The following 14 out of 15 criteria
|1.||Serve as a robust indicator of environmental change|
|2.||Reflect a fundamental or highly-valued aspect of the environment or an important environmental issue|
|3.||Be either national in scope or applicable to regional environmental issues of national significance|
|4.||Provide an early warning of potential problems|
|5.||Be capable of being monitored to provide statistically verifiable and reproducible data that shows trends over time and, preferably, apply to a broad range of environmental regions|
|6.||Be scientifically credible|
|7.||Be easy to understand|
|8.||Be monitored with relative ease|
|10.||Have relevance to policy and management needs|
|11.||Contribute to monitoring of progress towards implementing commitments in nationally important environmental policies|
|12.||Where possible and appropriate, facilitate community involvement|
|13.||Contribute to the fulfillment of reporting obligations under international agreements|
|15.||Where possible and appropriate, be consistent and comparable with other countries� and state and territory indicators|
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Quantification of bryophyte community dynamics along the transects measured, showed that the three Windmill Islands moss species, Bryum pseudotriquetrum, Grimmia antarctici, and Ceratodon purpureus, and the liverwort, Cephaloziella exiliflora, have differences in their relative distributions. Grimmia antarctici and B. pseudotriquetrum, the two most abundant species, show opposite abundance trends along the transects: G. antarctici increases in abundance with increasing distance along the transects, while B. pseudotriquetrum decreases. Ceratodon purpureus, and the liverwort, C. exiliflora, present at lower levels of abundance, respond in the same direction as B. pseudotriquetrum, decreasing in abundance with increasing distance along the transects.
These relative species distribution patterns have significant implications for the quantification of Windmill Islands community dynamics in response to climate change. With respect to the Windmill Islands three moss species, research shows that the physiological tolerance of desiccation is greatest in C. purpureus and lowest in the Antarctic endemic, G. antarctici (Robinson, Wasley et al. 2000). The relative species distribution patterns we have found support these physiological responses: C. purpureus is most abundant in higher, drier, areas, while G. antarctici is highest in abundance in lower, wetter, areas. The status of future water availability in the Windmill Islands is unclear. Currently the Windmill Islands are undergoing a drying trend, due to isostatic uplift associated with deglaciation. The influence of future climate warming has the potential to offset this drying trend if increases in precipitation occur. Water availability for plant growth, in the Windmill Islands, will only increase, however, if precipitation levels both offset the current drying trend and also exceed the predicted increase in snow and ice melt associated with warmer temperatures. Based on our current knowledge of the physiological response of the Windmill Islands bryophyte species, combined with what we now know of their relative distributions, under increasingly wet conditions, we predict an increase in the extent of G. antarctici, and under drying conditions, a relative decline in G. antarctici and an increase the relative dominance of C. purpureus.
A strong TWC gradient existed between communities in January and was still apparent though weaker in February (Figure 3). Mean Turf Water Content (TWC) was highest in bryophyte communities, decreased from bryophyte to transitional communities by over half in January and more than 40% February, followed by a 18 to 19-fold decrease from transitional to lichen communities. For broad scale vegetation patterns, percent cover of live bryophytes significantly declined along the community gradient from 85% in bryophyte communities to 3% in lichen communities (Figure 4). The proportion of total bryophyte cover that was moribund increased from 10% in bryophyte communities to 55% in transitional communities and over 90% in lichen communities. Macrolichen cover was negligible in bryophyte and transitional communities, (0.5% to 1.5%) but increased to 40% in lichen communities where this vegetation type was co-dominant with moribund bryophytes (Figure 4). Crustose lichen cover and unvegetated cover were also highest in lichen communities. This demonstrates a transition from live to moribund bryophytes, and from bryophytes to lichens, with decreasing water availability. The same transition in vegetation from wet to dry areas was been observed at these locations in 1999-2000 (Wasley 2004), as well as in earlier studies of the Windmill Islands and other continental regions of Antarctica (Smith 1990a, Melick and Seppelt 1997, Brabyn et al. 2006). Under a drying climate regime, the lichen community will be an important place to detect vegetation change as live bryophytes exist in trace amounts and may disappear with large decreases in water availability. Another key indicator of drying will be the reduction in the ratio of live to moribund bryophytes in the transitional community, which at present is approximately 50:50. The community shift from bryophyte to lichen dominated vegetation under a drying climate is expected to be slow, due to the exceedingly slow growth rates of lichen species (Green 1985). Under a wetter climate, transitional communities have the potential to return to bryophyte communities as moribund bryophytes may regenerate if sufficient water becomes available. Water availability must be extensive and prolonged for this to occur (Melick and Seppelt 1997, Wasley et al. 2006a). In addition, a key indicator of vegetation response to increased water availability will be in the lichen community, where bryophytes may expand and out-compete lichens. This highlights the importance of monitoring lichen communities for trace live bryophytes to detect long term change, since there are parent live bryophyte propagules for potential expansion. At the finer scale, Schistidium antarctici dominated over 70% of bryophyte community samples, and declined to less than 10% and 2% dominance along the community gradient (Figure 5). In contrast, Ceratodon purpureus showed highest abundance in transitional communities, dominating 20% of samples. Abundance was intermediate in lichen communities, and was less than 2% in bryophyte communities. Differences in abundance between communities were found to be significant for both bryophyte species. The distinct species niches reflect the low tolerance of S. antarctici to desiccation requiring high water content for photosynthesis and growth combined with the ability to survive submergence events (Wasley et al. 2006b). C. purpureus is known to have high ability to avoid and tolerate desiccation and a relatively low tolerance to submergence (Robinson et al 2000, Wasley et al. 2006b). Thus, it is not surprising that C. purpureus occupies drier habitats in the Windmill Islands, co-occurring with lichens but still requiring some free water during the season. Under a drying climate, lower abundance of S. antarctici in transitional and bryophyte communities is expected, combined with further establishment of C. purpureus, particularly in this latter community where present abundance of C. purpureus is low. In contrast, a wetter future climate may see an increase in submergence events, which is likely to reduce the abundance of C. purpureus in bryophyte and transitional communities and restrict this species to drier lichen communities. Crustose lichen showed similar domination of samples in transitional and lichen communities, yet occurred in a greater percentage of samples in transitional communities. (Figure 5). Bryophyte communities contained crustose lichen in at least 15% of samples, which was significantly less than the other communities. Crustose lichen may establish on rocks in wetter communities and on bryophytes as they become moribund. Already established in drier communities, expansion of crustose lichen in bryophyte communities may relate to increased drying of bryophyte vegetation. Modern climate change is likely to occur at a rate fast enough for detection over decadal time intervals, or even sooner, since preliminarily analysis between the pilot and baseline study suggests species in bryophyte communities have shifted over a 3 year period. Other environmental changes in the region including drying due to isostatic uplift are likely to occur at a much slower rate. However, recent evidence suggests that this region is also experiencing more recent climate change induced drying (Hodgson et al 2006). While this indicator currently predicts vegetation changes with environmental change, future surveys commencing in 2007-08 will be able to confirm the impact of climate change on continental Antarctic communities. In addition, new survey methodologies to be employed in 2007-08, including digital image analysis, will allow enhanced change detection and improved data capture, storage and accessibility.
For definitions of the Scale categories, consult the Explanation of the Status Categories
|Registered File 2789 - Windmill Islands terrestrial vegetation dynamics - Summary sheets|
|Registered File 2836 - Windmill Islands terrestrial vegetation dynamics - Image files|
|SOE Indicator 1 - Monthly mean air temperatures at Australian Antarctic Stations|
|SOE Indicator 10 - Daily broad-band ultra-violet radiation observations using biologically effective UVR detectors|
|Taxonomy 100157 - Bryum pseudotriquetrum|
|Taxonomy 100163 - Cephaloziella exiliflora|
|Taxonomy 100169 - Ceratodon purpureus|
|Taxonomy 100173 - Grimmia antarctici|
There are no parameters set against this indicator.