Floristic variation in Sphagnum-dominated peatland communities of the Central Highlands, Victoria

The floristic composition of Sphagnum-dominated peatlands in the Central Highlands region of Victoria was surveyed (37º 25´ S; 145º 50´ E). NMDS ordination and cluster analysis divided the peatland sites into two broad groups with altitude being the most important factor separating these groups. Other important factors were aspect, slope and the amount of shade. Group 1 included subalpine sites that are similar to those found at higher altitudes further east in Victoria. Important species included Empodisma minus, Epacris paludosa, Richea continentis and Baeckea gunniana. The two species of Sphagnum present were Sphagnum cristatum and the more inundation-tolerant Sphagnum novozelandicum. Group 2 included montane peatlands with abundant Sphagnum cristatum. These sites range from broad wet heaths dominated by Richea victoriana and Carex appressa, to narrower cool temperate rainforest and riparian systems. The ‘rainforest’ peatlands are characterised by Leptospermum grandifolium, Nothofagus cunninghamii, Carex appressa and Blechnum penna-marina, and are in varying stages of post-fire succession regulated by sitespecific microclimate. The conservation status and catchment function of these peatlands are briefly discussed

The 4.2 ka event in the vegetation record of the central Mediterranean

In this paper, the variation in forest cover in the central Mediterranean region, reflected by percentage changes in the arboreal pollen record, has been examined in relation to the 4.2 ka event. A total of 36 well-dated and detailed pollen records from latitudes between 45 and 36 degrees N were selected and their vegetation dynamics between 5 and 3 ka examined in relation to the physiographic and climatic features of the study area and to the influence of human activity on past vegetation, as suggested by anthropogenic pollen indicators. We have found that the sites located between 43 and 45 degrees N do not show any significant vegetation change in correspondence with the 4.2 ka event. Several sites located on the Italian Peninsula between 39 and 43 degrees N show a marked opening of the forest, suggesting a vegetation response to the climate instability of the 4.2 ka event. Between 36 and 39 degrees N, a forest decline is always visible around 4.2 ka, and in some cases it is dramatic. This indicates that this region was severely affected by a climate change towards arid conditions that lasted a few hundred years and was followed by a recovery of forest vegetation in the Middle Bronze Age. Human activity, especially intense in southern Italy, may have been favored by this natural opening of vegetation. In Sardinia and Corsica, no clear change in vegetation is observed at the same time. We suggest that during the 4.2 ka event southern Italy and Tunisia were under the prevalent influence of a north African climate system characterized by a persistent high-pressure cell

Local forest structure variability increases resilience to wildfire in dry western U.S. coniferous forests.

A 'resilient' forest endures disturbance and is likely to persist. Resilience to wildfire may arise from feedback between fire behaviour and forest structure in dry forest systems. Frequent fire creates fine-scale variability in forest structure, which may then interrupt fuel continuity and prevent future fires from killing overstorey trees. Testing the generality and scale of this phenomenon is challenging for vast, long-lived forest ecosystems. We quantify forest structural variability and fire severity across >30 years and >1000 wildfires in California's Sierra Nevada. We find that greater variability in forest structure increases resilience by reducing rates of fire-induced tree mortality and that the scale of this effect is local, manifesting at the smallest spatial extent of forest structure tested (90 × 90 m). Resilience of these forests is likely compromised by structural homogenisation from a century of fire suppression, but could be restored with management that increases forest structural variability

Plant Community Development in Storm-induced Overwash Fans of the Otis Pike Fire Island High Dune Wilderness Area, New York

Barrier island systems are driven by disturbance, climate, and geomorphology. Previously, barrier island vegetation communities were primarily described by microclimate variability. The purpose of this dissertation is to better understand effects of white-tailed deer on developing plant communities on barrier islands after a catastrophic disturbance. I used distance-based Moran\u27s eigenvector maps to identify spatial structures in vegetation communities of overwash fans in the third and fourth years after Hurricane Sandy. Spatial structures were present and significant at two or more frequencies in all overwash fans and explained the greatest amount of variation in vegetation community composition. Induced spatial dependence was predominantly controlled by proximity to foredune. I identified five biotic and abiotic influences to community composition in overwash fans and ranked their importance through canonical correspondence analysis. Gradients in productivity and elevation were primarily responsible for community composition and deer effects were not identifiable at the plot level. I identified effects of deer on vegetation cover and richness through a paired exclosure experiment, though only cover effects were statistically significant. Deer effects on cover were starker than those observed on species richness, suggesting assessments of deer effects on depauperate communities should focus on richness and cover. Lastly, I assessed effects of white-tailed deer on the rate of vegetation recovery in overwash fans through imagery classification and assessments of local white-tailed deer density. Though deer affect vegetation cover through trampling, grazing, and browsing in overwash fans, their effects on recovery rates were minimal and not statistically significant. Two overwash fans are expected to recover to pre-Sandy conditions within the decade since a nascent foredune is present and growing. Two overwash fans may never recover due to continued disturbance. The five remaining overwash fans have a slowly-forming nascent foredune, and changes in climate and frequency of storm events make their futures uncertain. Though deer do not pose a threat to the resilience of the barrier island, selective foraging behaviors may change composition and developmental trajectories of recovering vegetation communities over time

Climate change and disaster impact reduction

Based on papers presented at the 'UK - South Asia Young Scientists and Practitioners Seminar on Climate Change and Disaster Impact Reduction' held at Kathmandu, Nepal on 5-6 June, 2008