Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.

The quality of terrestrial invertebrates as indicators for the detection of ecological change associated with disturbance is widely acknowledged. Invertebrates, at the community level, are often more sensitive to changes than are plants or vertebrates. Both ants and beetles have been studied extensively; changes in ant community composition have been applied successfully as an indication of restoration success. Ants are ideal due to their high abundances and diversity, their ecological importance at all trophic levels, their relative sampling and sorting ease and their sensitivity to ecological change. A detailed understanding of community dynamics greatly facilitates the correct interpretation of signals provided by indicator taxa. Beetles to a great extent, are useful ecological or biodiversity indicators and have been adopted as suitable indicators in environmental monitoring and assessment, as well as to facilitate the evaluation of conservation of biodiversity in landscapes subjected to harvesting. It is well known that ground-dwelling beetle assemblages (especially ground and rove beetles) are sensitive to habitat structure, microclimate and biodiversity management strategies. The use of bio-indicators with regard to land management is becoming increasingly common in ecological studies, because the results obtained can hopefully provide a framework of reference for the prediction of ecosystem response and the means to select the best land use practices. Such predictions will become useful when considering the consequences of ecological perturbations such as fire regimes, bush encroachment, grazing, mining activity, etc. The objectives of this particular study are to determine the effect that past fire treatments may have had on vegetation structure and how ant and beetle assemblages respond to such changes, and what such changes in habitat structure mean in terms of increased bush density. It is expected that the results obtained will provide an indication of the manner in which ecosystem change affects bio-indicator community assemblages, and how this can be applied with regard to future restoration efforts. These organisms were sampled by means of pitfall traps placed within strategic sites varying in vegetation composition and sampled over a number of days. The content of each trap was sorted to genus level, and where possible, to species level and their application of selected invertebrates as indicators of ecosystem change due to veld fires, species richness, abundance and composition determined. The data obtained was analysed statistically using STATISTICA, CANOCO, PRIMER and Microsoft Excel. Four sites with different burn histories were selected: an unburnt site, one burnt in 2002, one burnt in 1997, and one burnt in 1992. Soil characteristics were found to be relatively homogenous throughout all the sample sites, while each of the burn treatment replicates could be characterised by a particular plant structural arrangement. With regards to the ant assemblages, both in terms of species composition and functional group composition, low species diversity appeared to segregate the 1997 burn treatment replicates markedly from the other three burn treatments, with a high degree of species dominance exhibited by Anaplolepis steingroeveri. The ants seem to indicate higher species diversity in the burn treatment sites that had a more diverse vegetation structure. This occurrence however seems to alter over time after a fire incident, before returning to as close to its original state as possible. The beetles, however, displayed very haphazard assemblages, and did not show any discernable significant results that may be used to describe the environmental parameters in question.The reaction of the ants seemed to occur over an extended period of time, with immediate effects of the burn being an increase in non-specialised and opportunistic species abundances, possibly due to a decrease in competition with other species and taxa. Changes in ant assemblages became more apparent after seven years of the burn incident, seemingly linked to structural changes in the plant community. Ant species diversity increased again at the twelve year recovery time, with and associated change in plant habitat structure. The ants thus, in conclusion, show significant results towards indicating a response to habitat change brought on by fire. It is a requirement that this experiment be replicated in order to establish more discernable patterns. Additional recommendations to improve on this study are also discussed. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.

The quality of terrestrial invertebrates as indicators for the detection of ecological change associated with disturbance is widely acknowledged. Invertebrates, at the community level, are often more sensitive to changes than are plants or vertebrates. Both ants and beetles have been studied extensively; changes in ant community composition have been applied successfully as an indication of restoration success. Ants are ideal due to their high abundances and diversity, their ecological importance at all trophic levels, their relative sampling and sorting ease and their sensitivity to ecological change. A detailed understanding of community dynamics greatly facilitates the correct interpretation of signals provided by indicator taxa. Beetles to a great extent, are useful ecological or biodiversity indicators and have been adopted as suitable indicators in environmental monitoring and assessment, as well as to facilitate the evaluation of conservation of biodiversity in landscapes subjected to harvesting. It is well known that ground-dwelling beetle assemblages (especially ground and rove beetles) are sensitive to habitat structure, microclimate and biodiversity management strategies. The use of bio-indicators with regard to land management is becoming increasingly common in ecological studies, because the results obtained can hopefully provide a framework of reference for the prediction of ecosystem response and the means to select the best land use practices. Such predictions will become useful when considering the consequences of ecological perturbations such as fire regimes, bush encroachment, grazing, mining activity, etc. The objectives of this particular study are to determine the effect that past fire treatments may have had on vegetation structure and how ant and beetle assemblages respond to such changes, and what such changes in habitat structure mean in terms of increased bush density. It is expected that the results obtained will provide an indication of the manner in which ecosystem change affects bio-indicator community assemblages, and how this can be applied with regard to future restoration efforts. These organisms were sampled by means of pitfall traps placed within strategic sites varying in vegetation composition and sampled over a number of days. The content of each trap was sorted to genus level, and where possible, to species level and their application of selected invertebrates as indicators of ecosystem change due to veld fires, species richness, abundance and composition determined. The data obtained was analysed statistically using STATISTICA, CANOCO, PRIMER and Microsoft Excel. Four sites with different burn histories were selected: an unburnt site, one burnt in 2002, one burnt in 1997, and one burnt in 1992. Soil characteristics were found to be relatively homogenous throughout all the sample sites, while each of the burn treatment replicates could be characterised by a particular plant structural arrangement. With regards to the ant assemblages, both in terms of species composition and functional group composition, low species diversity appeared to segregate the 1997 burn treatment replicates markedly from the other three burn treatments, with a high degree of species dominance exhibited by Anaplolepis steingroeveri. The ants seem to indicate higher species diversity in the burn treatment sites that had a more diverse vegetation structure. This occurrence however seems to alter over time after a fire incident, before returning to as close to its original state as possible. The beetles, however, displayed very haphazard assemblages, and did not show any discernable significant results that may be used to describe the environmental parameters in question.The reaction of the ants seemed to occur over an extended period of time, with immediate effects of the burn being an increase in non-specialised and opportunistic species abundances, possibly due to a decrease in competition with other species and taxa. Changes in ant assemblages became more apparent after seven years of the burn incident, seemingly linked to structural changes in the plant community. Ant species diversity increased again at the twelve year recovery time, with and associated change in plant habitat structure. The ants thus, in conclusion, show significant results towards indicating a response to habitat change brought on by fire. It is a requirement that this experiment be replicated in order to establish more discernable patterns. Additional recommendations to improve on this study are also discussed. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.

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Made available in DSpace on 2014-08-20T13:44:25Z (GMT). No. of bitstreams: 1 dissertacao_leandro_jose_de_oliveira_von_hausen.pdf: 333411 bytes, checksum: 4bfffa1710e89ebccdacd709fe323cf5 (MD5) Previous issue date: 2012-04-04 / The irrigated rice (Oryza sativa L.) farming success it is directly related to the high quality seed production. The seed is an extremely important input, because the maximum potential of agricultural productivity is defined by its genetic pattern, so that all the other resources are explored and handled in function of that. The objective of this research was to evaluate the physiologic and physical quality of the seed produced in the main stems and in the irrigated rice tillers in different cultivatars and submitted to different agricultural practices. The experiment was accomplished in 2008/2009, at Experimental Station of Terras Baixas, Embrapa, located in Capão do Leão County RS.Itt was evaluated the cultivars: BRS Querência, BRS Firmeza, BRS Pelota and BRS Atalanta. The physiological quality was evaluated through the germination and vigor tests, besides, it was measured the weight of a thousand seeds and the whole grains income. It was tested the effects caused by the irrigation handling, chemical products treatments and plant structure factors where it were picked the seeds. The data were analyzed by the SAS statistical program (2001). In the seeds physiological quality it was verified that the germination was smaller in seeds produced by tillers in BRS Pelota cultivate. Otherwise, the hydric and chemist handle factors influenced this variable in BRS Atalanta and BRS Firmeza cultivars. Regarding the vigor just the hydric and chemist handlings influenced it in BRS Querência and BRS Atalanta cultivates. The main stem and affiliates seeds were different for the variable of a thousand seeds weight just to BRS Querência cultivar in chemicals absence and water laminates suppression. In BRS Firmeza cultivar this variable was influenced by the agricultural practices, while in BRS Atalanta and BRS Pelota cultivars they were only influenced by the chemical handling. The whole grains income was different between main stem and its tillers in BRS Atalanta in chemical absence and water laminates suppression. In BRS Querência and BRS Firmeza cultivars this variable was influenced by the agricultural practices, while to BRS Pelota cultivar it was only influenced by the chemical handling. / O sucesso das lavouras de arroz irrigado (Oryza sativa L.) está diretamente relacionado à produção de sementes de alta qualidade. A semente é um insumo extremamente importante, pois o potencial máximo de produtividade agrícola é definido pelo seu padrão genético, de modo que todos os demais recursos sejam explorados e manejados em função dela. O objetivo dessa pesquisa foi avaliar a qualidade fisiológica e física das sementes produzidas nos colmos principais e nos perfilhos de arroz irrigado em diferentes cultivares e submetidas a diferentes práticas agrícolas. O experimento foi realizado na safra 2008/2009, na Estação Experimental de Terras Baixas, da Embrapa Clima Temperado, localizada no município de Capão do Leão RS. Foi avaliado as cultivares: BRS Querência, BRS Firmeza, BRS Pelota e BRS Atalanta. A qualidade fisiológica das sementes foi avaliada através dos testes de germinação e vigor, além disso, foi determinado o peso de mil sementes e o rendimento de grãos inteiros. Foram testados os efeitos dos fatores manejo da irrigação, tratamentos com produtos químicos e estrutura da planta onde foram colhidas as sementes. Os dados foram analisados pelo programa estatístico SAS (2001). Na qualidade fisiológica das sementes verificou-se que a germinação foi menor nas sementes produzidas pelos perfilhos na cultivar BRS Pelota. Enquanto que, os fatores manejo hídrico e químico influenciaram esta variável nas cultivares BRS Atalanta e BRS Firmeza. Com relação ao vigor apenas os manejos hídrico e químico influenciaram-o nas cultivares BRS Querência e BRS Atalanta. As sementes do colmo principal e perfilhos foram diferentes para a variável de peso de mil sementes apenas para a cultivar BRS Querência na ausência de químico e supressão da lamina d água. Na cultivar BRS Firmeza esta variável foi influenciada pelas práticas agrícolas, enquanto que as cultivares BRS Atalanta e BRS Pelota somente foram influenciadas pelo manejo químico. O rendimento de grãos inteiros foi diferente entre colmo principal e perfilhos na BRS Atalanta na ausência de químico e supressão da lamina d água. Na cultivar BRS Querência e BRS Firmeza esta variável foi influenciada pelas práticas agrícolas, enquanto que a cultivar BRS Pelota somente foi influenciada pelo manejo químico.