One of the longest running experimental manipulations in the world is the Old Man Range snowfence, built in 1959, Central Otago, New Zealand, for the purpose of manipulating snowpack. This snowfence ameliorates harsh alpine conditions in its lee, by reducing wind speeds and allowing snow to accumulate in winter and into spring. This effect has led to changes in soil nutrient availability and caused significant biological responses, and now resembles a naturally occurring snowbank community. Similarly, a snowfence built in 1994 on the Niwot Ridge, Colorado, USA, is producing similar effects. Despite the different plant species and their evolutionary histories, we questioned whether accumulating snow is leading to changes in ecological function at these sites and how fast these changes are happening. We measured community composition and plant traits (SLA, plant height, LDMC and leaf nitrogen) at two time intervals at both snowfences between 2010 and 2019. Overwhelmingly, graminoids and forbs, relatively taller and higher SLA species have higher abundances in the deep snow zones at both sites. Prostrate shrubs and tough, small species dominate the adjacent areas not affected by the snowfence. There were few significant changes in composition between our two sampling times, indicating that most of the substantial changes occurred much earlier in both the manipulations’ histories. Ecological functioning, inferred from the plant functional traits, also mirrors that of natural snowbanks. Our results suggest that future snowpack declines across alpine landscapes may lead to shrub dominated systems, with fewer tall, productive and competitive forb species.

Alpine ecosystems of the Australian mainland are among the most spatially and attitudinally restricted in the world placing them at a heightened risk from climate change. A major abiotic symptom of climate change in the low elevation mountains of the Australian Alps is decreased depth and duration of seasonal snow pack. To understand how alpine plants of this region will respond to reduced snow pack in a future of ongoing climate change, we conducted a snow removal experiment over two years in the Snowy Mountains of New South Wales.

In this experiment, we simulated conditions of significantly reduced winter snow pack and early spring snow melt, along with ambient snow pack controls, in forty one metre squared plots. During the snow-free seasons, we measured growth, reproductive phenology, and freezing damage in ten target angiosperm species encompassing 800 individual plants.

Complementary to our snow removal experiment, we quantified freezing resistance in the ten target species subjected to snow cover manipulations. Results from both the snow removal experiment and freezing resistance study will be presented.

Extreme temperatures and severe soil moisture deficits represent a major challenge for plant growth and survival in the Australian Alps. In the Australian alpine region, drought and heatwave frequency and intensity is expected to increase, and reductions in snowpack leading to earlier and more variable snowmelt may expose alpine plants to a greater number of radiative frosts. In addition, cooccurring drought and heatwaves could create conditions beyond the range of plant tolerances. Such extreme temperature events cause damage to the photosynthetic apparatus of plant tissue and represent a major survival challenge for Australian alpine plant species. In this study, ten common alpine shrub, forb and graminoid species were subjected to experimental reduction of rainfall in situ using passive rainout shelters in the Victorian Alps and Snowy Mountains. Shelters were installed for the duration a growing season (Nov-Mar). All species showed equally high frost and heat tolerance after one season of the rainfall reduction treatment compared to control individuals which received ambient rainfall. Australian alpine plants likely have relatively high drought resistance, as most areas experience soil moisture well below wilting point during late summer. These preliminary results demonstrate that a moderate reduction of soil moisture does not immediately induce an acclimation response in terms of plant heat and frost resistance in the short term.

Phenotypic plasticity is assumed to be a rapid mechanism that allows plants to cope in situ with adverse and new environmental conditions generated by climate change. For plasticity to be effective in allowing species to persist under climate change, it must be adaptive. However, despite the large body of literature on plant responses to temperature, only a handful of studies have actually tested whether they are adaptive. To address this gap, we exposed high and low elevation individuals of Wahlenbergia ceracea, an Australian alpine herb, to predicted future temperatures and heat waves, to characterize their plastic responses in several functional traits covering different aspects of the biology and ecology of the species (physiology, phenology, and allocation). We assessed the thermal tolerance and acclimation of photosynthetic machinery to high temperature using chlorophyll fluorescence. To investigate the association of plastic responses with fitness, we also measured reproductive traits (survival, number of flowers and capsules and capsules and seed mass) and estimated selection coefficients on reaction norms of different families using bivariate mixed effect models. Preliminary results show a differentiation between individuals over a small elevation gap in time to first flower and total number of flowers and capsules. Growth under warmer conditions caused a reduction in stem fresh mass and dry matter content as well as a reduction in fitness: individuals produced less capsules and most of them were empty. The adaptive value of the plastic responses of phenology, morphology and the thermal physiology will be discussed.

In the context of a rapidly warming climate, a research priority is to understand the germination strategies of native species from threatened communities. Temperature signals are assumed to be perceived by both the mother plant and the developing zygote, and are used to control the germination of progeny seed. We studied the warming effect on germination in an indigenous Australian alpine species Wahlenbergia ceracea. Seeds were bred under two contrasting temperature conditions (current cold, 20℃/15℃ day/night; warm, 30℃/25℃) and are genetically matched in these two developmental temperature conditions. All these seeds were moved through two series of temperature (current cold: 3 weeks at 20℃/15℃, 4 weeks at 5℃/5℃, 3 weeks at 20℃/15℃; warm: 3 weeks at 30℃/25℃, 4 weeks at 5℃/5℃, 3 weeks at 30℃/25℃), which mimic the seasons from autumn to winter to spring to determine the seasonal emergence pattern. Our results show that seed developed under warm condition has significantly reduced germination compared to seed developed under current cold condition. However, in spring, the germination of the warm developed seed is greater than that of cold developed seed (12.8% vs 9.4%). Interestingly, higher temperature increases germination regardless of the developmental temperatures and the seasons. We deduce that for the alpine species W. ceracea, the reduced germination of the warm developed seed is a consequence of temperature-induced dormancy, which does not decrease the germination in spring, and the warmer temperature does not appear to have a negative effect on offspring germination.

Coastal freshwater wetlands are highly vulnerable to climate change and the alteration of hydrology and salinity that is predicted with sea level rise (SLR). Investigating the response and resilience of wetland vegetation to predicted changes is important for understanding the threat that climate change poses and to help predict the potential impacts on wetland systems. Through in-situ manipulation of flooding and salinity regimes at a restored coastal freshwater wetland we investigated the responses of major wetland vegetation communities to simulated SLR. Repeat surveying of vegetation composition, structure and, condition was conducted in permanent plots established in Casuarina swamp, Melaleuca swamp, Salt Pan, and Riparian zone vegetation communities, to observe change over time. Groundcover species richness decreased in Salt Pan, Casuarina and, Melaleuca sites after 10 months of altered conditions. Decrease in overall vegetation cover was observed in response to altered conditions in Melaleuca and Casuarina sites, did not change in Riparian sites, but increased in one Salt-Pan site. Changes in woody vegetation community and structure were not observed in the short time period of this study, however recruitment and herbaceous regeneration were reduced. This suggests that vegetation transition first occurs in herbaceous species assemblages while changes in woody vegetation occur over longer timeframes. This study highlights the importance of investigation into the in-situ responses of coastal freshwater wetland vegetation communities to understand the likely trajectory of vegetation change in response to altered hydrology and increased salinity, as is predicted with climate change and rising sea levels.

Urban wetlands are increasingly being recognised as valuable conservation resources that support significant biodiversity. Concerns around the pest and public health risks of mosquitoes will restrict how we manage these wetlands, as outbreaks of mosquito-borne diseases fuel public fear and foster dislike of mosquitoes. Understanding the ecological and public health consequences of wetland management practices is vital to maximise the conservation value of urban wetlands without negatively impacting public health. Our aim was to determine how wetland management to benefit a threatened species affects mosquitoes and aquatic biodiversity.

A group of six urban wetlands in Sydney, Australia, were drained to reduce the abundance of an invasive fish, Gambusia holbrooki, and then refilled to provide breeding habitat for a threatened frog, Litoria aurea. We collected and compared aquatic macroinvertebrates, mosquito larvae, and mosquito adults from these refilled wetlands, and six adjacent undrained wetlands, on four occasions across summer and autumn.

Wetland draining had a significant effect on aquatic macroinvertebrates and larval mosquitoes, although differences between drained and undrained wetlands decreased over time. Draining did not affect adult mosquito assemblages associated with the wetlands.

The number of constructed and rehabilitated wetlands in urban areas continues to grow, and while conserving threatened habitats and species is imperative, our results highlight how wetland management can impact non-target species with potentially negative effects on humans. It is vital that future design and management of urban wetlands around the world also considers the impact on vectors of human disease.

Across Australian grasslands the invasive non-native buffel grass (Cenchrus ciliaris L.), has impacted heavily on native biodiversity and ecosystem function. In particular, large populations of buffel grass in the Spinifex (Triodia basedowii E.Pritz) grasslands of Central Australia have been ecologically detrimental and present a significant threat to indigenous culture. To effectively manage the current and future ecological impacts of buffel grass in these grasslands, it is vital to determine the most effective technique for reducing the abundance of the invasive grass both in the aboveground vegetation and in the belowground soil seedbank. Therefore, the aim of this study is to determine the efficacy of eight management strategies, which involve combinations of cool burning, mechanical removal and two herbicide treatments.
The experimental field trial conducted in Hermannsburg, NT indicates that cool burning as an overall treatment significantly reduced the abundance of buffel grass. However, similar reductions in abundance were found with both the mechanical and flupropanate treatments with no additional burning. Preliminary results from the seedbank germination trial indicate that buffel grass was abundant within the seedbank. However, a variety of other grass and forb species that were not observed in the aboveground vegetation were highly abundant in the seedbank. These results indicate that buffel grass can potentially have long-lasting ecological effects on spinifex grasslands. However, the aboveground vegetation can be controlled using mechanical removal or flupropanate herbicides, and the diverse seedbanks under the invaded areas could allow for the possibility of passive revegetation.

Temperate grasslands cover approximately 8% of the Earths’ surface and are one of the most diverse and productive terrestrial ecosystems. Despite this, they are critically endangered. Invasive species are widely accepted as one of the direct causes of grassland degradation across the globe. One such example is Nassella trichotoma which is considered one of the worst weeds for reducing biodiversity throughout Australia, New Zealand and South Africa. This hardy perennial is difficult to remove once established and herbicide resistant populations have emerged, encouraging the development of integrated control methods. Therefore, our objective is to identify the combined effectiveness of: glyphosate, fire, spot-spraying, tillage, fencing and broadcasting native grass seeds on reducing the soil seedbank, plant density and seedling recruitment of N. trichotoma. This trial is currently being conducted in a 10ha site managed by Parks Victoria. A total of 78 (12 treatments, 1 control x 6 replicates), 12m x 12m, plots were established with different treatments. Above ground vegetation was assessed using transect lines and soil seedbank densities were observed from collected soil cores. The preliminary results suggest that the fire treatment has increased recruitment of native grasses and reduced N. trichotoma foliage cover compared to the unburnt treatments. This study practically addresses the long-term management of this weed by focussing on (i) destroying the seed bank, (ii) removing the aboveground biomass and (iii) reducing grazing to enhance the competitiveness of the broadcasted seeds. This detailed knowledge will allow us to make confident management recommendations.

The east coast of Tasmania is home to the one of Australia’s last remaining Ostrea angasi shellfish reefs, an ecosystem that was once a dominant feature of many bays and estuaries in southern Australia. Traditional owners sustainably harvested these shellfish reefs for thousands of years, however, the arrival of Europeans spawned the first fisheries to target these reefs for local consumption, export, and to extract lime for construction. Shellfish reefs are now one of the most threatened ecosystems globally, with up to 99% lost in Australia.

Since 2014, The Nature Conservancy (TNC) and partners have embarked on an ambitious campaign to restore shellfish reefs across Australia, first in the Southern States, establishing a pilot project in Port Phillip Bay, Victoria and applying this proof of concept to a 20 hectare project in Gulf St Vincent, South Australia. TNC and partner led shellfish reef restoration activities are now established in Albany and the Perth regions of Western Australia, southern Queensland, with planning underway for Tasmania.

Outside of the US, Australia has led the way in shellfish reef restoration, adapting 15 years of US restoration experience to local conditions. This leadership role has been taken a step further, with Australia leading the publication of an updated Restoration Guidelines for Shellfish Reefs that included at worldwide team of editors and authors.

The establishment of an Australia-wide shellfish reef restoration campaign, which includes efforts to restore 30% of the original extent of shellfish reefs by 2025, will be discussed.

Future increases in the duration and intensity of drought are expected to cause widespread mortality in forest communities. The impacts of such broad-scale climatic changes may be exacerbated by biotic interactions among co-occurring trees that further increase the water deficit at the individual tree level. Using an experimental forest where the species composition has been manipulated, but abiotic variables (precipitation, soil type, temperature) remain constant, we assessed canopy damage of Eucalyptus regnans and Eucalyptus delegatensis trees after a significant drought event. After controlling for microsite variation using transect-level basal area as a proxy for productivity, we show that for both species, size was negatively correlated with the level of damage, such that smaller trees were more likely to have high levels of drought damage than larger trees. Furthermore, a plant’s neighbourhood strongly influenced the level of damage for both species, but the important neighbourhood characteristics differed between the two species. Drought damage in E. regnans increased with neighbourhood density, but damage in E. delegatensis was most sensitive to the number of Pomaderris apetala neighbours. Importantly, conspecific density was a strong predictor of damage for E. regnans only. We demonstrate that canopy damage patterns associated with drought can be explained, at least in part, by competitive neighbour interactions and smaller trees are far more likely to be affected than larger trees. These findings highlight the need to consider the composition and structure of natural communities to accurately predict forest mortality under future climate scenarios.

Leaf area index (LAI) is an important driver of primary productivity, and affects water and nutrient cycling. Extra leaves have both a cost and a benefit to a plant in terms of carbon and water balance and nutrient economics. Greater leaf area increases photosynthetic area, but also incurs a respiratory cost to the plant in terms of leaf construction and maintenance. Optimal leaf area is therefore influenced by the trade-off between carbon gains through photosynthesis and carbon loss through respiration, but is also influenced by transpirational demands. Furthermore, optimal leaf area responds to environmental factors such as nutrition, temperature and water supply.

Using three field experiments across a rainfall and temperature gradient in Tasmania, I investigated the way in which nutrient supply influences the optimal leaf area of the globally-important plantation tree, Eucalyptus nitens. Results show that the costs and benefits of extra leaf area depend on nutrient supply as well as site characteristics related to temperature and water. These results will contribute to the development of efficient nutrition management of production forests in southern Australia through an improved ability to predict and model the impact of fertiliser on productivity.