Bogong High Plains Research Articles

Carbon Storage and Fluxes from Sphagnum Peatlands of the Bogong High Plains, Australia

Australian alpine peatlands are critically important ecosystems that deliver a range of valuable services. However, our understanding of these services in Australia, particularly peatland carbon cycling, is lacking. Here, we quantified peat soil carbon (C) and nitrogen (N) concentrations, C:N ratios, and C density in eight Sphagnum-dominated peatlands on the Bogong High Plains, southeastern Australia. Soil C and N concentrations averaged 16.5 ± 13.2% and 0.6 ± 0.4%, respectively. C:N ratios averaged 30.9 ± 20.4, and C density averaged 46.6 ± 20.7 mg C cm− 3. Our findings suggest that (1) peat biogeochemistry is highly variable between sites, even at small spatial scales; and (2) while not a direct focus of the study, peat depths in this area were relatively shallow, ranging from 30 to 60 cm, most likely due to previous disturbance causing peat removal and carbon loss. Additionally, we present preliminary data investigating CO2 and CH4 fluxes at these sites. We recommend that future research includes (1) age dating peat cores to better understand the role of disturbance in rates of peat accumulation and loss; and (2) long-term carbon flux studies at multiple peatland sites.

Use of density‐impact functions to inform and improve the environmental outcomes of feral horse management

The available science often demonstrates the need for feral horse population control but not the degree of control required to achieve environmental conservation objectives. To better manage the influence of feral horses, we must first understand the relationship between feral horse density and environmental impact. We recorded vegetation and soil disturbance, and the sign of potential causes of this impact in two parts of the Australian Alps, the Bogong high plains (BHP) and the Eastern Victorian Alps (EVA). We calculated density‐impact functions to assist managers with determining feral horse density targets for control programmes. Minimal sign of feral horse impact was detected on the BHP, with no impact of feral horses observed along 99% of the length of transects. In contrast, impacts assigned to feral horses were significantly higher in the EVA, where a larger, higher‐density population of feral horses existed. However, greater than 83% of the walked transect length was still undisturbed by feral horses in the EVA. We detected a threshold of horse impact at ~ 250 horse faecal piles per ha. Above this threshold, a slight increase in horse density resulted in a disproportionately large increase in impact. In this context, a relatively small population control effort may substantially reduce direct horse impact. But where horse densities exist below this threshold, considerably more expense and control effort (resulting from the difficulties related to control at low density) is likely to make very little difference to an already low level of direct impact. The combined impacts associated with the sign of deer, feral pigs, fire and humans were large compared to that of feral horses. Management of feral horses to reduce their direct impact is unlikely to be beneficial without complementary management to reduce the effects of these other agents of impact.

<i>Corrigendum to</i>: Phylogenetics of the skyhoppers (<i>Kosciuscola</i>) of the Australian Alps: evolutionary and conservation implications

The true biodiversity of Australia’s alpine and subalpine endemics is unknown. Genetic studies to date have focused on sub-regions and restricted taxa, but even so, indicate deep divergences across small geographic scales and therefore that the bulk of biodiversity remains to be discovered. We aimed to study the phylogeography of the Australian Alps by focusing on the skyhoppers (<italic>Kosciuscola</italic>), a genus of five species of flightless grasshoppers whose combined distributions both span the region and are almost exclusively contained within it. Our sampling covered 650 km on the mainland and several sites in Tasmania with total of 260 specimens used to reconstruct a robust phylogeny of <italic>Koscisucola</italic>. Phylogenies were based on single nucleotide polymorphism data generated from double-digested restriction-associated DNA sequencing. Skyhoppers diverged around 2 million years ago and have since undergone complex diversification seemingly driven by climatic oscillations throughout the Pleistocene. We recovered not 5 but 14 clades indicating the presence of many unknown species. Our results support conspicuous geographic features as genetic breaks; e.g. the Murray Valley, and inconspicuous ones; e.g. between the Bogong High Plains and Mt Hotham. Climate change is progressing quickly in the region and its impact, particularly on snow, could have severe consequences for the skyhoppers’ overwinter survival. The true diversity of skyhoppers highlights that biodiversity loss in the Alps as a result of climate change is likely to be far greater than what can be estimated based on current species numbers and that management including small geographical scales is key.

A field experiment characterizing variable detection rates during plant surveys.

Surveys aimed at finding threatened and invasive species can be challenging due to individual rarity and low and variable individual detection rates. Detection rate in plant surveys typically varies due to differences among observers, among the individual plants being surveyed (targets), and across background environments. Interactions among these 3 components may occur but are rarely estimated due to limited replication and control during data collection. We conducted an experiment to investigate sources of variation in detection of 2 Pilosella species that are invasive and sparsely distributed in the Alpine National Park, Australia. These species are superficially similar in appearance to other yellow‐flowered plants occurring in this landscape. We controlled the presence and color of flowers on target Pilosella plants and controlled their placement in plots, which were selected for their variation in cover of non‐target yellow flowers and dominant vegetation type. Observers mimicked Pilosella surveys in the plots and reported 1 categorical and 4 quantitative indicators of their survey experience level. We applied survival analysis to detection data to model the influence of both controlled and uncontrolled variables on detection rate. Orange‐ and yellow‐flowering Pilosella in grass‐ and heath‐dominated vegetation were detected at a higher rate than nonflowering Pilosella. However, this detection gain diminished as the cover of other co‐occurring yellow‐flowering species increased. Recent experience with Pilosella surveys improved detection rate. Detection experiments are a direct and accessible means of understanding detection processes and interpreting survey data for threatened and invasive species. Our detection findings have been used for survey planning and can inform progress toward eradication. Interaction of target and background characteristics determined detection rate, which enhanced predictions in the Pilosella eradication program and demonstrated the difficulty of transferring detection findings into untested environments.

Distribution, composition and environmental correlates of high-altitude gravelly pavement herbfields in north-eastern Victoria, Australia

Context Gravelly pavement herbfields are a rare, geographically restricted community found in high mountain areas of south-eastern Australia. Gravelly pavement plant communities occur where there is continuous waterflow, with vegetation comprising sparse, semi-aquatic species on a rock or gravel substratum. Aims This study aimed to further the understanding of the community on the Bogong High Plains, Victoria, by asking questions relating to their location, structure and floristic composition. In particular, we ask what determines the distribution of pavement communities at the landscape-scale; and what abiotic factors govern between- and within-site vegetation patterns? Results Gravelly pavement communities were associated with groundwater outflows and are likely to be formed by an interaction between surface waterflow and slope. This work adds to the current understanding of wetland types in high-mountain Australia because, to our knowledge, this relationship has not been previously described. Floristic patterns vary with slope and elevation, with high-elevation pavements on steep slopes being floristically dissimilar to those at lower elevation on flatter slopes. Species richness was consistent across sites and only a few species were found at high abundance. Within-site patterning is apparent in most pavements, attributable to abiotic factors such as rockiness and water availability, leading to characteristic vegetation patterns. Species such as the sedge Oreobolus pumilio occur on the margins of pavements where water levels are variable, whereas forbs such as Psychrophila introloba are typically found in the middle of pavements where there is constant water supply. Conclusions Gravelly pavement communities are groundwater-dependant ecosystems, restricted at the landscape-scale and contain many rare species and, as such, deserve higher levels of protection than is currently offered.

Phylogenetics of the skyhoppers (

The true biodiversity of Australia’s alpine and subalpine endemics is unknown. Genetic studies to date have focused on sub-regions and restricted taxa, but even so, indicate deep divergences across small geographic scales and therefore that the bulk of biodiversity remains to be discovered. We aimed to study the phylogeography of the Australian Alps by focusing on the skyhoppers (Kosciuscola), a genus of five species of flightless grasshoppers whose combined distributions both span the region and are almost exclusively contained within it. Our sampling covered 650 km on the mainland and several sites in Tasmania with total of 260 specimens used to reconstruct a robust phylogeny of Koscisucola. Phylogenies were based on single nucleotide polymorphism data generated from double-digested restriction-associated DNA sequencing. Skyhoppers diverged around 2 million years ago and have since undergone complex diversification seemingly driven by climatic oscillations throughout the Pleistocene. We recovered not 5 but 14 clades indicating the presence of many unknown species. Our results support conspicuous geographic features as genetic breaks; e.g. the Murray Valley, and inconspicuous ones; e.g. between the Bogong High Plains and Mt Hotham. Climate change is progressing quickly in the region and its impact, particularly on snow, could have severe consequences for the skyhoppers’ overwinter survival. The true diversity of skyhoppers highlights that biodiversity loss in the Alps as a result of climate change is likely to be far greater than what can be estimated based on current species numbers and that management including small geographical scales is key.

Allopatric divergence drives the genetic structuring of an endangered alpine endemic lizard with a sky‐island distribution

AbstractAnthropogenic climate change is causing a world‐wide reduction of alpine habitat, leaving many high‐elevation species restricted to sky‐islands and vulnerable to extinction. Understanding the genetic parameters of these populations provides key insight into species diversity, dispersal capacity and vulnerability to disturbance. We examined the impact of past climatic variation on a threatened alpine endemic lizard, the Guthega skink, Liopholis guthega. We analysed SNP and mtDNA data to determine the population structure and phylogeny within this species, providing an understanding of the species’ relatedness, dispersal and viability. We identified significant genetic structure, with the split between populations in Koscuiszko National Park, New South Wales (NSW) and the Bogong High Plains, Victoria (VIC) consistent with Plio‐Pleistocene divergence. However, we also detected evidence of possible historical introgressive hybridization between some NSW populations and the VIC populations. Marked within‐site population structure and significant population differentiation among sites within each state were found, indicating a limited dispersal capacity. Higher levels of genetic diversity within NSW support the correlation between elevation and diversity and implicate Kosciuszko National Park as a historic refugia. Low contemporary habitat availability, little to no capacity for elevational progression and low genetic diversity, particularly in VIC, leaves L. guthega highly vulnerable to threatening processes associated with climate change. Conservation management should consider genetic rescue as a potential method to enhance genetic diversity across this species’ range.

Consistent temporal variation in the diet of an endangered alpine lizard across two south‐eastern Australian sky‐islands

AbstractA species' diet and feeding strategy directly affect fitness and environmental interactions. Understanding spatial and temporal variation in diets can identify key resources, inform trophic relationships, and assist in managing threatened species. The nationally endangered Guthega skink, Liopholis guthega, is restricted to two isolated Australian alpine plateaux, the Bogong High Plains (BHP) in Victoria and Kosciuszko National Park (KNP) in New South Wales. We compared this species' foraging ecology over the summer period between these ‘sky‐islands’ separated by ~100 km of lowland valleys. Scat composition did not differ between the two lizard populations, despite differences in the invertebrate assemblages present. However, L. guthega diet varied temporally over summer at both locations. Invertebrates, predominantly Hymenoptera and Coleoptera, were the dominant food group in early summer (78% volume (V), 100% frequency occurrence (F)) and mid‐summer (80% V, 100% F). A significant dietary shift occurred in late summer, when lizards consumed predominantly plant material (63% V, 95.5% F), consisting primarily of seasonally abundant berries from the snow beard heath, Acrothamnus montanus. In contrast to similar‐sized Egerniinae species, it appears L. guthega is capable of opportunistically shifting its diet towards plant material in response to temporal variation in resource availability. Furthermore, the prevalence of intact seeds in scats indicates L. guthega may play a significant role in seed dispersal. Understanding these trophic interactions will assist conservation management of L. guthega, allowing conditions for an already established captive colony to mimic the temporally variable diets present in situ, as well as informing revegetation initiatives aimed at maintaining and expanding wild populations.

Experimental warming and antecedent fire alter leaf element composition and increase soil C:N ratio in sub-alpine open heathland

Plant communities in alpine ecosystems worldwide are being altered by climate warming. In the alpine open heathland of the Bogong High Plains, Australia, warming and fire have affected the growth and phenology of plants, and have recently been found to alter soil nutrient availability. We examined the effects of nine years of passive warming by open-top chambers and nine years post-fire on (i) the soluble and extractable nutrients and toxic elements available for plant uptake in the soil and (ii) on the element composition of leaves of seven dominant sub-alpine open heathland plants. Warming increased soil C, soil C:N, and decreased soil δ13C, indicating an accumulation of soil organic matter and C sequestration. Warming increased soil δ15N, indicating increased N mineralization, which concurred with the increased availability of NH4+ (measured by ion-exchange membranes). Leaf element composition varied among the plant species in response to changes in soil element availabilities, suggesting the importance of species-specific knowledge. Warming decreased leaf N concentration and increased leaf C:N, generally in the plant community, and specifically in Asterolasia trymalioides, Carex breviculmis, Poa hiemata, and Rytidosperma nudiflorum. Warming increased soil P availability, but did not significantly affect leaf P in any species. Antecedent fire increased soil C:N, and decreased concentrations of Ca and Mg in Celmisia pugioniformis more than in the other species. The results suggest that warming and fire changed the nutrient composition of plants and increased soil C:N, which might lead to progressive N limitation in the alpine ecosystem.

Trouble at the top? Restricted distribution and extreme population isolation in an alpine crustacean assemblage with unexpected lineage diversity

Summary The fragile alpine freshwater ecosystems of Australia are threatened by historic land use and projected climate change, yet little is known about the fauna of these environments. The aim of this study was to analyse the phylogeography of two important components of this ecosystem, an amphipod (Neoniphargus) and an isopod (Coluboltelson), to determine the potential impacts of environmental change on these crustaceans. DNA sequences were generated for the mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 28S ribosomal RNA (28S) of 229 amphipods and 153 isopods from 19 sites across seven creeks in the Bogong High Plains, Victoria, Australia. Phylogenetic analyses were undertaken to define evolutionary significant units (ESUs), and population genetic structure was examined. Analyses of both markers found deep divergences in both taxa, leading to the definition of six amphipod and two isopod ESUs, within both Neoniphargus and Colubotelson. The majority of amphipod ESUs exhibited highly restricted distributions, with essentially no gene flow between sites, even within the same creeks, consistent with the Death Valley Model of population connectivity. By contrast, both isopod ESUs had overlapping distributions across the entire sample area and exhibited some highly limited population connectivity among sites in adjacent headwaters, consistent with the Headwater Model. This study suggests that there is a high level of undiscovered biodiversity within Australian alpine aquatic invertebrates. The highly limited population structure, and restricted distributions have important consequences for the conservation of the headwaters of Australia's largest river system. These findings indicate that habitat loss and/or fragmentation associated with environmental change will result in biodiversity reductions, with species unlikely to shift their ranges in response to future climate change, or recover rapidly from localised extinction events.

Chemical regulation of alpine headwater streams during a storm event (Bogong High Plains, Victoria, Australia)

The headwater streams originating in the Australian Alps are the highest water yielding landscape in South-Eastern Australia and are projected to be impacted by climate change through longer dry periods and more episodic rainfall. In this work we studied the major ion and DOC responses of three alpine peatlands (and the broader catchment containing these systems) to a high intensity (summer) storm event. Despite the high volume of rainfall, major ions in stream waters remained strongly chemostatic throughout the event. This was particularly the case for Ca2+ and Mg2+, as well as the alkalinity by association, and suggests that chemical regulation of these particular cations occurs through rapid equilibration processes. DOC concentrations increased during the storm pulse, leading to a shift in alkalinity partitioning from bicarbonate to organic anions and a decrease in pH, mediated by the CO2 saturation levels in the stream water. Our results suggest that alkalinity generation (Ca2+ and Mg2+ acquisition) and partitioning (DOC export) are decoupled processes that may respond differently to repeat storm events depending on the capacity of these systems to provide these constituents. Under extreme case scenarios depletion of DOC (at constant alkalinity) would lead to a smaller pH dip during a storm pulse, while depletion of alkalinity would lead to a larger pH dip, with buffering controlled by free acid. We have not identified the mechanism for the chemostasis of Ca2+ and Mg2+ (and therefore alkalinity) in this work, but this will be critical to understanding the capacity of these peatlands to respond to repeat and more intense storm events.

Extensive variation, but not local adaptation in an Australian alpine daisy.

Alpine plants often occupy diverse habitats within a similar elevation range, but most research on local adaptation in these plants has focused on elevation gradients. In testing for habitat‐related local adaptation, local effects on seed quality and initial plant growth should be considered in designs that encompass multiple populations and habitats. We tested for local adaptation across alpine habitats in a morphologically variable daisy species, Brachyscome decipiens, in the Bogong High Plains in Victoria, Australia. We collected seed from different habitats, controlled for maternal effects through initial seed size estimates, and characterized seedling survival and growth in a field transplant experiment. We found little evidence for local adaptation for survival or plant size, based on three adaptation measures: Home versus Away, Local versus Foreign, and Sympatric versus Allopatric (SA). The SA measure controlled for planting site and population (site‐of‐origin) effects. There were significant differences due to site‐of‐origin and planting site effects. An important confounding factor was the size of plants directly after transplantation of seedlings, which had a large impact on subsequent seedling survival and growth. Initial differences in plant width and height influenced subsequent survival across the growing season but in opposing directions: wide plants had higher survival, but tall plants had lower survival. In an additional controlled garden experiment at Cranbourne Royal Botanic Gardens, site‐of‐origin effects detected in the field experiments disappeared under more benign homogeneous conditions. Although B. decipiens from different source areas varied significantly when grown across a range of alpine habitats, these differences did not translate into a local or habitat‐related fitness advantage. This lack of local advantage may signal weak past selection, and/or weak adaptive transgeneration (plasticity) effects.

Fuels and landscape flammability in an Australian alpine environment

AbstractFactors governing landscape‐scale flammability are poorly understood, yet critical to managing fire regimes. Studies of the extent and severity of the 2003 Australian alpine fires revealed marked differences in flammability between major alpine plant communities, with the occurrence and severity of fire greater in heathland compared to grassland. To understand this spatial variation in landscape flammability, we documented variation in two physical properties of fuel – load and bulk density – at the life‐form and plant community scale. We measured the load (mass per unit area) and bulk density (mass per unit volume) of fine fuels (<6 mm) at 56 sites across the Bogong High Plains, southeastern Australia. Fine fuel load was positively correlated with shrub cover, and fine fuel bulk density was negatively correlated with shrub cover. Furthermore, fine fuel load and bulk density were accurately predicted using simple measures of canopy height and shrub cover. We also conducted a burning experiment on individual shrubs and snowgrass (Poa spp.) patches to assess comparative differences in flammability between these life‐forms. The burning experiment revealed that shrubs were more flammable than snowgrass as measured by a range of flammability variables. Consequently, our results indicate that treeless alpine landscapes of southeastern Australia are differentially flammable because of inherent life‐form differences in both fine fuel load and bulk density. If shrub cover increases in these alpine landscapes, as projected under climate change, then they are likely to become more flammable and may experience more frequent and/or severe fires.

In this issue – July 2015

In this issue – July 2015

Does Shelter Site Selection Aid Persistence of a Threatened Alpine Lizard? Assessing Liopholis guthega Populations a Decade after Severe Fire in Southeastern Australia

Species' tolerance of and response to fire varies. Environments that experience frequent fires will contain fire-tolerant fauna, whereas fauna that occur in environments that burn infrequently may lack strategies to cope with fire. In 2003, intense summer wildfires in southeastern Australia's alpine region burned more than 1.3 million ha. The Guthega Skink, Liopholis guthega, is an endangered lizard that is restricted to two geographically isolated alpine locations affected by these fires: Kosciuszko National Park in New South Wales, and the Bogong High Plains in Victoria. We investigated the long-term effects of fire on L. guthega populations through surveys of burned and unburned habitat on the Bogong High Plains. We found L. guthega selected specific microhabitats that are restricted on the Bogong High Plains. Their selection of less-vegetated microhabitats suggests that they may favor an early successional environment. We found retreat site selection differed between sites; at burned sites L. guthega burrowed preferentially under rocks, and at unburned sites comparatively more burrows were positioned at the base of shrubs. Our results suggest that in this species' Victorian range they may be more tolerant to fire than previously thought, likely because of the protection afforded by their burrows. However, our surveys of L. guthega populations from past records also suggest potential local extinctions. To determine the immediate and longer-term effects of intense fires on threatened species, it is important to have prefire data on species and prompt postfire assessments to obtain results applicable to management.

Genetic Structure ofCarexSpecies from the Australian Alpine Region along Elevation Gradients: Patterns of Reproduction and Gene Flow

Premise of research. Sixty percent of the vegetation in the alpine and subalpine region of Victoria, Australia, is endemic, making this region of prime importance for biodiversity and landscape conservation. Persistence of species under climate change may depend on genetic adaptation to changing environmental conditions, which in turn can be affected by patterns of gene flow and genetic variation for adaptive traits.Methodology. Carex hebes and Carex breviculmis are two sedge species commonly found across the Bogong High Plains of the Victorian alpine region. Carex hebes is common but restricted to alpine and subalpine areas, whereas C. breviculmis has a broader distribution. We used microsatellite markers to investigate the population structure of C. hebes and C. breviculmis along three elevation transects.Pivotal results. The genetic data indicated that both species reproduce mostly by sexual reproduction, with a low level of clonal (vegetative) reproduction. However, none of the populations sampled were at Hardy-Weinberg equilibrium, because of a high level of inbreeding in both species, resulting in a deficit of heterozygote individuals. Despite this, there was a high level of genetic diversity along all transects, with no associations between elevation and genetic diversity in C. breviculmis. There was an increase in inbreeding with elevation in C. hebes. The level of genetic differentiation between transects was low for C. breviculmis and higher for the more restricted species, C. hebes.Conclusions. These sexually reproducing species should have potential for adaptive shifts, although if inbreeding depression occurs it may result in lower fitness in both species, particularly for C. hebes at higher elevations.

Physical and chemical drivers of vegetation in groundwater-source pools on the Bogong High Plains, Victoria

The wetland communities intimately associated with groundwater sources in the Australian alps are poorly documented compared with the broader (and more obvious) alpine peatlands. In the present work, we report on the vegetation observed immediately around such sources and the characteristics of the supplying groundwater so as to understand the likely factors controlling the observed vegetation assemblage. Thirty-two groundwater sources were identified across three catchments on the Bogong High Plains, Victoria (Australia), and the vegetation associated with these sources surveyed. Groundwater sources occurred across a range of altitudes (1667–1854 m), independent of aspect, and were hydrologically connected to (upstream of) peatlands. Localised mounding adjacent to the groundwater sources resulted in the formation of pools (‘groundwater source pools’). The vegetation within the pools was dominated by bryophytes, with the aquatic bryophyte Blindia robusta the most common species. The groundwater was deficient in major ions, and similar to rainwater apart from elevated concentrations of CO2 accumulated in the groundwater-recharge process. The high CO2 concentrations, combined with the near-constant temperature conditions provided by sustained groundwater flow, are thought to be likely drivers for the high abundance of B. robusta. Although the relative contributions of rain and snow to aquifer recharge are not fully understood for the Australian Alps, these ecosystems are likely to be vulnerable to the changes in precipitation regime that are predicted under climate-change scenarios.

Experimental warming and long-term vegetation dynamics in an alpine heathland

High mountain ecosystems are vulnerable to the effects of climate warming and Australia’s alpine vegetation has been identified as particularly vulnerable. Between 2004 and 2010, we monitored vegetation changes in a warming experiment within alpine open grassy-heathland on the Bogong High Plains, Victoria, Australia. The study was part of the International Tundra Experiment (ITEX Network) and used open-topped chambers (OTC) to raise ambient growing-season temperatures by ~1°C at two sites. We assessed the effects of experimental warming on vegetation composition, diversity and cover using ordination, linear models and hierarchical partitioning. Results were compared with vegetation changes at four long-term (non-ITEX) monitoring sites in similar vegetation sampled from 1979 to 2010. The warming experiment coincided with the driest 13-year period (1996–2009) since the late 1880s. At the ITEX sites, between 2004 and 2010, graminoid cover decreased by 25%, whereas forb and shrub cover increased by 9% and 20%, respectively. Mean canopy height increased from 7 cm to 10 cm and diversity increased as a result of changes in relative abundance, rather than an influx of new species. These vegetation changes were similar to those at the four non-ITEX sites for the same period and well within the range of changes observed over the 31-year sampling period. Changes at the non-ITEX sites were correlated with a decrease in annual precipitation, increase in mean minimum temperatures during spring and increase in mean maximum temperature during autumn. Vegetation changes induced by the warming experiment were small rather than transformational and broadly similar to changes at the long-term monitoring sites. This suggests that Australian alpine vegetation has a degree of resilience to climate change in the short to medium term (20–30 years). In the long term (>30 years), drought may be as important a determinant of environmental change in alpine vegetation as rising temperatures. Long-term vegetation and climate data are invaluable in interpreting results from short-term (≤10 years) experiments.

Alpine road colonisation: An update

SummaryA wide road verge on the Bogong High Plains near Falls Creek (north‐eastern Victoria), stabilised with exotic species in the late 1950s, was monitored for species composition and cover between 1989 and 2010. Following the removal of cattle grazing in 1991, the cover and species richness of native shrubs, forbs and grasses increased on the verge. Changes were initially slow, but by 1999, they were profound. The cover of exotic species decreased over the same period, but the species richness of exotic species remained unchanged. A wildfire in 2003 did not alter the trajectories of change. Although native species are proving to be competitive, the exotic rhizomic grass Brown‐top Bent (Agrostis capillaris) has been very persistent and is still locally dominant. Feral horses and rabbits are future threats to the continued colonisation by native species.

Post‐fire regeneration in alpine heathland: Does fire severity matter?

AbstractFire severity is thought to be an important determinant of landscape patterns of post‐fire regeneration, yet there have been few studies of the effects of variation in fire severity at landscape scales on floristic diversity and composition, and none within alpine vegetation. Understanding how fire severity affects alpine vegetation is important because fire is relatively infrequent in alpine environments. Globally, alpine ecosystems are at risk from climate change, which, in addition to warming, is likely to increase the severity and frequency of fire in south‐eastern Australia. Here we examine the effects of variation in fire severity on plant diversity and vegetation composition, 5 years after the widespread fires of 2003. We used floristic data from two wide‐spread vegetation types on the Bogong High Plains: open heathland and closed heathland. Three alternative models were tested relating variation in plant community attributes (e.g. diversity, ground cover of dominant species, amount of bare ground) to variation in fire severity. The models were (i) ‘linear’, attributes vary linearly with fire severity; (ii) ‘intermediate disturbance’, attributes are highest at intermediate fire severity and lowest at both low‐ and high‐severity; and (iii) ‘null’, attributes are unaffected by fire severity. In both heathlands, there were few differences in floristic diversity, cover of dominant species and community composition, across the strong fire severity gradient. The null model was most supported in the vast majority of cases, with only limited support for either the linear and intermediate disturbance models. Our data indicate that in both heathlands, vegetation attributes in burnt vegetation were converging towards that of the unburnt state. We conclude that fire severity had little impact on post‐fire regeneration, and that both closed and open alpine heathlands are resilient to variation in fire severity during landscape scale fires.