RESEARCH: Shrub Propagation Techniques for Biological Control of Invading Tree Species

Cornus stolonifera, Salix petiolaris, and Spiraea alba clones already located within the corridor of an electrical power line. To establish the efficiency of treatments, we examined the statistical differences of growth traits between species and treatments. An analysis of the effects of layering shows, after the first growth season, differences for all growth traits in only one species, Spiraea alba. After the second growth season, we observed the development of new aerial stems. Layering favors horizontal expansion of shrubs over height development. The third year after treatment, the effect of layering is reduced except for Cornus stolonifera, which continuously increases, as shown by the significant progression of the clone issued from the layer even five years after treatments. With the cutting back technique, we expected a distinct vertical growth of the shrubs at the expense of increasing the crown diameter. This technique would be best associated with the rejuvenation of clones, followed by a layering of new shoots to allow a horizontal expansion of the shrubs. Therefore, the formation of a dense shrub community by layering should be considered a valuable approach for the biological control of undesirable trees in powerline rights-of-way.     

Stability of a Coal Waste Artificial Reef

The feasibility of using U.K. coal-fired power station waste materials for artificial reef production is being examined. in June, 1989, an experimental artificial reef was constructed in Poole Bay, off the central south coast of the U.K., using three different mixtures of pulverised fuel ash (PFA), flue gas desulphurisation (FGD) gypsum and slurry, stabilized with cement and formed into blocks. Fifty tonnes of 40 × 20 × 20 cm blocks were formed into eight conical reef units replicating three different PFA/gypsum mixtures and one concrete control. the reef structure is 10m below chart datum on a flat sandy sea-bed.

Combustion of coal concentrates the heavy metal content in the resultant ash. the purpose of stabilization of the ash as blocks is twofold: to immobilize heavy metals (or other components) and to provide hard substratum for the attachment of organisms. to examine the effectiveness of this stabilization and hence the environmental compatibility of the block materials, heavy metal (Cd, Cr, Cu, Pb, Mn, Ni, Zn) content of the blocks has been monitored routinely over two years, to determine leaching rates. Sectional profiles indicate partial replacement of calcium content by magnesium. Associated with this there has also been some redistribution of heavy metals. Only in the case of cadmium has there been a detectable loss from the surface of blocks. Chromium and manganese concentrations appear to have increased. the metal content of the reef epibiota (including ascidians, Ascidia mentula; hydroids, Halecium spp.; bryozoans, Bugula spp. and red algae) growing on the ash blocks has been compared to that of epibiota attached to the concrete controls and surrounding sea-bed. to date no evidence of excess bioaccumulation of metals has been detected.

The physical integrity of the ash reef blocks has been maintained. There is evidence that the blocks are increasing in compressive strength.

An indication of the fishery enhancement potential of the experimental structure is given by the presence of eight commercially fished species (crustaceans and molluscs) including lobsters (Homarus gammarus).     

Role of vitamin A in the haematotoxicity of hexachlorocyclohexane (HCH) in the rat.

The haematotoxicity of technical hexachlorocyclohexane (HCH) (1000 ppm) was investigated in male albino rats fed with diet free of vitamin A or containing vitamin A at 2000 or 10(5) I.U./kg. Assessment of HCH-induced haematotoxicity at the end of the 7 weeks feeding period was done on the basis of haemoglobin content, total count of red blood cells and white blood cells and the differential counts of the white blood cells as well as by parameters such as packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin content, prothrombin time and clotting time. In the rats fed with vitamin A-free diet containing HCH, significant reductions were noticed in the total white blood cells count, clotting time and prothrombin time indicating severe haematotoxicity. Differential count of the white blood cells of these rats revealed a non-significant reduction in the lymphocyte count. The only indication of haematotoxicity caused by hexachlorocyclohexane in the vitamin A supplemented rats was a slight but statistically significant reduction of the total count of white blood cells. These results demonstrate that the haematotoxicity of hexachlorocyclohexane in the rats is enhanced by vitamin A-deficiency and its supplementation particularly in excess but not at hypervitaminotic level is protective against the toxicity.     

Composition of Floating Debris in Harbours of the United States

As part of a programme to characterize floating anthropogenic debris in the aquatic environment, the US Environmental Protection Agency (EPA) conducted 18 field surveys in the harbours of major metropolitan cities of the east, west, and Gulf coasts of the United States and the Mid-Atlantic Bight. the surveys were designed to provide information on the types, relative amounts, and distributions of aquatic debris in different geographic regions of the United States. Neuston nets (0.33 mm mesh) were used to collect surface debris during outgoing tides on two or three consecutive days in selected areas of each city. After each net tow, the debris, which ranged in size from small resin pellets to large plastic sheeting pieces, was identified, categorized, and counted. the data are being used to qualitatively characterize aquatic debris in coastal metropolitan areas, to examine potential regional variations, and to tentatively identify potential sources.     

Disposal of Mine Wastes Containing Pb and Zn Near the Ocean: An Assessment of Associated Environmental Implications in the Arctic

The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.     

Tolerance of calluna vulgaris and peatland plant communities to sulphuric acid deposition

Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6.