Herbicide impacts on exotic grasses and a population of the critically endangered herb "Calystegia affinis" (Convolvulaceae) on Lord Howe Island

Introduced perennial grasses are capable of altering the habitat of native species, causing reductions in population size and vigour, and potentially affecting life-history processes such as survival, pollination and seedling recruitment. We examined the utility of herbicide treatment on two exotic grasses, Pennisetum clandestinum (Kikuyu) and Stenotaphrum secundatum (Buffalo grass) to restore the habitat of Calystegia affinis, a critically endangered species endemic to Lord Howe and Norfolk Islands. Using two herbicides, Asset (designed to affect only grasses) and Glyphosate (a general herbicide), we compared effectiveness in reducing grass cover on a population of Calystegia affinis. We protected Calystegia plants from the herbicides by ensuring their leaves were covered by plastic bags during herbicide application. Both herbicides were similarly effective in reducing grass cover after four weeks and had no noticeable adverse affect on Calystegia (suggesting the plastic bag protection was effective). After 26 weeks, Glyphosate was more effective in maintaining a reduced grass cover. Plots treated with either herbicide had a greater relative increase in abundance of Calystegia stems compared to untreated controls. The Glyphosate treatment resulted in the greatest relative increase in stem abundance, but this was not significantly greater than in the Asset treatment. We consider that spraying with Glyphosate treatment, with follow-up monitoring and spot-spraying, will assist the recovery of the Calystegia affinis population. Ultimately, the maintenance of a weed-free zone at the forest edge will provide suitable habitat for additional recruitment of this and other native species

Is There an Environmental Kuznets Curve for Sulfur?

The environmental Kuznets curve (EKC) hypothesis proposes that there is an inverted U-shape relation between environmental degradation and income per capita. Various explanations for this phenomenon have been put forward and some authors argue that important explanatory variables are omitted from conventional EKC estimates. Inclusion of these omitted variables is argued to increase the estimated "turning point" - the level of GDP per capita above which environmental degradation is declining. In this paper we use a new cross-section/time-series data base of sulfur emissions for a wide range of developed and developing countries. The methodology involves estimating EKCs for subsets of this database as well as for the sample as a whole. The results show that estimating an EKC using data for only the OECD countries, as has often been the case, leads to estimates where the turning point is at a much lower level than when the EKC is estimated using data for the World as a whole. The paper explores possible explanations of these results using Monte Carlo analysis, and other statistical tests.We conclude that the simple EKC model is fundamentally misspecified and that there are omitted variables which are correlated with GDP

Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats

Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is difficult because the presence of adult plants may mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (\50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruitremoval was widespread but less (20–54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island

Population Ecology of Waratahs, Telopea speciosissima (Proteaceae): Implications for Management of Fire-prone Habitats

Waratah (Telopea speciosissima) post-fire floral displays are a prominent feature of the landscape in Royal National Park and elsewhere in southeastern Australia, but factors governing the persistence of the species are poorly known. We examined long term patterns of fecundity, recruitment and survival of waratahs in Royal NP in relation to two major wildfires. Flowering occurred mainly over 3 years following both the 1994 and 2001 fi res, but fewer plants flowered, fewer seeds were produced and fewer seedlings established after the 2001 fi re. After the 1994 fire, limited seed dispersal resulted in most seedlings establishing near fruiting individuals. Only 14% of the plants that established as seedlings after the 1994 fire survived the 2001 fire. At the time of the 2001 fi re, these plants were 4-6 years old and post-fire survival was highest in older plants. A logistic model predicts that it would take 5.9 (95% CI 5.4-7.5) years of growth after germination for plants to have greater than 25% survival probability if burnt (equivalent to a fire return period of about 9 years). Waratahs are long lived, have long primary juvenile periods and occasional opportunities for recruitment. Each fire may not lead to successful recruitment. While recruitment failure after one or more fires may not be significant, understanding the proximate factors that limit recruitment is important to predict the impact of long term changes such as altered fire regimes under a changing climate

Assessing the conservation status of the grass Elymus multiflorus subsp. kingianus on Lord Howe Island, NSW

The grass Elymus multiflorus subsp. kingianus (family Poaceae) is considered to be endemic to Lord Howe and Norfolk Islands. We assessed the conservation status of the taxon on Lord Howe Island, New South Wales, and undertook targeted field surveys across three years and several seasons in suitable habitat, based on the single previously recorded location. We found the species occurrence on Lord Howe Island was highly restricted, with only a few plants found at 2 locations in close proximity. A number of exotic grasses pose a threat to the long-term conservation of the taxon, which was assessed as being eligible for listing as critically endangered under the NSW Threatened Species Conservation Act 1995

Persistence ability of soil seed banks in burnt landscapes

Seed banks play a critical role in the persistence of plant populations in variable environments. In the context of fire, seed banks are a particularly important source of seed for species which are killed by fire and rely on seed stored in the soil to regenerate and persist in the landscape following such disturbance events. Fire severity can vary, depending on a number of factors including: intensity, duration of the fire, fuel loads, fuel and vegetation type, topography, climatic condition, soil texture and moisture, soil organic content, time since last fire and area burnt. Essentially fires that consume a large amount of fuel can result in greater heat penetration of the soil profile, greater soil temperatures and longer residence times during the passage of fire. This is particularly important for species with a soil-stored seed bank as heating of soil may promote or inhibit the germination of seeds in the soil and affect the regeneration of species following fires of different severities. I examined the soil seed banks of five different plant communities in the Gibraltar Range and Washpool National Parks, New South Wales, Australia. The five communities ranged from those dominated by mesic elements with low fire frequency (Wet Sclerophyll Forest and Rainforest), to those with a strong sclerophyll component and a relatively higher expected fire frequency (Dry Sclerophyll Forest, Rocky Outcrop and Wet Health). This thesis consists of five data chapters, each written in the style of a scientific paper

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy