Synthesis of effects in four Arctic subregions

An assessment of impacts on Arctic terrestrial ecosystems has emphasized geographical variability in responses of species and ecosystems to environmental change. This variability is usually associated with north-south gradients in climate, biodiversity, vegetation zones, and ecosystem structure and function. It is clear, however, that significant east-west variability in environment, ecosystem structure and function, environmental history, and recent climate variability is also important. Some areas have cooled while others have become warmer. Also, east-west differences between geographical barriers of oceans, archipelagos and mountains have contributed significantly in the past to the ability of species and vegetation zones to relocate in response to climate changes, and they have created the isolation necessary for genetic differentiation of populations and biodiversity hot-spots to occur. These barriers will also affect the ability of species to relocate during projected future warming. To include this east-west variability and also to strike a balance between overgeneralization and overspecialization, the ACIA identified four major sub regions based on large-scale differences in weather and climate-shaping factors. Drawing on information, mostly model output that can be related to the four ACIA subregions, it is evident that geographical barriers to species re-location, particularly the distribution of landmasses and separation by seas, will affect the northwards shift in vegetation zones. The geographical constraints--or facilitation--of northward movement of vegetation zones will affect the future storage and release of carbon, and the exchange of energy and water between biosphere and atmosphere. In addition, differences in the ability of vegetation zones to re-locate will affect the biodiversity associated with each zone while the number of species threatened by climate change varies greatly between subregions with a significant hot-spot in Beringia. Overall, the subregional synthesis demonstrates the difficulty of generalizing projections of responses of ecosystem structure and function, species loss, and biospheric feedbacks to the climate system for the whole Arctic region and implies a need for a far greater understanding of the spatial variability in the responses of terrestrial arctic ecosystems to climate change.     

Releases of phosphate fertilizer industry in the surrounding environment: Investigation on heavy metals and polonium-210 in soil

Distribution of Cu,Zn,Pb,Cr,Ni,Mn concentrations and the activity of polonium-210 in the surrounding area of a phosphate fertilizer industry located on the eastern coast of the Mediterranean Sea has been determined.Nineteen sampling sites were distributed around the industrial zone on a surface area of about 100,000 m2.Atomic absorption spectroscopy and Alpha spectroscopy were used to quantify the heavy elements and polonium-210,respectively.Investigation on a particle scale was conducted by TEM and SEM coupled to EDX and X-ray cartography to determine the nature of heavy elements carriers and their distribution.Heavy elements were mainly concentrated inside the particle size fraction 50 μm.Their levels decreased with distance increasing from the industry.According to the reference soil,enrichment factors were about 10,15,32 and 100 times for Zn,Pb,Cu,and Cr,respectively inside the particle size fraction 50 μm on the closest sites to the industry.The main contaminant sources were transport and storage of row materials and the free release of phosphogypsum waste.Heavy elements were entrapped inside agglomerates of sulfates,phosphates and iron oxihydroxides in a di used shape.Polonium-210 with an enrichment factor of about 56,showed the same behavior of the spatial distribution of the trace elements.     

Changes in functional structure of soil bacterial communities due to fungicide and insecticide applications in canola

The fungicide vinclozolin and insecticide λ-cyhalothrin are widely used to control canola (Brassica spp.) diseases and insect pests, respectively, in Canada. We investigated non-target effects of these pesticides, applied at recommended rates, on soil microbial biomass, functional bacterial diversity and functional community structure of soil bacteria (by evaluating patterns of C substrate utilization) in canola rhizosphere and bulk soil at three locations in Alberta from 2002 to 2004. Experimental treatments were (a) untreated control, (b) vinclozolin fungicide foliar application, (c) λ-cyhalothrin insecticide foliar application, and (d) vinclozolin and λ-cyhalothrin applications. No significant pesticide effects on soil microbial biomass or functional bacterial diversity were observed, but the functional structures of soil bacteria were altered. In 1 of 12 cases, the control treatment had a different soil bacterial community structure from the 3 pesticide treatments. The fungicide treatment had different bacterial community structures from the control or insecticide treatments in 3 of 12 cases, the insecticide treatment had different community structures from the control or fungicide treatments in 4 of 12 cases, and the combined fungicide and insecticide treatment had different community structures from the other treatments in 3 of 12 cases. Therefore, evaluating soil bacterial functional structures revealed pesticide effects that were not detected when bacterial diversity or microbial biomass were measured in canola rhizosphere or bulk soil.     

Soil microbial response to herbicides applied to glyphosate-resistant canola

Adoption of glyphosate-resistant canola (Brassica napus L.) has increased glyphosate applications to this crop, and concerns have been raised about unintended consequences of these multiple applications. A field trial was conducted to evaluate the effects of pre-seed and in-crop glyphosate and alternative herbicides on soil microbial community functional structure, diversity and biomass. Pre-seed treatments were 2,4-D, glyphosate and 2,4-D + glyphosate, and in-crop treatments were glyphosate applied once, glyphosate applied twice, ethalfluralin, ethalfluralin + sethoxydim + ethametsulfuron + clopyralid, and sethoxydim + ethametsulfuron. Rhizosphere and bulk soil was collected at flowering stage of canola and analyzed for bacterial community-level substrate utilization patterns and microbial biomass C (MBC). Where differences were significant, pre-seed application of both 2,4-D and glyphosate altered the functional structure and reduced the functional diversity of soil bacteria, but increased MBC. These effects were not necessarily concurrent. The reduction in functional diversity was due to reduction in evenness, which means that the soil where both pre-seed herbicides had been applied was dominated by only few functional groups. In 1 year, two in-crop applications of glyphosate also reduced the functional diversity of soil bacteria when applied after pre-seed 2,4-D, as did in-crop sethoxydim + ethametsulfuron following pre-seed glyphosate. Even though significant differences between herbicides were fewer than non-significant differences, i.e., there were no changes in soil microbial community structure, diversity or biomass in response to glyphosate or alternative herbicides applied to glyphosate-resistant canola in most cases, the observed changes in soil microbial communities could affect soil food webs and biological processes.     

Case study on nitrogen and phosphorus emissions from paddy field in Taihu region

The agricultural non-point source pollution by nitrogen (N) and phosphorus (P) loss from typical paddy soil (whitish soil, Bai Tu in Chinese) in the Taihu Lake region was investigated through a case study. Results shown that the net load of nutrients from white soil is 34.1 kg ha(-1) for total nitrogen (TN), distributed as 19.4 kg ha(-1), in the rice season and 14.7 kg ha(-1) in the wheat season, and for total phosphorus (TP) 1.75 kg ha(-1), distributed as 1.16 kg ha(-1) in the rice season and 0.58 kg ha(-1) in the wheat season. The major chemical species of N loss is different in the two seasons. NH4-N is main the form in the rice season (53% of TN). NO3-N is the main form in wheat season (46% of TN). Particle-P is the main form in both seasons, (about 56% of TP). The nutrient loss varied with time of the year. The main loss of nutrients happened in the 10 days after planting, 64% of TN and 42% of TP loss, respectively. Rainfall and fertilizer application are the key factors which influence nitrogen and phosphorus loss from arable land, especially rainfall events shortly after fertilizer application. So it is very important to improve the field management of the nutrients and water during the early days of planting.     

Occurrence of the Kumamoto oyster Crassostrea sikamea in the Ariake Sea, Japan

The Kumamoto oyster Crassostrea sikamea is distinguished from the closely related Pacific oyster C. gigas by concordant differences in 16S rDNA, allozymes, and a one-way gametic incompatibility. After repeated failures to find this oyster in its native habitat, we speculated in 1994 that “the Kumamoto oyster may be extinct in Japan”. In September 1996, we sampled small, deep-cupped oysters from the Ariake Sea and typed these for 16S rDNA and ITS-1 DNA markers previously shown to be diagnostic for the three most common oysters in the Ariake Sea, C. gigas, C. sikamea and  C. ariakensis. Our earlier suggestion of the demise of  C. sikamea proved incorrect. Of the 256 oysters sampled, 181 (71%) were  C. gigas, 53 (21%) were C. sikamea, and 22 (9%) were  C. ariakensis; no interspecific hybrids were observed. The distributions of C. sikamea and  C. ariakensis are clumped in the Ariake Sea:  C. sikamea occurs on the eastern and northern shores,  C. ariakensis occurs only in the northern part. These results emphasize the value of molecular markers for discriminating these morphologically plastic species both in the field and in aquaculture. Received 6 July 1998 / Accepted 8 October 1998     

Growth and lipid composition of scallop juveniles, Placopecten magellanicus, fed the flagellate Isochrysis galbana with varying lipid composition and the diatom Chaetoceros muelleri

The effect of feeding the flagellate Isochrysis galbana (Parke; clone T-Iso) of modified lipid composition on the growth and lipid composition of juvenile scallops [Placopecten magellanicus (Gmelin)] was investigated in the spring of 1993. I. galbana grown in 85-liter cage culture turbidostats under conditions of nitrogen limitation had a significantly higher total lipid content than when grown under nutrient-replete conditions. This was due mainly to a doubling in the amount of less unsaturated triacylglycerol in the cells. The concentrations of methyl and ethyl ketones were also greater in nitrogen-limited cells. Diets of nitrogen-limited I. galbana and nutrient-replete I. galbana grown in continuous and semi-continuous cultures were compared. Scallop juveniles were batch fed daily, and measurements of ingestion were determined. Samples of juveniles were removed periodically for determination of organic weight. The juveniles did not grow when fed nitrogen-limited or nutrient-replete I. galbana alone; however, when each diet was supplemented with 20% of the diatom Chaetoceros muelleri (Lemm.), there was a significant increase in growth in the juveniles receiving the nitrogen-limited I. galbana compared with juveniles on other diets. In comparison with I. galbana,  C. muelleri provided a rich source of carbohydrates and the essential fatty acid 20:4ω6. This study shows the importance of providing optimal dietary levels of ω3 and ω6 polyunsaturated fatty acids, as well as less unsaturated fatty acids and carbohydrates. Received: 29 September 1997 / Accepted: 2 October 1998     

Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

IntroductionCeramic,consistofearthymaterialslikeclaykaolin ,limestoneandsandglass .Ceramicmaterialsarenonmetalic ,inorganiccompoundsprimaryoxides ,alsocarbides ,nitridesandsilicides .Twotypesofbondingmechanismsoccurinceramicmaterial ,ionicandcovalent.Theo…