprehensive soil mapping, classification and monitoring across Macquarie Island will elucidate the important role that soils serve for healthy ecosystem function in these sub-Antarctic environments and provide early warning indicators of significant environmental change. Highlights • Soils are classified for the first time using Australian Soil Classification and WRB. • Soil morphology, C, N and P are determined by altitude and topographic position. • Coastal soils continue to aggrade, benefiting from oceanic/avian nutrient subsidy. • Soil 14C contents indicate that soils on the central plateau are relic or degrading. • Island soils are fundamental Indicators of ecosystem function and potential change. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
6. Human activities, propagule pressure and alien plants in the sub-Antarctic: Tests of generalities and evidence in support of management.
- Author
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le Roux, Peter C., Ramaswiela, Tshililo, Kalwij, Jesse M., Shaw, Justine D., Ryan, Peter G., Treasure, Anne M., McClelland, Gregory T.W., McGeoch, Melodie A., and Chown, Steven L.
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INTRODUCED plants , *VEGETATIVE propagation , *INVASIVE plants , *ISLAND plants , *PLANT species diversity , *VICARIANCE - Abstract
Abstract: Despite concerns about the richness of plant invaders on islands, and their likely effects on local systems, impacts of these species seem to be small. However, this may be due to an absence of information on impacts, including changing species occupancy and forecast occupancy, rather than lack of impact per se. Here we use the plant invaders on the sub-Antarctic Prince Edward Islands (PEIs) and spatially explicit modeling of presence–absence survey data to demonstrate that the geographic extent of many invasives is increasing and is forecast to lead to occupancy of >60% of the islands’ surface area by 2060, with ongoing climate change. In keeping with theory, proximity to human activity, neighboring populations (i.e. propagule pressure) and residence time, along with more minor contributors such as elevation, explain >50% of the variation in the occupancy of each of the six main invasive species on the islands. Human disturbance and changing climates seem to have led to recent increases in the rate of range expansion. Our results suggest that impacts of island plant invaders may be more significant than previously estimated, largely owing to prior data deficiency. More specifically they also suggest that control plans for the PEI (and other Southern Ocean Islands, SOIS) should first target less widely distributed species, which are invasive elsewhere. They also indicate that for the other SOIS, and for Antarctica, surveillance and anticipatory control plans should be in place. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
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