How Much Does Weather Matter? Effects of Rain and Wind on PM Accumulation by Four Species of Australian Native Trees

As interest in improving urban air quality grows, phytoremediation—amelioration through plants—is an increasingly popular method of targeting particulate matter (PM), one of the most harmful pollutants. Decades of research has proven that plants effectively capture PM from air; however, more information is needed on the dynamics of PM accumulation. Our study evaluated the effects of meteorological conditions on the dynamics of PM deposition, wash off and resuspension using four Australian tree species growing under natural conditions near a busy highway. Accumulation of PM on foliage was analyzed over the short term (daily changes) and over a longer time period (weekly changes). The results obtained were correlated with ambient concentrations of PM2.5 and PM10, rain intensity and wind strength. The highest accumulation of PM was recorded for Eucalyptus ovata (100.2 µg cm−2), which also had the thickest wax layer while the lowest was for Brachychiton acerifolius (77.9 µg cm−2). PM accumulation was highly changeable, with up to 35% different PM loads on the foliage from one day to the next. Importantly these dynamics are hidden in weekly measurements. Changes in PM deposition on the leaves was mostly affected by rain and to a lesser extent by wind, but the extent of the effect was species specific. The large PM fraction (10–100 µm) was the first to be removed from leaves, while the smallest PM fraction (0.2–2.5 µm) was retained for longer. Precipitation affects also PM retained in waxes, which until now were believed to be not affected by rain. This work demonstrates important interactions between PM load and weather, as well as adding to the small inventory of Australian native tree PM accumulation data.

Allocasuarina (Casuarinaceae) Invasion of an Unburnt Coastal Woodland at Ocean Grove, Victoria: Structural Changes 1971 - 1996

Changes in vegetation structure in a long-unburnt (> 115 years) woodland at Ocean Grove, Victoria, were assessed by comparing density data collected in 1971 by Withers and Ashton (1977) with comparable data from 1996. The changes in structure outlined by Withers and Ashton (1977) continued to operate over the 25 year period, namely, a dramatic increase in the density of Allocasuarina littoralis (Salisb.) L.A.S.Johnson, and a continued decline in the once-dominant eucalypts, especially Eucalyptus ovata Labill. The density of A. littoralis increased from 911 trees ha–1 in 1971 to 3565 trees ha–1 in 1996. Most of the surviving E. ovata displayed extensive crown dieback, and appear likely to die in the near future. Many eucalypt seedlings which were planted into burnt and unburnt experimental plots in 1971 were still alive in 1996, but most were less than 0.5 m tall and suppressed by tall regrowth of A. littoralis and Acacia pycnantha Benth. In the continued absence of fire and other disturbances, it is predicted that A. littoralis will continue to dominate the reserve, leading to further declines in eucalypts. It appears unlikely that a single fire will prevent A. littoralis dominance, and frequent burning at short intervals may be required to reinstate an open woodland structure.

948 PLANTING DENSITY EFFECTS ON CHARACTERISTICS OF SUN AND SHADE LEAVES OF EUCALYPTUS NITENS AND EUCALYPTUS OVATA.

Euculyptus ovata and E. nitens were analyzed for differences in leaf area (LA), leaf dry weight (LDW), leaf water content (LWC), specific leaf area (SLA), chlorophyll (chl), carotenoid (car), and protein (pro) content. A factorial design with 2 species, 3 densities (2340, 6490, and 12990 trees/ha), and 2 leaf exposures (sun and shade) was used. Low light appeared to have a greater affect on changes in leaf composition than planting density. Shade leaves of both species had higher LA, SLA, chl/LDW, car/LDW and chl:car and lower chl/LA car/LA, chl a:b and pro/LDW than sun leaves. Increased density resulted in higher SLA, chl:car ratio, and pro/LDW. Photosynthetic pigment accumulation was greater in shade leaves of E. ovata. E. ovata therefore, seems to adapt to shade through adjustment of the photosynthetic apparatus,while E. nitens adapted to low light primarily through increased SLA. SLA increased with greater planting densities and with decreased light intensity. The increase in SLA in shade leaves was greater in E. nitens, accounting for its greater biomass production over all planting densities in a related study.

Home-range estimates and habitat of the yellow-bellied glider (Petaurus australis) at Waratah Creek, New South Wales

The yellow-bellied glider (Petaurus australis), the largest of the exudivorous marsupials, lives in small family groupings and occupies virtually exclusive home ranges. A variety of estimation techniques were used to determine the home-range area of five glider groups. Two sets of data were analysed for each glider group; one included the locations of all observations while the other utilised a subset considered to represent independent observations based on a 3-h interval between consecutive locations. The techniques favoured for estimating home-range area, minimum convex polygon (MCP) and 95% isopleth of the harmonic mean (95% HM), gave mean values of 59 ha and 46 ha, respectively, when all data were included. These values were 28% and 14% larger, respectively, than those estimated with independent data. An extrapolation that accounted for the influence of the number of locations on the area estimated gave a mean MCP value of 63 ha for the five groups. This value was compared with estimates for other exudivorous mammals and is much greater than that predicted from the body weight of this species. The home ranges (defined by the 95% HM) of the five glider groups included different proportions of the seven forest types available in the study area. The forest type in which Eucalyptus ovata predominated was identified as a key habitat. It was the least abundant yet was included in all five home ranges, unlike several of the more abundant forest types which were absent from some home ranges. The above results are discussed in relation to forest management and conservation.

The Distribution of Arboreal Marsupials in Relation to Eucalypt Forest Types in the Eden (Nsw) Woodchip Concession Area.

Data collected during clear felling are collated and presented on the distribution of arboreal marsupials in 16 forest vegetation types (FVT) in 7 FVT groups. Eight species were included in the study: Petaurus breviceps, P. australis, P. norfolcensis, Petauroides volans, Acrobates pygmaeus, Trichosurus vulpecula, Pseudocheirus peregrinus and Cercartetus nanus. Most of the individuals reported were in the following 6 FVTs: swamp gum (characterized by Eucalyptus ovata); mountain gum (E. dalrympleana)/manna gum (E. viminalis); peppermint (E. radiata or E. dives); southern blue gum (E. maidenii, E. cypellocarpa or E. nitens); brown barrel (E. fastigata); and brown barrel/gum (E. cypellocarpa, E. nitens, E. maidenii, E. viminalis or E. dalrympleana). The results are discussed in relation to present forest management and forest clearing procedures in the Eden region. Forests about to be cleared for Pinus radiata plantations or for farmland on private property adjacent to State Forests are predominantly of types identified as of high value as wildlife habitat.

Preliminary Microscopic Investigations of the Digesta Derived From Foliage of Eucalyptus-Ovata (Labill) in the Digestive-Tract of the Common Ringtail Possum, Pseudocheirus-Peregrinus (Marsupialia)

A method is described that stabilizes vacuolar tannins in unchewed leaves of Eucalyptus ovata. This method, with light microscopy and electron microscopy, was used to study the fate of digesta in the gut of the common ringtail possum Pseudocheirus peregrinus. Normal animals (fed fresh foliage and practising coprophagy) were compared with animals denied access either to fresh foliage or to soft faecal pellets in the week before they were killed. Both manipulations appear to disturb gut function and create a need for caution in interpreting the observations. Nonetheless the results demonstrate some tanning of leaf cytoplasts in the ringtail possum, but the quantitative significance of the dietary losses so incurred is difficult to estimate. Partial digestion of cell walls and tanned cytoplasts occurs in the caecum, where massive populations of micro-organisms become attached to digestion-resistant tissue components. These 'microbial rafts' are reingested as soft pellets by coprophagy and the bacteria largely digested.