No description available.

The urban environment has attracted much scientific attention as it stands at the core of environmental changes caused by the growing human population. The responses of bird communities to urbanization have been especially frequently studied. Despite the intensive research, there are several unresolved questions resonating in the field of urban ecology of birds: i) Are cities ordinary components of the original environment with the same macroecological bird diversity patterns as can be observed in the surrounding environment or do they have some specific impacts on native avifaunas? ii) Which traits are characteristic for species being able to persist in cities and for those avoiding urban areas? iii) How does the impact of the most important factors influencing urban bird communities - area, habitat heterogeneity and spatial position - change with spatial scale? Towards answering these questions, data on breeding bird communities were extracted from 41 European urban bird atlases, avifaunas of regions in which cities are embedded were retrieved from the EBCC Atlas of European Breeding Birds. Finer scale bird community data were obtained from the atlas of Prague and by point counts conducted in Prague. Data on bird traits were collated from published resources and additional environmental and...

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

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Coral bleaching and mortality caused by ocean warming is the largest threaten to modern coral reefs. Understanding the change and acclimatization of coral communities to warming temperature is urgent for management and conservation. Using transect photo-surveys and monitoring of natural substratum quadrats with fluorescence technique, we compare the community structure and recruitment of corals between a reef artificially heated by thermal outfall of a nuclear power plant for more than 25 years (Outlet) and a nearby natural reef (Hobihu) in Nanwan Bay, southern Taiwan. Both reefs are influenced by intermittent upwelling induced by internal wave. Abundance of hard corals in Outlet was significant higher than in Hobihu, while soft corals showed an opposite pattern. Coverages of corals such as Montipora spp., Porites spp., Galaxea spp. and Favia spp. were significant higher, but Seriatopora spp. and Stylophora spp. were significant lower in Outlet than in Hobihu. Coral recruitment rates were higher in Hobihu than in Outlet with Hobihu having more Pocilloporidae recruits while Outlet having more Euphylliidae, majorly Galaxea recruits. Coral recruitment rates and their survivorship were significant higher in spring/summer season than in autumn/winter season. These results suggest that elevated seawater temperature with other contrasting environmental conditions (different exposure and current) may change the structure of coral community by influencing differently on various life stages. Massive and encrusting corals may be more resilient to ocean warming.

Satellite images of chlorophyll concentration in the surface waters of the Gulf of Mexico suggest a high degree of heterogeneity in the phytoplankton biomass. The causes of this variability and the amount of variability in the phytoplankton community structure are not well understood. The physical and chemical conditions of a specific environment can influence phytoplankton community structure by selecting for those phytoplankton species able to survive within that environment. Varying salinity and temperature characteristics give water masses distinct surface water density signatures. This study examined the relationship between phytoplankton biomass, community structure, and different water mass properties by measuring chlorophyll a and algal group concentration across frontal zones. Continuous salinity and temperature measurements were used to calculate continuous density along transects during four cruises on the R/V Gyre between summer 2002 and spring 2004. Frontal zones were identified as areas of sharp density change where σt changed by 1.5 points over a distance of 1 km. Density fronts that coincided with visible temperature fronts (satellite AVHRR images) were selected for biomass and community structure analysis. Discrete water samples were analyzed using fluorometric analysis (total chlorophyll a concentration) and HPLC analysis (photosynthetic pigments). Community composition for discrete samples was determined using CHEMTAX and these values were used to interpolate community composition. Phytoplankton biomass and community structure were examined at a total of 21 density fronts. Unlike previous studies of frontal zones, phytoplankton biomass (measured as chl a concentration) was not significantly higher within frontal zones than in adjacent waters at any of the 21 fronts. Community composition (measured as algal group abundance and diversity) was significantly different between the front and at least one adjacent water mass at front 2 during summer 2002, at front 6 during summer 2003, at front 3 during fall 2003, and at front 3 during spring 2004. Both biomass and community composition were significantly different between fronts at all front pairs during summer 2002. The results of this study suggest that density fronts are not biologically important features in the northern Gulf of Mexico. Lack of high phytoplankton biomass at fronts in the Gulf of Mexico could indicate that unique physical, chemical, or biological processes are occurring.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Soil salinity is a widespread problem that affects crop productivity. We expect that saline soils also have altered microbial community structure, soil food webs and related soil properties. To test this, we sampled field soils across four farms in eastern North Dakota that host salinity gradients. We evaluated microbial biomass carbon, phospholipid fatty acid analysis and nematode counts in moderately saline and low saline soils. Additionally, we measured soil properties that represent potential food sources and habitat characteristics that influence microbial communities. We found higher microbial group abundance in moderately saline soils than in the lower saline soils. In contrast, we found lower nematode abundances in the moderately saline soils. We also observed increased labile carbon, nitrogen, phosphorus, and water content in the moderately saline soils. Based on our results, saline soils appear to have unique soil biological characteristics, which have implications for overall soil function along salinity gradients.

No description available.