The diversity of microorganisms and the influence of their enzymatic activities in soil are critical to the maintenance of good soil health. Changes in these parameters may be the earliest predictors of soil quality changes, potentially indicating anthropogenic influences. The goal of this study was to investigate the soil microbial diversity and function of grasslands along an urbanization gradient. Soil samples were collected in the Potchefstroom municipal area, South Africa, at specific sites. Sampling sites were described as urban, suburban and rural - according to the V-I-S (Vegetation-Impervious surface-Soil) model of Ridd (1995). Soil samples were collected over a warmer, wet season (May) and a colder, dry season (August) over two years (2007 and 2008). Collected soil samples were characterised using certain physical and chemical parameters. Plant species composition and abundance were determined at each site, along with basic site data (soil compaction, percentage ground cover, percentage bare ground, percentage organic material present). The Shannon-Weaver diversity index was used to calculate biodiversity values for all the investigated sites regarding collected plant species composition. The microbial component of the soil was quantified and characterized using culture-dependent and culture-independent techniques. Culture-dependent techniques included the investigation of the aerobic heterotrophic bacteria and fungi. Organisms were plated out on different media, and the bacterial component was broadly grouped using morphology. Dominant organisms were identified by sequencing of PCR amplified 16S ribosomal DNA fragments. Shannon-Weaver index for bacterial diversity was determined for each of the sites. Denaturing gradient gel electrophoresis (DGGE) profiling of selected bacterial communities were also conducted. Microbial community function was determined using enzyme assays of five major groups of enzymes, namely (i) dehydrogenase; (ii) β-glucosidase; (iii) acid phosphatase, (iv) alkaline phosphatase and (v) urease. Plant species results were then brought into context with microbiological diversity and functionality results using multivariate statistics. Physical and chemical parameters of the collected soil samples revealed patterns present along the urbanization gradient. The pH values were mostly higher in the sub-urban and urban sites than in the rural sites. Electrical conductivity values were generally highest in the sub-urban sites. Plant species composition revealed trends along the urbanization gradient. Ordinations clearly grouped the plant species into rural, sub-urban and urban groups regarding plant species composition. Rural sites had the highest number of plant species. Shannon-Weaver values regarding the plant diversity supported the plant species composition data indicating higher plant diversity in the rural areas, followed by the sub-urban and the urban areas. Plant structural data indicated that forbs were most numerous in the rural sites, and less so in the urban sites. Higher average aerobic heterotrophic bacterial levels were present in the urban soil samples. The bacterial levels were lower in the sub-urban and rural soil samples. Subsequent identification of the dominant bacteria in the soil samples revealed organisms of the genus Bacillus dominated the aerobic heterotrophic bacterial communities in the soil samples. Bacillus species dominated the soil samples along the urbanization gradient. Shannon-Weaver indices based on culture-dependent methods indicated that urban sites had the highest biodiversity. These results could have been exaggerated, because of an overestimation of the number of bacterial morphotypes present in samples. Fungal levels were higher in the soil from samples collected at the rural samples sites. The culture-independent method (DGGE) was not optimized and inconclusive results were obtained. Enzyme assays revealed that potential dehydrogenase, β-glucosidase and urease activity followed a trend along the urbanization gradient, with urban samples registering the highest values and rural sites the lowest. Enzymes involved in carbohydrate catabolism (β-glucosidase and dehydrogenase) registered significantly higher potential activity in urban sites than the sub-urban and rural sites. The results could indicate that urban sites have the potential to lose carbon at higher rates than the rural sites. This aspect may need further investigation. Higher potential urease activity could indicate higher N-cycling in the urban soil environment. Ordination results for soil-, plant- and microbial diversity as well as microbial functionality indicated certain trends along the urbanization gradient. Plant species composition and structure data indicated that urbanization has a definite effect on the plant communities in the urban ecosystem. Results regarding aerobic heterotrophic bacteria populations and potential enzyme activity of the dehydrogenase, β-glucosidase (both active in the carbon cycle) and urease (active in the nitrogen cycle) illustrated clear trends along the urbanization gradient. In conclusion, results indicated that urbanization has an effect on plant species composition, and the population and function of aerobic heterotrophic bacteria and the fungal population. Furthermore, this study demonstrated the potential of using microbial diversity and activity as tools to investigate carbon utilization and storage along an urban-rural gradient. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2011

4 pp. / This is part of a series of publications on climate change and forests/woodlands / Climate change may have dramatic effects on Arizona's forests and woodlands. Wildfires and insects may become of greater concern. Plant species will likely shift in elevation to adapt to the warming conditions.

New farming needs and innovations have, over time, led to changes in land use. Arable fields have been turned into pastures and semi-natural pastures into arable fields. Due to the ecological value of continually grazed semi-natural pastures in Sweden the aim of this study is to find out how former arable fields that are permanently grazed differ from semi-natural pastures. In this study I selected appropriate semi-natural pastures from a national monitoring program on seminatural- pastures and meadows. Plots continuously grazed were compared with grazed plots on former arable fields. Pair-wise differences in the Ellenberg indicator values Light (L), Soil moisture (F), soil pH (R) and soil nitrogen (N), vertical coverage of trees, bushes and vegetation, species richness and species composition were tested. Except for species composition there were only small differences between former arable fields that are permanently grazed and semi-natural pastures. That means former arable fields can with time and grazing gain many of the values continuously grazed semi-natural pastures have.

Bear Lake, a large oligotrophic lake (282 km2), was studied from October 1986 to December 1987 to determine the temporal changes in the zooplankton assemblage at one site in the pelagic zone and one in the littoral area. In this study, species composition, abundance, biomass, and size frequency distribution were determined. Additionally, chlorophyll a, water transparency, and temperature and oxygen profiles were measured to help interpret zooplankton changes during the study. The zooplankton species assemblage comprised eight species of cladocera, seven species of copepods, and five species of rotifers. The abundance and biomass of the zooplankton assemblage, particularly that of crustaceans, were very low and comparable with those of oligotrophic systems. Mean densities of crustaceans in the pelagic zone, excluding copepod nauplii, varied from 250 to 1,700 organisms/m3. The analysis of the size structure of the zooplankton indicated the dominance of small organisms and the scarcity of large organisms, particularly cladocera. The zooplankton assemblage in the littoral zone was similar in species composition, abundance, and size structure to that in the pelagic zone. Many results suggest the littoral zooplankton assemblage is an extension of the pelagic assemblage. Low zooplankton food resources and interference of calcium carbonate particles in the feeding behavior of crustaceans are suggested as the primary factors controlling the low abundance and biomass of zooplankton in Bear Lake. Size-selective fish predation probably causes the assemblage to be dominated by small species. The analysis of Epischura nevadensis, the dominant species in the system, indicated that this species is bivoltine in Bear Lake. In the spring and summer, adult E. nevadensis were more abundant in the littoral zone, whereas copepodites were more abundant offshore. The low density, biomass, and small size structure of the zooplankton in Bear Lake limits its importance as a source of food for fishes.

Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2007.

The structural integrity of fire-dependent ecosystems, such as ponderosa pine (<i>Pinus ponderosa </i> Dougl.) and Interior Douglas-fir (<i>Pseudotsuga menziesii </i> (Mirb.) Franco) biogeoclimatic zones in Interior British Columbia (BC) is changing. The problems within these ecosystems include decreased rangeland area, reduced carrying capacity and loss of biodiversity due to tree encroachment and forest ingrowth caused mainly by fire suppression. The goal of this study was to determine the effect of burning and thinning on understory vegetation of grassland and forested sites. The burning experiment took place at Dew Drop (Tranquille Ecological Reserve) located 20 km northwest of Kamloops, BC. Thinning was done at two upper grassland sites near Cache Creek, BC; Coal Mine Pasture and Gladys Lake Pasture. Species evenness and values of the Shannon-Weiner Diversity Index (H) were reduced (13 and 27%, respectively) within three years following burning (P = 0.014 and P = 0.038, respectively). Burning reduced canopy cover of shrubs on grassland sites (P = 0.005) and it reduced graminoid cover on forest sites (P = 0.014) immediately after the treatment (1999) but both functional groups had recovered by 2002. Litter depth and total canopy cover of plants were reduced in grasslands and forests immediately following burning (1999) but litter depth and canopy cover had recovered by 2002. Litter cover and litter depth beneath the tree canopy were reduced by burning (P = 0.037 and P = 0.009, respectively). Trends in the data indicate forb standing crop increased and total understory standing crop increased following burning in the grassland compared to the control. Graminoid standing crop was reduced 47% by burning in the forests (P = 0.049). Thinning reduced species richness in the first (P = 0.033) and fourth (P = 0.030) years, and H in the first year (P = 0.037) following the thinning at Coal Mine Pasture. Trends in the data suggest understory standing crop increased at Coal Mine and Gladys Lake Pastures following thinning. At both locations, thinning reduced litter depth. Therefore, burning and thinning kills trees, reduces fuel loads, and increases standing crop of the understory.

The structural integrity of fire-dependent ecosystems, such as ponderosa pine (<i>Pinus ponderosa </i> Dougl.) and Interior Douglas-fir (<i>Pseudotsuga menziesii </i> (Mirb.) Franco) biogeoclimatic zones in Interior British Columbia (BC) is changing. The problems within these ecosystems include decreased rangeland area, reduced carrying capacity and loss of biodiversity due to tree encroachment and forest ingrowth caused mainly by fire suppression. The goal of this study was to determine the effect of burning and thinning on understory vegetation of grassland and forested sites. The burning experiment took place at Dew Drop (Tranquille Ecological Reserve) located 20 km northwest of Kamloops, BC. Thinning was done at two upper grassland sites near Cache Creek, BC; Coal Mine Pasture and Gladys Lake Pasture. Species evenness and values of the Shannon-Weiner Diversity Index (H) were reduced (13 and 27%, respectively) within three years following burning (P = 0.014 and P = 0.038, respectively). Burning reduced canopy cover of shrubs on grassland sites (P = 0.005) and it reduced graminoid cover on forest sites (P = 0.014) immediately after the treatment (1999) but both functional groups had recovered by 2002. Litter depth and total canopy cover of plants were reduced in grasslands and forests immediately following burning (1999) but litter depth and canopy cover had recovered by 2002. Litter cover and litter depth beneath the tree canopy were reduced by burning (P = 0.037 and P = 0.009, respectively). Trends in the data indicate forb standing crop increased and total understory standing crop increased following burning in the grassland compared to the control. Graminoid standing crop was reduced 47% by burning in the forests (P = 0.049). Thinning reduced species richness in the first (P = 0.033) and fourth (P = 0.030) years, and H in the first year (P = 0.037) following the thinning at Coal Mine Pasture. Trends in the data suggest understory standing crop increased at Coal Mine and Gladys Lake Pastures following thinning. At both locations, thinning reduced litter depth. Therefore, burning and thinning kills trees, reduces fuel loads, and increases standing crop of the understory.

The concept of habitat quality is fundamental to the study of ecology, and ecologists have long recognized the importance of vegetation structure and composition in the assessment of wildlife habitat. Vegetative characteristics affect productivity in birds for a variety of reasons (e.g., predator assemblages, nesting sites, song perches, food availability). I investigated the relationship between habitat quality and prey availability and the effect these parameters have on reproductive success in golden-cheeked warblers (Dendroica chrysoparia). My objectives were to 1) determine any differences in pairing and fledging success of warbler territories within two ecosites exhibiting two distinctive tree species composition 2) explore the relationship between tree species composition, arthropod density, and foraging effort, and the effect these parameters have on reproductive success in golden-cheeked warblers and 3) investigate the connection between preferred foraging substrates and changes in arthropod abundance within golden-cheeked warbler territories throughout the breeding season. I mapped individual warbler territories and searched for fledglings, observed foraging behavior, and collected arthropods in each territory to determine productivity, foraging effort, and food availability. I conducted these methods over two seasons in juniper-oak woodlands on Fort Hood, north-central Texas within 347 territories of two vegetative types: those marked by the predominance of post oak (Quercus stellata) and those marked by the predominance of Texas oak (Quercus buckleyi). Pairing and fledging success of territories differed substantially between the two vegetative types. Movement rates differed considerably between the two vegetative types, indicating a difference in prey encounter rate. Foraging data indicated a clear switch in preferred foraging substrates from oak species early in the breeding season, to Ashe juniper (Juniperus ashei) in mid-May. Arthropod sampling revealed a correlation between preferred foraging substrates and arthropod density. Results suggested that Texas oak was an important foraging substrate for golden-cheeked warblers, and territories that lack this tree species generally did not succeed in fledging young. My study can be used to indicate areas that should be targeted for conservation by local, state, and federal government because they provide high quality habitat based on warbler productivity.

In the pursuit of sustainable development, Environmental Impact Assessments (EIA) are acknowledged globally as a tool designed to assist governing authorities by providing the information required to make an informed decision regarding development proposals. South Africa has entrenched this EIA requirement in the presiding environmental legislation: the National Environmental Management Act (Act 107 of 1 998). In the effort to manage the negative impact of development on the rocky ridges of Johannesburg, the Gauteng Department of Agriculture, conservation, Environment and Land Affairs (GDACEL) has introduced a buffer zone requirement in the procedure of the EIA. The Red Data Plant Policy for Environmental Impact Evaluations for GDACEL described a buffer zone as a collar of land that filters out inappropriate influences from surrounding activities. As a tool in the EIA, a buffer zone is a worthwhile concept. However, the determination of the dimension of the buffer zone on rocky ridges, is non-discriminatory between sites, and thus, presents potential contention between decision-making authorities and developers. There is a need for further research to establish a scientifically acceptable method of determining site-specific buffer zones for individual EIA applications. The key objective of this paper is to suggest the possibility of determining a buffer zone that accommodates the unique environmental aspects of each site. This is achieved by determining the distance between the edge of existing developments and the point at which the successional climax community within the adjacent natural vegetation is established. Three suitable study sites, consisting of developed residential estates on ridges adjacent to nature reserves, were identified within the greater Johannesburg metropolis. The three study sites identified for this assessment include Kloofendal (west), Morning Hill (east) and Kliprivier (south). Within each study site field surveys were conducted along transects starting 5m from the development edge and ending 75m within the nature reserve adjacent to each site. Quantitative (species density) and qualitative (Braun-Blanquet cover-abundance values) data analysis was employed to describe and evaluate the identified plant communities. The data in this study provides clear indication that a 25-35m buffer zone would suffice for these specific plant communities to maintain a climax successional status if impacted on by residential development. This paper thus makes a case for permitting the determining of variable buffers zones, based on a gradient analysis of a plant community, as a potential panacea to the problem of resistance and reluctance to accept present standard buffer zones. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2007.

In the pursuit of sustainable development, Environmental Impact Assessments (EIA) are acknowledged globally as a tool designed to assist governing authorities by providing the information required to make an informed decision regarding development proposals. South Africa has entrenched this EIA requirement in the presiding environmental legislation: the National Environmental Management Act (Act 107 of 1 998). In the effort to manage the negative impact of development on the rocky ridges of Johannesburg, the Gauteng Department of Agriculture, conservation, Environment and Land Affairs (GDACEL) has introduced a buffer zone requirement in the procedure of the EIA. The Red Data Plant Policy for Environmental Impact Evaluations for GDACEL described a buffer zone as a collar of land that filters out inappropriate influences from surrounding activities. As a tool in the EIA, a buffer zone is a worthwhile concept. However, the determination of the dimension of the buffer zone on rocky ridges, is non-discriminatory between sites, and thus, presents potential contention between decision-making authorities and developers. There is a need for further research to establish a scientifically acceptable method of determining site-specific buffer zones for individual EIA applications. The key objective of this paper is to suggest the possibility of determining a buffer zone that accommodates the unique environmental aspects of each site. This is achieved by determining the distance between the edge of existing developments and the point at which the successional climax community within the adjacent natural vegetation is established. Three suitable study sites, consisting of developed residential estates on ridges adjacent to nature reserves, were identified within the greater Johannesburg metropolis. The three study sites identified for this assessment include Kloofendal (west), Morning Hill (east) and Kliprivier (south). Within each study site field surveys were conducted along transects starting 5m from the development edge and ending 75m within the nature reserve adjacent to each site. Quantitative (species density) and qualitative (Braun-Blanquet cover-abundance values) data analysis was employed to describe and evaluate the identified plant communities. The data in this study provides clear indication that a 25-35m buffer zone would suffice for these specific plant communities to maintain a climax successional status if impacted on by residential development. This paper thus makes a case for permitting the determining of variable buffers zones, based on a gradient analysis of a plant community, as a potential panacea to the problem of resistance and reluctance to accept present standard buffer zones. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2007.