Alien plant invasions--incorporating emerging invaders in regional prioritization: a pragmatic approach for Southern Africa

Plant invasions are a serious threat to natural and semi-natural ecosystems worldwide. Most management-orientated research on invasions focuses on invaders that are already widespread and often have major impacts. This paper deals with "emerging" invaders-those alien species with the potential to become important problems without timely intervention. A climate matching procedure was developed to define areas of South Africa, Lesotho and Swaziland that could be invaded by 28 plant species that had previously been classified as emerging invaders. Information on the location of populations of these species in the study area was combined with information on their distributions (as native or alien) in parts of Australia and the United States of America. These two countries had the best available distribution data for this study. They also share many invasive alien plant species with South Africa. Climatic data obtained for weather stations near points of known occurrence in these countries were used to define the climatically suitable areas for each species in the study area. Almost 80% of the remaining natural environment in southern Africa was found to be vulnerable to invasion by at least one of these species, 50% by six or more and 24% by 16 or more species. The most vulnerable areas are the highveld grasslands and the eastern escarpment. The emerging invaders with the greatest potential range included Acacia podalyriifolia and Cortaderia selloana. The globally important invaders Ulex europaeus and Lythrum salicaria had a more limited invasion potential but could still become major invaders. There was no relationship between the extent of the climatically suitable areas for the different species and an expert ranking of their invasion potential, emphasising the uncertainties inherent in making expert assessments based on very little information. The methods used in this analysis establish a protocol for future modelling exercises to assess the invasion potential of other emerging invaders.     

Relationships between regulated DBPs and emerging DBPs of health concern in U.S. drinking water

A survey was conducted at eight U.S. drinking water plants, that spanned a wide range of water qualities and treatment/disinfection practices. Plants that treated heavily-wastewater-impacted source waters had lower trihalomethane to dihaloacetonitrile ratios due to the presence of more organic nitrogen and HAN precursors. As the bromide to total organic carbon ratio increased, there was more bromine incorporation into DBPs. This has been shown in other studies for THMs and selected emerging DBPs (HANs), whereas this study examined bromine incorporation for a wider group of emerging DBPs (haloacetaldehydes, halonitromethanes). Moreover, bromine incorporation into the emerging DBPs was, in general, similar to that of the THMs. Epidemiology studies that show an association between adverse health effects and brominated THMs may be due to the formation of brominated emerging DBPs of heath concern. Plants with higher free chlorine contact times before ammonia addition to form chloramines had less iodinated DBP formation in chloraminated distribution systems, where there was more oxidation of the iodide to iodate (a sink for the iodide) by the chlorine. This has been shown in many bench-scale studies (primarily for iodinated THMs), but seldom in full-scale studies (where this study also showed the impact on total organic iodine. Collectively, the THMs, haloacetic acids, and emerging DBPs accounted for a significant portion of the TOCl, TOBr, and TOI; however, ∼50% of the TOCl and TOBr is still unknown. The correlation of the sum of detected DBPs with the TOCl and TOBr suggests that they can be used as reliable surrogates.     

Postemergence Control of Microstegium vimineum on Riparian Restoration Sites with Aquatic‐Use Registered Herbicides

Microstegium vimineum is an invasive grass introduced from Asia that has spread throughout riparian areas of the eastern United States threatening native riparian vegetation. Postemergence (POST) herbicides registered for aquatic use were evaluated for control of M. vimineum on two riparian restoration sites in the Piedmont and Upper Coastal Plain of North Carolina. This study found that standard and lower than standard rates of diquat, fluridone, flumioxazin, glyphosate, imazamox, and imazapyr reduced weed stem density and biomass at 6 and 30 weeks after treatment (WAT). Both rates of bispyribac and penoxsulam provided less control of M. vimineum. Visual ratings showed both rates of diquat, flumioxazin, imazamox, and imazapyr controlled 63‐100% of M. vimineum at 6 WAT and 84‐100% at 30 WAT. Fluridone and glyphosate provided slightly less control. Bispyribac and penoxsulam treatments provided less control at 6 and 30 WAT compared to the other treatments. Plots treated with both rates of diquat, flumioxazin, imazamox, and imazapyr were nearly devoid of all vegetation at 30 WAT. Recommendations include POST application of lower than standard rates of diquat, flumioxazin, fluridone, glyphosate, imazamox, and imazapyr on riparian restoration sites infested with M. vimineum. Immediate vegetation management measures including temporary and permanent plant cover should be employed on treated sites where weeds are completely eradicated to prevent erosion.     

Social structures,genetic structures and dispersal strategies in Australian rabbit (<Emphasis Type="Italic">Oryctolagus cuniculus</Emphasis>) populations

In this study, the pattern of movement of young male and female rabbits and the genetic structures present in adult male and female populations in four habitats was examined. The level of philopatry in young animals was found to vary between 18-90% for males and 32-95% for females in different populations. It was skewed, with more males dispersing than females in some but not all populations. Analysis of allozyme data using spatial autocorrelation showed that adult females from the same social group, unlike males, were significantly related in four of the five populations studied. Changes in genetic structure and rate of dispersal were measured before and during the recovery of a population that was artificially reduced in size. There were changes in the rate and distance of dispersal with density and sex. Subadults of both sexes moved further in the first year post crash (low density) than in the following years. While the level of dispersal for females was lower than that of the males for the first 3 years, thereafter (high density) both sexes showed similar, low levels of dispersal (20%). The density at which young animals switch behaviour between dispersal and philopatry differed for males and females. The level of genetic structuring in adult females was high in the precrash population, reduced in the first year post crash and undetectable in the second year. Dispersal behaviour of rabbits both affects the genetic structure of the population and changes with conditions. Over a wide range of levels of philopatry, genetic structuring is present in the adult female , but not the male population. Consequently, though genetic structuring is present, it does not lead to inbreeding. More long-distance movements are found in low-density populations, even though vacant warrens are available near birth warrens. The distances moved decreased as density increased. Calculation of the effective population size (N_e) shows that changes in dispersal distance offset changes in density, so that N_e remains constant.     

Soil washing for volume reduction of radioactively contaminated soils

The Office of Radiation and Indoor Air of the U.S. Environmental Protection Agency has demonstrated a soil washing plant for the treatment of radioactively contaminated soils from two Superfund sites in New Jersey. The plant employs unit operations that are widely used in the processing of minerals and coal. These operations were examined and tested to determine how they would apply to volume reduction of these contaminated soils. In this context, they are considered to be innovative candidates for remediation of other sites with large volumes of soil contaminated with low-level radioactivity. Laboratory testing of soil characteristics and behavior in unit processes is used to assess the applicability of volume reduction/chemical extraction (VORCE) technology to specific sites.     

Leafyeasts as indicators of air quality in Europe

Leafyeast populations were surveyed in 1987 and 1988 with the help of schoolchildren at 23 centres throughout Europe located at Brussels, Rochfort-Marche, Flobecq-Renaix and Tournai (Belgium); Aberdeen and Halifax (Britain); Lyon, Rouen and Toulouse (France); Hamburg, Koblenz and Stuttgart (Federal Republic of Germany); Banbridge, Belfast, Dublin and Enniskillen (Ireland); Hollenfels and Ettenbruck (Luxembourg); Apeldoorn, Deventer, Harlem, Leiderdorp and Zutphen (Netherlands). From one to one hundred schools were involved at each centre. The results demonstrate the suitability of leafyeasts for assessing air quality in both urban and rural areas of the non-Mediterranean countries of Europe. Low counts are associated with known pollution sources. As leafyeast populations change quite quickly, the effect of weather systems on the impact of pollution clouds from urban/industrial areas can be followed. Leafyeasts thus give information complementary to that from traditional biological monitors like lichens which provide an integrated picture of the pattern of air pollution over the months or years prior to study.     

Novel features of an inducible defense system in larval tree frogs (Hyla chrysoscelis)

Organisms in aquatic ecosystems must often tolerate variable environmental conditions, including an uncertain risk of predation. Individuals that can maintain plastic defenses against predation will increase their survival when predators are present, but will not incur the costs of these defenses when the risk of predation is low and the defense is not induced. Larvae of the pond-breeding anuran Hyla chrysoscelis develop a conspicuous phenotype in the presence of predators consisting of a brightly colored tail and a deeper tail fin. In this study, I attempted to identify the source of the chemical signal that induces this defensive morphology in this species. I tested whether metabolites alone, originating from the prey but passing through the predator, were able to induce the same morphological response as the combination of alarm signals released directly by attacked conspecifics, and metabolites. I used morphometric and tail conspicuousness data to assess tadpole response to the perceived risk of predation by larval odonate predators (Anax junius). I also tested whether this inducing cue could be recognized across species by measuring the morphological response of H. chrysoscelis tadpoles exposed to cues emitted when tadpoles of a closely related genus (Pseudacris crucifer) were consumed. Tadpoles exhibited a clean graded response of both overall shape and tail morphology in response to all cues, corresponding to their relative reliability as indicators of a risk of predation. H. chrysoscelis tadpoles were also able to respond to cues emitted when tadpoles of a closely related genus were consumed by predators. These results illustrate that tadpoles of this species are able to respond to metabolites alone without alarm signals, and that interspecific chemical communication is a primary mechanism for predator avoidance in this inducible defense system.     

Shale weathering profiles show Hg sequestration along a New York–Tennessee transect

Environmental Geochemistry and Health - Shale-derived soils have higher clay, organic matter, and secondary Fe oxide content than other bedrock types, all of which can sequester Hg. However, shales...     

Northeastward reverse migration of birds over Nova Scotia,Canada, in autumn

Summary During 4 seasons of study, small numbers of birds flew overland to the NNE-E, counter to the main SW migration, intermittently throughout the autumn (31 July – 16 November). Radars also detected overwater reverse migration (RM) from New England to Nova Scotia and from Nova Scotia toward Newfoundland. RM occurred at all hours of the day and night, especially when few birds were migrating SW. Most but not all cases of RM occurred with following SW winds. RM was more common with cloud and/or poor visibility than in fair weather, but was not restricted to cloudy occasions. Mean tracks were correlated with wind direction, but were not consistently downwind. Tracks tended to be closer to downwind in early than in late autumn, and on clear than on overcast nights. Dispersion in tracks was not discernibly related to weather variables, time of day or night, or magnetic disturbance. Eleven hypotheses concerning the reasons for reverse migration in autumn are evaluated; cases of RM recorded in this study are attributable to at least three of these hypotheses (late summer dispersal, hurricanes, dawn reorientation toward coast) and possibly to several others.     

Chlorinated hydrocarbon contaminants in Hong Kong surficial sediments.

Twenty surficial sediments were sampled from nearshore Hong Kong waters during 1997-1998, and analyzed for a range of chlorinated pesticides and polychlorinated biphenyls (PCBs). Results showed that concentrations (on a dry weight basis) of total HCHs were in the range 0.1-16.7 ng g-1, and total DDTs 0.3-14.8 ng g-1. PCBs, measured as an Aroclor 1242, 1248, 1254, 1260 (1:1:1:1) mixture, were found to be in a range of 0.5-97.9 ng g-1, and were at highest concentrations in Victoria Harbour. Results indicated that chlorinated pesticides and PCBs in Hong Kong nearshore sediments were most likely derived from waste discharge from a variety of sources, including agricultural, sewage, industrial waste disposal and shipping-related activities. In addition, as the north and west sides of Hong Kong are subject to influence from the Pearl River (due mainly to agricultural activities in the Pearl River Delta, and to a lesser extent developments around the Shenzhen Special Economic Zone), these inputs are also thought to be likely sources of contamination.