Toxic Effect of a Pesticide, Diflubenzuron on Freshwater Microinvertebrate (Tetrahymena pyriformis)

Harmful bugs affect food production,directly by the qualitativeor quantitative reduction of the harvests,or indirectly while servinglike vectors of several illnesses of the plants and human[1].Many chemical products are used by human for a long time inthe…     

Population-level effects of augmented herbivory on Lespedeza cuneata: implications for biological control.

Invasive species pose significant ecological costs, and therefore successful management techniques are important. One commonly employed method is biological control. The success of biological control depends largely on whether additional inflicted damage can successfully reduce the fitness and population growth rate of a target species. Here, we simulate herbivory on the invasive Lespedeza cuneata and create stage-structured projection models to determine if augmented herbivory by a leaf-chewing biological control agent would regulate the population growth rate of this species. We found that augmented herbivory influenced stage transitions of plants in the smallest stage class, causing higher mortality and reduced growth. No other effect was found on stage transitions or fecundities, despite manipulation of herbivory at exceptionally high levels (up to 80% leaf loss). None of the clipping treatments significantly reduced the population growth rate of L. cuneata. We conclude that biological control by a leaf chewing herbivore would not likely be successful, even if an exceptionally large amount of each plant were consumed. We suggest that this approach, a combination of simulated herbivory and demographic modeling, will provide essential information for understanding the utility of biological control to curb the population growth of invasive plant species.     

Analysis of polychlorobiphenyls from used transformers for polychlorodibenzofurans

The results of analyses for polychlorodibenzofuran (PCDF) content in two samples of polychlorobiphenyl (PCB) from used electrical transformers are presented and discussed. In neither sample was there evidence for enhanced PCDF concentrations even though one of them had been subjected to overheating while in service.     

Polychlorodibenzo-p-dioxins and dibenzofurans in technical pentachlorophenol - results of a collaborative analytical exercise

Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed.     

Long term changes in polychlorodibenzo-p-dioxin concentrations in wood treated with technical pentachlorophenol

Wood samples treated with technical pentachlorophenol (PCP), technical sodium pentachlorophenoxide (NaPCP) and octachlorodibenzo-p-dioxin have been exposed outdoors for periods up to $\text{2}\text{1}\text{2}$ years. Analysis of extracts from the samples show that photolytic reductive dechlorination of highly chlorinated dibenzo-p-dioxins to less chlorinated isomers occurs. However there is no discernible increase in polychlorodibenzo-p-dioxin concentrations in the technical PCP treated wood presumably because further photolytic reactions and volatilisation compete effectively with the photolytic formation. There is no evidence for formation of octachlorodibenzo-p-dioxin (OCDD) in technical PCP treated wood in this study, probably because photolytic destruction and volatilisation compete effectively with formation reactions when the initial OCDD concentration is relatively high.     

Reduced rodent biodiversity destabilizes plant populations

We tested the hypothesis that species loss at one trophic level will reduce the temporal stability of populations at other trophic levels. We examined the temporal stability of annual plant populations on plots that experimentally manipulated the functional diversity of seed-eating rodent consumers. Experimental reduction of rodent functional diversity destabilized populations of small-seeded plants but had less consistent effects on larger-seeded species. Small-seeded species also exhibited a greater number of years of zero abundance. Thus, experimental reduction of rodent functional diversity resulted in lower plant diversity. The decline in the temporal stability of small-seeded plants likely resulted from increased interspecific competition by large-seeded plants. These results demonstrate that the loss of species at one trophic level can lead to reduced richness at lower trophic levels via competition and reduced temporal stability.