Gold mine tailings material facilities are characterized by sparse vegetation and an abundance of dust. Mine tailings facilities are examples of extreme geotechnical and geochemical conditions which make it almost impossible for higher plants to establish and grow without rehabilitation intervention. In most cases higher plants such as grasses and trees are the focus areas for rehabilitation, but, having a look at something a little smaller such as biological crusts, it is seen that these micro-organisms play very important roles in any ecosystem. Various studies have shown that biological crusts, consisting of micro-organisms such as lichens, algae and cyanoprokaryotes enhance the soil quality by binding soil particles together, forming aggregates which counteract the erosive forces of wind and water. They play a part in nitrogen and carbon fixation, increase the soil surface temperature and increase the water retention of the soil. Thus, these organisms improve the overall health of the soil, which will in time encourage the successful establishment of higher plants. The aim of this study was to investigate the presence of cyanoprokaryotes and soil algae on mine tailings storage facilities that have been rehabilitated for different periods of time as well as to correlate the presence of these species with the physical and chemical characteristics of the mine tailings material. Chemical, physical and biological analyses of soil samples were done. Some of the ecologically important and dominant species were isolated and protocols were developed in order to identify the most successful manner in which to re-inoculate the organisms to a chosen substrate and how to measure biomass. Due to the immense cost of standard rehabilitation practices there is a need for a more cost effective, sustainable manner in which to protect the tailings material against the erosive forces of wind and water with as little input as possible. The influence of an organism cultured in normal Bold’s Basal medium (BBM) growth medium, BBM growth medium with half the phosphate concentration and BBM growth medium with half the nitrate concentration on the establishment of a biological soil crust (BSC) was tested. To test the influence of the inoculums already present in the tailings material and in the air, trials with mulch, water and nutrients without the addition of an organism was also investigated. This was done in the controlled environment of a glasshouse, as well as in field conditions. The biomass of the cyanoprokaryotes and algae, as well as the soil surface strength was also tested. The results show that the time of rehabilitation did not have an influence on the cyanoprokaryotes as well as algal species that occurred on the tailings material. Chlorella sp., Chlorococcum sp. and Klebsormidium sp. were present on all six sites, except on the fresh material and 15 year old material where no rehabilitation has been done. As for dominance; Chlamydomonas sp., Chlorococcum sp., Klebsormidium sp. and Phormidium sp. were dominant on all six sites except for the fresh material, where nothing grew. An array of methods exists for measuring algal biomass as a measure of growth. During the development of protocols for further use in investigating the growth of algae, the extraction solvent ethanol, for use in chlorophyll a extraction, was identified as the most sufficient. The re-inoculation of cyanoprokaryotes and soil algae onto a chosen substrate is most successful when pouring the organisms, cultured in growth medium and 0.1% agar, over the substrate. During the glasshouse trials the influence of the growth medium and growth medium with half the nitrate and half the phosphate concentrations showed that Chlamydomonas sp. produced the highest biomass when cultured in BBM. With Nostoc sp. the highest biomass occurred with culturing in BBM and BBM with half the phosphate concentration. Microcoleus vaginatus showed no significant difference when cultured in the three different growth mediums (BBM, BBM with half the nitrate concentration and BBM with half the phosphate concentration). Overall Nostoc sp. produced the highest biomass (34.33 μg/g), followed by Microcoleus vaginatus (17.05 μg/g) and Chlamydomonas sp. (6.12 μg/g). Soil surface strength, measured with a hand held penetrometer showed that Chlamydomonas sp. cultured in BBM growth medium produced the most stable crust (2.58 kg/cm2), although it had the lowest biomass measurements (6.12 μg/g). Nostoc sp. produced the highest biomass (34.44 μg/g), but had the lowest soil surface strength results (1.75 kg/cm2). Microcoleus vaginatus proved to be the species with high biomass production (17.05 μg/g), as well as high soil surface strength (2.08 kg/cm2). M. vaginatus is also a pioneer species and is therefore a good choice as primary inoculum on bare tailings material. It was decided to use Nostoc sp. in the field trials due to its high biomass and Microcoleus vaginatus due to the high soil surface strength produced. Despite the occurrence of a severe thunder storm on the afternoon of application and poor water management during the field trials the significance of water on the establishment of soil algae and cyanoprokaryotes on tailings material was determined. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Gold mine tailings material facilities are characterized by sparse vegetation and an abundance of dust. Mine tailings facilities are examples of extreme geotechnical and geochemical conditions which make it almost impossible for higher plants to establish and grow without rehabilitation intervention. In most cases higher plants such as grasses and trees are the focus areas for rehabilitation, but, having a look at something a little smaller such as biological crusts, it is seen that these micro-organisms play very important roles in any ecosystem. Various studies have shown that biological crusts, consisting of micro-organisms such as lichens, algae and cyanoprokaryotes enhance the soil quality by binding soil particles together, forming aggregates which counteract the erosive forces of wind and water. They play a part in nitrogen and carbon fixation, increase the soil surface temperature and increase the water retention of the soil. Thus, these organisms improve the overall health of the soil, which will in time encourage the successful establishment of higher plants. The aim of this study was to investigate the presence of cyanoprokaryotes and soil algae on mine tailings storage facilities that have been rehabilitated for different periods of time as well as to correlate the presence of these species with the physical and chemical characteristics of the mine tailings material. Chemical, physical and biological analyses of soil samples were done. Some of the ecologically important and dominant species were isolated and protocols were developed in order to identify the most successful manner in which to re-inoculate the organisms to a chosen substrate and how to measure biomass. Due to the immense cost of standard rehabilitation practices there is a need for a more cost effective, sustainable manner in which to protect the tailings material against the erosive forces of wind and water with as little input as possible. The influence of an organism cultured in normal Bold’s Basal medium (BBM) growth medium, BBM growth medium with half the phosphate concentration and BBM growth medium with half the nitrate concentration on the establishment of a biological soil crust (BSC) was tested. To test the influence of the inoculums already present in the tailings material and in the air, trials with mulch, water and nutrients without the addition of an organism was also investigated. This was done in the controlled environment of a glasshouse, as well as in field conditions. The biomass of the cyanoprokaryotes and algae, as well as the soil surface strength was also tested. The results show that the time of rehabilitation did not have an influence on the cyanoprokaryotes as well as algal species that occurred on the tailings material. Chlorella sp., Chlorococcum sp. and Klebsormidium sp. were present on all six sites, except on the fresh material and 15 year old material where no rehabilitation has been done. As for dominance; Chlamydomonas sp., Chlorococcum sp., Klebsormidium sp. and Phormidium sp. were dominant on all six sites except for the fresh material, where nothing grew. An array of methods exists for measuring algal biomass as a measure of growth. During the development of protocols for further use in investigating the growth of algae, the extraction solvent ethanol, for use in chlorophyll a extraction, was identified as the most sufficient. The re-inoculation of cyanoprokaryotes and soil algae onto a chosen substrate is most successful when pouring the organisms, cultured in growth medium and 0.1% agar, over the substrate. During the glasshouse trials the influence of the growth medium and growth medium with half the nitrate and half the phosphate concentrations showed that Chlamydomonas sp. produced the highest biomass when cultured in BBM. With Nostoc sp. the highest biomass occurred with culturing in BBM and BBM with half the phosphate concentration. Microcoleus vaginatus showed no significant difference when cultured in the three different growth mediums (BBM, BBM with half the nitrate concentration and BBM with half the phosphate concentration). Overall Nostoc sp. produced the highest biomass (34.33 μg/g), followed by Microcoleus vaginatus (17.05 μg/g) and Chlamydomonas sp. (6.12 μg/g). Soil surface strength, measured with a hand held penetrometer showed that Chlamydomonas sp. cultured in BBM growth medium produced the most stable crust (2.58 kg/cm2), although it had the lowest biomass measurements (6.12 μg/g). Nostoc sp. produced the highest biomass (34.44 μg/g), but had the lowest soil surface strength results (1.75 kg/cm2). Microcoleus vaginatus proved to be the species with high biomass production (17.05 μg/g), as well as high soil surface strength (2.08 kg/cm2). M. vaginatus is also a pioneer species and is therefore a good choice as primary inoculum on bare tailings material. It was decided to use Nostoc sp. in the field trials due to its high biomass and Microcoleus vaginatus due to the high soil surface strength produced. Despite the occurrence of a severe thunder storm on the afternoon of application and poor water management during the field trials the significance of water on the establishment of soil algae and cyanoprokaryotes on tailings material was determined. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Mikrobielle Gemeinschaften werden direkt und indirekt von einem komplexen System verschiedenster Interaktionen zwischen biotischen und abiotischen Faktoren beeinflusst. So zum Beispiel von verschiedenen Pflanzenarten und ihren jeweiligen Eigenschaften, dem Nährstoffgehalt des Bodens, sowie dem pH-Wert. Im Gegenzug gestalten Mikroorganismen als wichtige Treiber der C- und N-Kreisläufe ihre Umwelt. Im Rahmen der vorliegenden Arbeit wurden mehrere Studien unter kontrollierten Feld- und Laborbedingungen, sowie unter natürlichen Bedingungen im Freiland durchgeführt, um verschiedene Einflussfaktoren zu bestimmen und den Grad ihres Einflusses zu ermitteln. Die Zusammensetzung der prokaryotischen Gemeinschaften in den verschiedenen Bodenproben wurden mit Hilfe phylogenetischer Marker, der 16S-rRNA Gene und der 16S-rRNA, analysiert. Die erhaltenen Amplikon-basierten Daten wurden dann prozessiert und die Indices für Artenvielfalt und Artenreichtum berechnet. Zusätzlich wurden Betadiversitätsanalysen durchgeführt, um Unterschiede in der Zusammensetzung der bakteriellen Gemeinschaft zwischen den verschiedenen Behandlungen sichtbar zu machen. Des Weiteren wurden die erhaltenen DGGE Profile für Clusteranalysen verwendet, um Ähnlichkeiten oder Unterschiede in der Struktur der Bakteriengemeinschaft zwischen den verschiedenen Behandlungen aufzuzeigen. Die vorliegende Arbeit gibt einen Einblick über den Einfluss der Baumarten, Baumartendiversität, des Laubes und des Probennahmezeitpunktes auf die Zusammensetzung und Diversität von Bakteriengemeinschaften in Böden. Die erhaltenen Daten zeigten, dass die Laubschicht der Haupteinflussfaktor auf die Zusammensetzung der bakteriellen Gemeinschaft in der Rhizosphäre von jungen Buchen und Eschen ist. Des Weiteren zeigte sich, das verschiedene Baumarten, deren Diversität, sowie saisonale Unterschiede nur einen geringen Einfluss auf die Struktur der bakteriellen Gemeinschaft haben. Zusätzlich konnte gezeigt werden, dass die mikrobielle Gemeinschaftsstruktur nicht signifikant von Buchen- und Eschensetzlingen beeinflusst wird, vermutlich aufgrund des frühen Entwicklungsstadiums der verwendeten Baumsetzlinge. Weiterhin konnte gezeigt werden, dass die Buchensetzlinge das Wachstum von Bakterien inhibierten, während das Pilzwachstum gefördert wurde. Dies wurde vermutlich hervorgerufen durch eine Verschiebung des pH-Wertes im Boden verursacht durch buchenspezifische Wurzelausscheidungen. Morphologisch unterschiedliche Baumarten beeinflussen die Struktur und Diversität mikrobieller Gemeinschaften auf verschiedenen Wegen. Die Analyse der Bakterien- und Pilzgemeinschaften in natürlichen Waldböden unter erwachsenen Buchen und Fichten zeigte einen signifikanten Einfluss der untersuchten Baumarten auf deren Zusammensetzung. Es konnte ein Einfluss des pH-Werts auf die Bakterien- und Pilzvielfalt unter den analysierten Fichtenbeständen gezeigt werden. Des Weiteren wurden die Auswirkungen hoher NO3- Depositionen auf die CH4 und N2O Gasflüsse und die aktiven Bakterien- und Archeengemeinschaften in gemäßigten Laubwaldböden mit Hilfe von Mesokosmen untersucht. Es konnte ein starker Effekt der NO3- Düngung auf die CH4 Aufnahmeraten und N2O Emissionen des gedüngten Laubwaldbodens gezeigt werden. Die N-Düngung hemmte die CH4 Aufnahme des Bodens, während die N2O Emission stieg. Die Bakteriengemeinschaft in den gedüngten Mikrokosmen verschob sich im Verlauf des Versuches in Richtung einer denitrifizierenden Gemeinschaft, dominiert durch die Gattung Rhodanobacter. Darüber hinaus konnte eine Reduzierung der bakteriellen Vielfalt und der CO2 Emission innerhalb der N-gedüngten Mikrokosmen gezeigt werden. Des Weiteren sanken die CO2 Emissionsraten in beiden Behandlungen im Verlauf des Experiments. Dies deutet auf eine reduzierte Aktivität der vorhandenen Bodenmikroorganismen hin, möglicherweise hervorgerufen durch eine C Limitierung des verwendeten Waldbodens. Obwohl eine Verschiebung in der relativen Häufigkeit der auftretenden nitrifizierenden Archeen der Gattung Nitrosotalea nachgewiesen wurde, konnte eine signifikante Veränderung in der Zusammensetzung der gesamten Archeengemeinschaft nicht beobachtet werden. Die Ergebnisse zeigten jedoch einen erheblichen Beitrag methylotropher, methanotropher und nitrifizierender Bakterien, welche in geringer Zahl auftraten, in Bezug auf die gemessene CH4 Aufnahme. Des Weiteren wurden die Auswirkungen der Anwesenheit von Ameisen und ihrer Aktivitäten auf die Aktivität und Vielfalt der mikrobiellen Gemeinschaften im Boden und Ameisennest untersucht. Ameisen transportierten den von Läusen gewonnenen Honigtau in den Boden und verursachten damit eine Abnahme der mikrobiellen Biomasse in der Streuschicht, während die δ15N-Signatur, die basale Atmung und die mikrobielle Biomasse im Boden erhöht wurden. Im Gegensatz dazu konnten mittels Cluster-Analyse der erstellten DGGE Profile keine deutlichen Unterschiede der mikrobiellen Gemeinschaftsstruktur in den untersuchten Mikrokosmen gezeigt werden. Im Gegensatz dazu beeinflusste die Nestbauaktivität und der Eintrag von organischen Substanzen in den Boden durch die Ameisen jedoch die Struktur der Bakteriengemeinschaften im Freiland. Die Cluster-Analyse der erhaltenen DGGE Profile zeigte Unterschiede in der Zusammensetzung der bakteriellen Gemeinschaft in Abhängigkeit vom Probenentnahmeort und der Ameisenaktivität. Außerdem konnte gezeigt werden, dass sich die Struktur der Bakteriengemeinschaft in den Ameisennestern von der im Umgebungsboden unterschied. Ein sekundäres Projekt dieser Arbeit war die Erfassung und der Vergleich der mikrobiellen Gemeinschaften in biologischen Bodenkrusten zweier unterschiedlicher Standorte in extrazonalen, trockenen Bergsteppen der nördlichen Mongolei. Die Studie zeigte deutliche Unterschiede in der mikrobiellen Gemeinschaftsstruktur der beiden Standorte, welche sich im Grad der Störung unterschieden.

This thesis considers various aspects of the use of ground-based methods and remote sensing of Biological Soil Crusts (BSC). They are mostly distributed in winter rainfall dominated areas such as those at Middleback Field Centre (MFC) in South Australia. They can be used potentially as an indicator of rangeland condition by estimating grazing pressure (trampling). Two BSC based indicators for rangeland condition assessment are species composition and cover. While there is strong agreement that BSC composition is a good indicator, there is less agreement that BSC cover alone is a good indicator. Although BSC have been included in previous remotely-sensed studies, their spectral characteristics, and hence their contributions to remotely-sensed spectral signatures, are not well known. Data collection methods were refined for suitable method selection, stratification and site characterization, and morphological/ functional group classification. Cover data of BSC were collected using a 100 m line-intercept method on the stratified land units and statistical analyses were based on the cover variance analyses. Spectra of BSC groups were collected and characterized for different remote sensing indices. Five grazing gradient models based on collected spectra were developed for the evaluation of BSC effect on remotely-sensed data. Both existing and newly developed remote sensing indices were examined for BSC detection. Sampling for cover of BSC in the field showed that there is indeed a detectable change with distance from water, suggesting that BSC cover can be used as an indicator of rangeland condition, provided that appropriate stratification of the study sites is carried out prior to sampling, and spectral differences in morphological and functional groups are taken into account. Spectral analysis of BSC components showed that different classes of organisms in the crusts have different spectral characteristics, and in particular, that the (commonly-used) perpendicular vegetation index (PD54) is not suitable for detecting BSC. On the other hand, ground-level spectral modelling showed that the Normalized Difference Vegetation Index (NDVI) and Soil Stability Index (SSI) did show a distinguishable contribution from BSC. A procedure for detecting cover of BSC was developed for image taken during the period after an effective rain, in contrast to the normal practice of selecting images of dry surfaces for interpretation. The most suitable intervals appears to be 2-4 days after rain in late autumn, winter and early spring. Of the existing indices, the SSI is the best for estimating cover of BSC from Landsat images. However, eight new indices, specifically designed for detection of BSC were developed during the cource of this work. The best results were obtained for indices using using the middle-infrared bands. These results are promising for application to rangeland monitoring and suggest that BSC cover is an important indicator of rangeland condition if appropriate stratification, classification and data-collection methods are used. The effects of BSC cover on a remotely-sensed method are considerable, and thus they can not be neglected during image interpretation. There are different phenological patterns for BSC, annual and perennial elements, thus there is the possibility for the selection of imagery based on each phenological stage to detect these elements. Application of certain indices such as the PD54 may create mis-estimation of land covers. Although some of the existing and newly developed indices had significant results for BSC cover estimation, there is a requirement for a standalone remotely-sensed method to conclude the best index.

As crostas são o resultado da degradação da estrutura superficial dos solos, favorecem a erosão e a degradação ambiental dos solos. Este estudo avaloiu a dinâmica da formação de crostas superficiais e as consequencias sobre a porosidade, condutividade hidráulica (K), retenção de água, densidade (Ds) e a rugosidade de um Argissolo Vermelho amarelo conduzido com diferentes sistemas de preparo do solo e aplicação de lâminas de chuva simulada. Avaliou-se também, através de um experimento em laboratório, os processos envolvidos na quebra dos agregados, sob chuvas simuladas. O experimento foi conduzido, nos anos de 2009 e 2010. Em parcelas de 15 x 30 m foram conduzidos os diferentes preparos do solo: preparo convencional (PC), preparo reduzido (PR) e sem preparo (SP). Dentro das parcelas instalou-se micro-parcelas de 1m x 1m, onde foram aplicadas diferentes lâminas de chuva simulada (0, 27, 54 e 80 mm) com intensidade de 80 mm h-1. Foram realizadas coletas de dados de rugosidade, medidas de K, coleta de amostras indeformadas de solo para análise da porosidade e confecção de lâminas delgadas, e também anéis cilíndricos para curva de retenção de água (CRA) e Ds do solo. No experimento de laboratório, utilizou-se dois solos (siltoso e argiloso) e duas classe de agregados (1-3 e 3-5 mm). Os agregados foram submetidos a diferentes chuvas simuladas (28mmh-1 + EC forte; 28mmh-1 + EC fraca; 90mmh-1 + EC forte; 90mmh-1 + EC fraca) e após avaliou-se o diâmetro médio ponderado dos agregados (DMP). A dinâmica da formação de crostas ocorreu de maneira diferenciada em ambos os sistemas de preparo. Nos sistemas de PC e PR a maior redução da porosidade, pelo efeito da chuva aplicada, ocorreu na camada da crosta e no sistema SP na camada da subcrosta. A camada da crosta foi responsável pela redução da porosidade e K, e aumento da Ds nos sistemas PC e PR. As maiores umidades volumétricas observadas nas CRA ocorreram no sistema de PR e as menores no PC e não demonstraram evolução entre as chuvas aplicadas. A rugosidade superficial do solo variou em função dos sistemas de preparo realizados. Os sistemas conservacionistas (PR e SP) apresentaram maior rugosidade no primeiro ano, no segundo ano a maior rugosidade foi observada no sistema SP. O PC demonstrou nos dois anos estudados a mesma tendência, em função das chuvas aplicadas, inicialmente ocorreu um aumento na rugosidade até uma chuva máxima diminuindo em seguida. No experimento em laboratório, as maiores reduções no DMP ocorreram até a lâmina de 3 e 2 mm para o solo argiloso e siltoso, respectivamente. Nas quantidades iniciais de chuva (lâminas iniciais) a intensidade foi determinante na redução do DMP, com o aumento da quantidade de chuva a energia cinética (EC) passou a influenciar a redução do DMP. A intensidade de 28 mm h-1 promoveu as maiores reduções do DMP possivelmente pelo maior tempo de exposição dos agregados ao molhamento. / The crusts are the result of degradation of the surface structure of the soil, favoring erosion and environmental degradation of soils. This study evaluated the dynamics of the develop surface crusts and its consequences on the porosity, hydraulic conductivity (K), water retention, bulk density (Ds) and the roughness of a Typic Hapludult conducted with different systems of tillage and application of sheets simulated rainfall. Was also evaluated through the an laboratory experiment, the processes involved in the breakdown of aggregates under simulated rainfall. The experiment was conducted in the years 2009 and 2010. In plots of 15 x 30 m were installed the soil tillage: conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Inside of the plots was installed micro-plots of 1m x 1m, which were applied different sheets of simulated rainfall (0, 27, 54 and 80 mm) with intensity of 80 mm h-1. Roughness data, K measurements, sampling of undisturbed soil samples for porosity analysis and preparation of thin sections, and also cylindrical rings for water retention curve (SWRC) and Ds, were collected. In the laboratory experiment two soils (Silt Loam and Clay Loam) and two aggregate classes (1-3 and 3-5 mm) were used. The aggregates were submitted to different simulated rainfall (28mmh-1 + KE strong; 28mmh-1 + KE weak; 90mmh-1 + KE strong; 90mmh-1 + KE weak) and after the mean weight diameter (MWD) was evaluated. The dynamics of crust formation occurred differently in both tillage systems. In the CT and RT systems the major reduction of the porosity, by effect of the applied rainfall, occurred in the crust layer and in the NT system occurred in the subcrosta layer. Crust formation was responsible for reducing the porosity and K, and increasing Ds, in RT and CT systems. The higher volumetric moisture contents observed in CRA occurred in the PR system and the lowest in CT. The CRA did not show changes between the applied rainfall. The surface roughness of the soil varied in relation to the tillage systems. RT and NT systems showed a higher roughness in the first year during the second year a higher roughness was observed in the NT system. The CT in the two years studied showed the same trend of evolution according to of applied rainfall, initially there was an increase in roughness up to a maximum rain and then decrease. In the laboratory experiment, the largest DMP reductions occurred in the 3 and 2 mm rainfall for the Silt Loam and Clay Loam soils, respectively. In the initial amounts of rainfall, the intensity was determinant in the MWD reduction. With the increase in the amount of rainfall, the kinetic energy influences the MWD reduction. The intensity of 28 mm h-1 produced the greatest reductions in DMP, possibly due to the longer exposure of the aggregates to wetting.

As crostas são o resultado da degradação da estrutura superficial dos solos, favorecem a erosão e a degradação ambiental dos solos. Este estudo avaloiu a dinâmica da formação de crostas superficiais e as consequencias sobre a porosidade, condutividade hidráulica (K), retenção de água, densidade (Ds) e a rugosidade de um Argissolo Vermelho amarelo conduzido com diferentes sistemas de preparo do solo e aplicação de lâminas de chuva simulada. Avaliou-se também, através de um experimento em laboratório, os processos envolvidos na quebra dos agregados, sob chuvas simuladas. O experimento foi conduzido, nos anos de 2009 e 2010. Em parcelas de 15 x 30 m foram conduzidos os diferentes preparos do solo: preparo convencional (PC), preparo reduzido (PR) e sem preparo (SP). Dentro das parcelas instalou-se micro-parcelas de 1m x 1m, onde foram aplicadas diferentes lâminas de chuva simulada (0, 27, 54 e 80 mm) com intensidade de 80 mm h-1. Foram realizadas coletas de dados de rugosidade, medidas de K, coleta de amostras indeformadas de solo para análise da porosidade e confecção de lâminas delgadas, e também anéis cilíndricos para curva de retenção de água (CRA) e Ds do solo. No experimento de laboratório, utilizou-se dois solos (siltoso e argiloso) e duas classe de agregados (1-3 e 3-5 mm). Os agregados foram submetidos a diferentes chuvas simuladas (28mmh-1 + EC forte; 28mmh-1 + EC fraca; 90mmh-1 + EC forte; 90mmh-1 + EC fraca) e após avaliou-se o diâmetro médio ponderado dos agregados (DMP). A dinâmica da formação de crostas ocorreu de maneira diferenciada em ambos os sistemas de preparo. Nos sistemas de PC e PR a maior redução da porosidade, pelo efeito da chuva aplicada, ocorreu na camada da crosta e no sistema SP na camada da subcrosta. A camada da crosta foi responsável pela redução da porosidade e K, e aumento da Ds nos sistemas PC e PR. As maiores umidades volumétricas observadas nas CRA ocorreram no sistema de PR e as menores no PC e não demonstraram evolução entre as chuvas aplicadas. A rugosidade superficial do solo variou em função dos sistemas de preparo realizados. Os sistemas conservacionistas (PR e SP) apresentaram maior rugosidade no primeiro ano, no segundo ano a maior rugosidade foi observada no sistema SP. O PC demonstrou nos dois anos estudados a mesma tendência, em função das chuvas aplicadas, inicialmente ocorreu um aumento na rugosidade até uma chuva máxima diminuindo em seguida. No experimento em laboratório, as maiores reduções no DMP ocorreram até a lâmina de 3 e 2 mm para o solo argiloso e siltoso, respectivamente. Nas quantidades iniciais de chuva (lâminas iniciais) a intensidade foi determinante na redução do DMP, com o aumento da quantidade de chuva a energia cinética (EC) passou a influenciar a redução do DMP. A intensidade de 28 mm h-1 promoveu as maiores reduções do DMP possivelmente pelo maior tempo de exposição dos agregados ao molhamento. / The crusts are the result of degradation of the surface structure of the soil, favoring erosion and environmental degradation of soils. This study evaluated the dynamics of the develop surface crusts and its consequences on the porosity, hydraulic conductivity (K), water retention, bulk density (Ds) and the roughness of a Typic Hapludult conducted with different systems of tillage and application of sheets simulated rainfall. Was also evaluated through the an laboratory experiment, the processes involved in the breakdown of aggregates under simulated rainfall. The experiment was conducted in the years 2009 and 2010. In plots of 15 x 30 m were installed the soil tillage: conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Inside of the plots was installed micro-plots of 1m x 1m, which were applied different sheets of simulated rainfall (0, 27, 54 and 80 mm) with intensity of 80 mm h-1. Roughness data, K measurements, sampling of undisturbed soil samples for porosity analysis and preparation of thin sections, and also cylindrical rings for water retention curve (SWRC) and Ds, were collected. In the laboratory experiment two soils (Silt Loam and Clay Loam) and two aggregate classes (1-3 and 3-5 mm) were used. The aggregates were submitted to different simulated rainfall (28mmh-1 + KE strong; 28mmh-1 + KE weak; 90mmh-1 + KE strong; 90mmh-1 + KE weak) and after the mean weight diameter (MWD) was evaluated. The dynamics of crust formation occurred differently in both tillage systems. In the CT and RT systems the major reduction of the porosity, by effect of the applied rainfall, occurred in the crust layer and in the NT system occurred in the subcrosta layer. Crust formation was responsible for reducing the porosity and K, and increasing Ds, in RT and CT systems. The higher volumetric moisture contents observed in CRA occurred in the PR system and the lowest in CT. The CRA did not show changes between the applied rainfall. The surface roughness of the soil varied in relation to the tillage systems. RT and NT systems showed a higher roughness in the first year during the second year a higher roughness was observed in the NT system. The CT in the two years studied showed the same trend of evolution according to of applied rainfall, initially there was an increase in roughness up to a maximum rain and then decrease. In the laboratory experiment, the largest DMP reductions occurred in the 3 and 2 mm rainfall for the Silt Loam and Clay Loam soils, respectively. In the initial amounts of rainfall, the intensity was determinant in the MWD reduction. With the increase in the amount of rainfall, the kinetic energy influences the MWD reduction. The intensity of 28 mm h-1 produced the greatest reductions in DMP, possibly due to the longer exposure of the aggregates to wetting.

No description available.

No description available.