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Venn S.E.,New South Wales National Parks and Wildlife Service | Green K.,New South Wales National Parks and Wildlife Service | Pickering C.M.,Griffith University | Morgan J.W.,La Trobe University
Plant Ecology | Year: 2011

Environmental filters act to limit the local community assemblage from the regional species pool by restricting the viable trait states that can occur there. In alpine snowpatches, the timing of snowmelt is a strong environmental filter. In coming decades, the strength of this filter is likely to relax with global climate change. We used three continuous plant functional traits (leaf area, plant height, seed mass) and their divergence (using the FDvar index) to document current patterns of community assembly and predict plant community responses to future environmental filters in alpine snowpatch vegetation. The community trait-weighted mean for leaf area and height, but not seed mass, was significantly higher in early snowmelt zones relative to mid and late melting zones across all snowpatches. Mean FDvar for height (but not leaf area or seed mass), by contrast, was substantially lower in early snowmelt zones, indicating that species growing in early melt zones are consistently taller than those growing in other zones. These results suggest that if climate change leads to earlier snowmelt and hence, a longer growing season, taller (more competitive) species with larger leaf areas (more productive) may replace short species in snowpatches as these plant communities re-assemble in response to changing environmental filters. © 2011 Springer Science+Business Media B.V. Source

Vernes K.,University of New England of Australia | Green S.,University of New England of Australia | Thomas P.,New South Wales National Parks and Wildlife Service
Australian Mammalogy | Year: 2011

We undertook surveys of brush-tailed rock-wallabies (Petrogale penicillata) at four colonies in Oxley Wild Rivers National Park, north-eastern New South Wales, with the aim of developing a technique based upon individual animal recognition that could be used to obtain robust population estimates for rock-wallaby colonies. We identified individuals on the basis of distinct morphological characters in each colony using visual observations, and used the data within a 'mark-recapture' (or sight-resight) framework to estimate population size. More than 37h of observations were made over 10 sampling days between 18 May and 9 June 2010. We could identify 91.7% of all rock-wallabies that were independently sighted (143 of 156 sightings of 35 animals). A small percentage of animals could not be identified during a visit because they were seen only fleetingly, were in dense cover, or were partly obscured by rock. The number of new animals sighted and photographed declined sharply at the midpoint of the survey, and there was a corresponding increase in resighting of known individuals. Population estimates using the mark-recapture methodology were nearly identical to estimates of total animals seen, suggesting that this method was successful in obtaining a complete census of rock-wallabies in each colony. © 2011 Australian Mammal Society. Source

Pickering C.,Griffith University | Green K.,New South Wales National Parks and Wildlife Service | Barros A.A.,Griffith University | Venn S.,Griffith University | Venn S.,La Trobe University
Alpine Botany | Year: 2014

Alpine snowpatches are areas that, due to topographical and climatic factors, retain snow long after the thaw in the surrounding landscape. Within snowpatches there are often reliable patterns of snowmelt resulting in differences in plant composition, with snowpatch specialists limited to areas of late snowmelt. In 2013, we resurveyed vegetation in early, mid and late snowmelt zones across seven alpine snowpatches in the Snowy Mountains, Australia, 6 years after the initial 2007 survey. In both surveys, there were differences in vegetation cover and species composition among snowmelt zones; in particular, the cover of graminoids was higher in areas of earlier thaw. Differences in functional composition between survey periods were determined using functional traits (plant height, percent leaf dry matter content and specific leaf area) to calculate community trait-weighted means. In both surveys, early and mid snowmelt zones were dominated by taller species with larger leaves, mostly graminoids. Notably, by 2013 there was an increase in species richness in the late snowmelt zone and an increase in the cover of the tall tussock grass Poa costiniana across all snowmelt zones, driving changes in the community trait-weighted means for plant height and specific leaf area in the late snowmelt zone. The results highlight that snowpatch vegetation can change within relatively short time periods and that snowpatch plant communities may not remain as discrete units in the near future due to the encroachment of more competitive and productive species from the surrounding landscape. © 2014, Swiss Botanical Society. Source

Venn S.,Griffith University | Venn S.,La Trobe University | Pickering C.,Griffith University | Green K.,New South Wales National Parks and Wildlife Service
AoB PLANTS | Year: 2014

Classical approaches to investigating temporal and spatial changes in community composition offer only partial insight into the ecology that drives species distribution, community patterns and processes, whereas a functional approach can help to determine many of the underlying mechanisms that drive such patterns. Here, we aim to bring these two approaches together to understand such drivers, using an elevation gradient of sites, a repeat species survey and species functional traits. We used data from a repeat vegetation survey on five alpine summits and measured plant height, leaf area, leaf dry matter content and specific leaf area (SLA) for every species recorded in the surveys. We combined species abundances with trait values to produce a community trait-weighted mean (CTWM) for each trait, and then combined survey results with the CTWMs. Across the gradient of summits, more favourable conditions for plant growth (warmer, longer growing season) occurred at the lower elevations. Vegetation composition changes between 2004 and 2011 (according to non-metric multi-dimensional scaling ordination) were strongly affected by the high and increasing abundance of species with high SLA at high elevations. Species life-form categories strongly affected compositional changes and functional composition, with increasing dominance of tall shrubs and graminoids at the lower-elevation summits, and an overall increase in graminoids across the gradient. The CTWM for plant height and leaf dry matter content significantly decreased with elevation, whereas for leaf area and SLA it significantly increased. The significant relationships between CTWM and elevation may suggest specific ecological processes, namely plant competition and local productivity, influencing vegetation preferentially across the elevation gradient, with the dominance of shrubs and graminoids driving the patterns in the CTWMs. © 2014 The Author(s). Source

Venn S.,Griffith University | Venn S.,La Trobe University | Pickering C.,Griffith University | Green K.,New South Wales National Parks and Wildlife Service
Biodiversity and Conservation | Year: 2012

In response to climate warming, high altitude alpine vegetation may be replaced by typically lower altitude species, as species re-assemble and migrate to new areas. However, empirical evidence showing vegetation change in response to climate warming is largely unavailable for Australian alpine areas. Here, we examine changes in species richness with respect to climate and altitude over a 7 year period at a range of spatial scales in a re-survey of five alpine summits that are part of the Global Observation Research Initiative in Alpine Environments monitoring network. Eighty species were recorded in 2011 across all summits, an increase of 6 species since 2004. Mean species richness increased at the whole-of-summit scale from 45 to 50 species (about 12 %). At this scale, the rate of species richness increase was almost one new species per year, with 15 new species recorded at one summit. Here, shrub and graminoid species showed the largest increases. At the smaller spatial scales, changes in species richness were less pronounced. Turnover at the species and community level was typically moderate at all spatial scales and on all summits. The strength and direction of species richness change (the difference in species richness between the two sample periods, +/-) was not related to altitude nor variation in climate. Future re-surveys of the summits will confirm whether these short-term variations in species richness, particularly increases in shrubs, are indeed signals of longer-term trends and interactions with a changing climate. © 2012 Springer Science+Business Media B.V. Source

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