Current climate change trends are affecting the magnitude and recurrence of extreme weather events. In particular, several semi-arid regions around the planet are confronting more intense and prolonged lack of precipitation, slowly transforming these regions into deserts. In this thesis we present a stochastic (meso-scale) model for vegetation-precipitation interactions for semi-arid landscapes. Extensive simulations with the model suggest that persistence in current trends of precipitation decline in semi-arid landscapes may expedite desertification processes by up to several decades.

Changes with land cover and land use are closely integrated with water and other ecological processes at the land surface. Nowhere is that more apparent than in the Edwards Aquifer region of southcentral Texas. The Edwards Aquifer contributing and recharge zones cover approximately 18,000 square kilometers in parts of 15 counties in Texas and includes San Antonio and Austin, the nation's eighth and nineteenth largest cities, respectively. Population growth within the counties that intersect the Edwards Aquifer contributing and recharge zones has taken place over the last two decades, with the logical translation being an expanded infrastructure. This implies that a greater amount of impervious surface coverage and other land cover changes have occurred. This work quantified the changes in land cover within the Edwards Aquifer contributing and recharge zones between the years 1986 and 2000. Increasing trends in impervious surface area and woodland growth were identified. Additionally, a new ArcView software tool was developed to process SSURGO soil data for use within the ArcView SWAT model. Hydrologic modeling for the Upper Sabinal River watershed, located within the Edwards Aquifer region, revealed that the high resolution SSURGO data produces different results when used in place of the existing STATSGO soils data. Finally, an index of urbanization was developed and evaluated to assist investigators in identifying potential areas of urbanization.

116f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-04-03T15:36:36Z No. of bitstreams: 1 Dissertação Tadeu Antônio de Campos Costa.pdf: 7198947 bytes, checksum: 7254dbbef38a263048595926793a3ec7 (MD5) / Rejected by Ana Hilda Fonseca(anahilda@ufba.br), reason: trocar tese por dissertação on 2013-04-23T16:03:13Z (GMT) / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-04-23T16:05:02Z No. of bitstreams: 1 Dissertação Tadeu Antônio de Campos Costa.pdf: 7198947 bytes, checksum: 7254dbbef38a263048595926793a3ec7 (MD5) / Rejected by Ana Hilda Fonseca(anahilda@ufba.br), reason: Trocar tese por dissertação on 2013-04-23T16:08:55Z (GMT) / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-04-23T16:11:23Z No. of bitstreams: 1 Dissertação Tadeu Antônio de Campos Costa.pdf: 7198947 bytes, checksum: 7254dbbef38a263048595926793a3ec7 (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-05-09T15:50:00Z (GMT) No. of bitstreams: 1 Dissertação Tadeu Antônio de Campos Costa.pdf: 7198947 bytes, checksum: 7254dbbef38a263048595926793a3ec7 (MD5) / Made available in DSpace on 2013-05-09T15:50:00Z (GMT). No. of bitstreams: 1 Dissertação Tadeu Antônio de Campos Costa.pdf: 7198947 bytes, checksum: 7254dbbef38a263048595926793a3ec7 (MD5) Previous issue date: 2011 / CAPES / Para tornar potáveis águas salobras ou salinas, é necessário fazer a dessalinização, processo que normalmente exige alto investimento e recursos tecnológicos complexos para a produção em larga escala. Uma solução simples e eficiente para as comunidades do Semi Árido pode ser a dessalinização de água salobra pelo contato com materiais biológicos, através do uso de dispositivos caseiros contendo, por exemplo, sementes que adsorvam parte do sal da água, reduzindo a salinidade da mesma. Em estudo desenvolvido recentemente sobre a capacidade de sorção de sais de água salobra por sementes típicas de regiões semi áridas foram consideradas mais eficientes sementes de umbu (Spondias tuberosa Arruda) e Umburana (Amburana cearensis A. C. Smith). Em função disso, foi estudado neste trabalho o perfil químico desses materiais biológicos no seu estado natural e transformado em carvão quando aquecido a 250 °C por 1 hora, que foi a melhor condição encontrada para maior eficiência de dessalinização. Da análise fitoquímica da semente da umburana foi observada a presença de alcalóides, taninos, saponinas, cumarinas, triterpenos, esteróides e flavonóides, e o seu carvão apresentou resultados positivos para alcalóides, taninos, saponinas, esteróides e flavonóides. Na semente do umbu observou-se a presença de taninos, cumarinas, ácidos orgânicos, esteróides e flavonóides e no carvão não foram observados resultados positivos. No perfil dos ácidos graxos obtido por cromatografia gasosa (CG) dos ésteres metílicos produzidos por reação de esterificação dos extratos hexânicos das sementes, foram encontrados: na semente in natura da umburana dez ácidos graxos, sendo oito saturados (palmitíco, margárico, oléico, esteárico, nnonadecílico, araquídico, n-heneicosóico e lignocérico), um insaturado (ácido oléico) e outro que não foi possível identificar; o carvão desta semente apresentou os mesmos ácidos graxos, além do ácido mirístico; a semente in natura do umbu apresentou sete ácidos graxos saturados (mirístico, palmitíco, esteárico, nnonadecílico, araquídico, n-heneicosóico e behênico) e dois ácidos insaturados (oléico e linoléico); o seu carvão, apresentou a mesma composição dos ácidos graxos saturados que a semente in natura, mas apenas um insaturado (ácido oléico). A análise por CLAE dos extratos da semente da umburana in natura e como carvão e do umbu in natura revelou pela primeira vez à presença de ácido Lascórbico e ácido gálico nestes materiais biológicos. A presença de alcalóides identificados no carvão da umburana não é um bom indicativo para sua utilização como dessalinizador, devido à conhecida toxicidade de substâncias dessa família, assim como pela presença de cumarina, em função da sua toxicidade e solubilidade parcial em água. No entanto, devido à facilidade de obtenção da cumarina a partir da semente moída da umburana, sua utilização poderá ser viável em indústrias de produtos de limpeza e cosméticos ou como material de partida para síntese de fármacos, entre outros. No carvão produzido com a semente de umbu não foi identificado nenhum dos metabólitos encontrados na semente in natura e este resultado é promissor para a sua utilização como dessalinizador. No seu carvão foi observado apenas ácido L-ascórbico, substância solúvel em água, que além de evitar doenças, é extremamente importante no combate dos radicais livres oriundos de processos oxidativos. Além disso, este material, rico em ácidos graxos, poderá ser mais bem aproveitado, principalmente pela presença do ácido linoléico, considerado benéfico à saúde. / Salvador

NUNES, Francyregis Araújo. Efeitos da sazonalidade pluviométrica sobre a diversidade e a composição de uma assembléia de formigas (Hymenoptera: Formicidae) em uma área de caatinga. 2010. 85 f. Dissertação (Mestrado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2010. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-20T17:39:54Z No. of bitstreams: 1 2010_dis_fanunes.pdf: 2040918 bytes, checksum: b402d9f71700459f1d14b752eee42819 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-27T20:14:32Z (GMT) No. of bitstreams: 1 2010_dis_fanunes.pdf: 2040918 bytes, checksum: b402d9f71700459f1d14b752eee42819 (MD5) / Made available in DSpace on 2016-05-27T20:14:32Z (GMT). No. of bitstreams: 1 2010_dis_fanunes.pdf: 2040918 bytes, checksum: b402d9f71700459f1d14b752eee42819 (MD5) Previous issue date: 2010 / Presence of water is a determinant factor for food sources and/or nest sites availability, and is therefore potentially important for terrestrial invertebrate communities, particularly for those with fixed/perennial nests and that live in environments marked by strong rainfall seasonality. The aim of this work was to obtain informations about the seasonal patterns of a soil ant assembly structure of a Caatinga area, and to investigate how diversity and species composition of that assembly vary with rainfall seasonality. The study was performed in a Caatinga area localized at Pentecoste-CE. A 200 meters transect with 20 sampling points at 10 meters intervals was established. Transect sampling was performed once a month during 12 months, in the period 08/2008 – 08/2009. At each sampling point, a pitfall trap (height: 13 cm; diameter: 12 cm) filled with a ethanol/ethylenoglicol solution was placed at the beginning of each month and remained in the field for seven days. The taxonomic structure of the sampled fauna as well as the species (relative) frequency distribution followed the patterns generally found in neotropical regions. Forty-one species (40 in the dry season; 30 in the rainy season) belonging to six subfamilies and 20 genera were collected, with Myrmicinae (21 spp.), Pheidole (10 ssp) and Camponotus (8 spp) as the most specious taxa. Most species showed low (relative) abundance, being found in less than 10% of all the sampling units used in the whole sampling period. Only five species were collected in more than 50% of the sampling units. The collect of the relatively rare species Thaumatomyrmex mutilatus represents the second record of that species for the semi-arid northeastern region, whereas the collect of a new species, actually being described, of the Platythyrea genus represents the first record for the Ceará state. Of the 41 collected species, 12 and 1 (Strumigenys elongata) were found only during the dry and the rainy season respectively. The species-accumulation curves (observed and estimated) indicated that the sampling sufficiency was attained, and that about 90% of the estimated fauna had been collected. The Shannon and the Simpson diversity indexes for the rainy season were both lower compared to the dry season (H’: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), and there was a negative correlation between the monthly Shannon and Simpson diversity indexes and the pluviometric indexes. A reverse relationship was observed with the equability indexes (Pielou equability index and Simpson equability index) (Pielou equability: 0,79 versus 0,83; Simpson equability: 0,35 versus 0,44), with a significant positive correlation between the monthly Simpson equability indexes and the pluviometric indexes. The turnover indexes were low, with a mean of 0,23 between the consecutive months of the sampling period, and a value of 0,19 when comparing the two periods (dry and rainy). The average fauna similarity (Jaccard´s index) for the monthly samplings (0,61) and the fauna similarity for two periods (dry and rainy) (0,67) were high. The group analysis with the hierarchical clustering method (UPGMA) did not allow the detection of two clear-cut groups corresponding to the two periods (dry and rainy). Compared to other Brazilian biomes, the ant species richness found in the study was low, and the results suggest that the dry season is not a limiting factor for the ant communities of the Caatinga biome. Nevertheless, the diversity reduction observed in the rainy season could result from an important reduction of ant activity in response to an atypical/exceptional rainy period in the 2009 year. The reduced biodiversity, when compared to other Brazilian biomes, could result from the permanent or seasonal lack of leaf-litter, an important factor for the specialized soil ant predators, and from the possible carbohydrates seasonal limitation (nectar, honeydew). / A presença de água é um fator determinante na disponibilidade de fontes de alimento e/ou de sítios de nidificação, e é, portanto, potencialmente importante para as comunidades de invertebrados terrestres, particularmente para animais com ninhos fixos/perenes e vivendo em ambientes marcados por uma forte sazonalidade pluviométrica. O objetivo deste trabalho foi obter informações sobre os padrões sazonais de estrutura de uma assembléia de formigas de solo da Caatinga e investigar como a diversidade e a composição dessa assembléia variam com a sazonalidade pluviométrica. O estudo foi realizado em uma área de Caatinga arbórea localizada em Pentecoste - CE. Um transecto de 200 metros com 20 unidades amostrais espaçadas entre si por 10 metros foi estabelecido. A amostragem no transecto foi realizada uma vez por mês durante 12 meses, no período 08/2008 – 08/2009. Em cada unidade amostral, uma armadilha de solo (13 cm de altura; 12 cm de diâmetro) com solução de etanol/etilenoglicol foi instalada no início de cada mês e ficou operacional durante uma semana. A estrutura taxonômica da fauna amostrada e a distribuição de freqüência (relativa) das espécies seguem os padrões geralmente encontrados nas regiões neotropicais. Foram coletadas 41 espécies (40 na estação seca, 30 na estação chuvosa), pertencentes a seis subfamílias e 20 gêneros, sendo a subfamília Myrmicinae (21 spp.) e os gênero Pheidole (10 spp.) e Camponotus (8 spp.) com maior riqueza em espeçies. A maioria das espécies foi pouco abundante, sendo capturada em menos de 10% das unidades amostrais de todo o período de coleta. Apenas cinco espécies foram coletadas em mais de 50% das unidades amostrais. A coleta da espécie relativamente rara Thaumatomyrmex mutilatus representa o segundo registro dessa espécie para o Nordeste semi-árido, enquanto a coleta de uma nova espécie, em fase de descrição, do gênero Platythyrea representa o primeiro registro para o Ceará. Das 41 espécies, 12 foram exclusivas da estação seca e uma (Strumigenys elongata) da estação chuvosa. As curvas de acumulação de espécies (observadas e estimadas) demonstraram que a suficiência amostral foi atingida, bem como indicam que em torno de 90% da riqueza estimada foi coletada. Tanto o índice de diversidade de Shannon como o de Simpson, foi menor na estação chuvosa em relação à estação seca (H’: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), e houve correlação negativa entre os índices de diversidade mensais de Shannon e Simpson, e os índices pluviométricos. A relação inversa foi constatada para os índices de equabilidade (equabilidade de Pielou: 0,79 versus 0,83; equabilidade de Simpson: 0,35 versus 0,44), com existência de uma correlação positiva significativa entre os índices de equabilidade mensais de Simpson e os índices pluviométricos. Os índices de ―turnover‖ foram baixos, com média de 0,23 entre os meses consecutivos do período de coleta, e com valor de 0,19 na comparação dos dois períodos (seco e chuvoso). A similaridade de fauna (índice de Jaccard) entre as coletas mensais (média de 0,61) e entre os dois períodos (0,67) foi relativamente elevada. A análise de agrupamento (UPGMA) não permitiu detectar a existências de dois grupos claramente definidos em relação aos dois períodos (seco e chuvoso). A riqueza em espécies foi considerada baixa, comparativamente a outros biomas brasileiros, e os resultados sugerem que o período seco na Caatinga não é um fator limitante para as comunidades de formigas. Entretanto, a redução de diversidade observada na estação chuvosa poderia ser o reflexo de uma importante redução das atividades das formigas decorrente de um quadro chuvoso atípico/excepcional do ano 2009. A biodiversidade reduzida em relação a outros biomas brasileiros poderia resultar da falta permanente ou sazonal de serrapilheira, importante para as espécies predadoras de solo especialistas, e da possível limitação sazonal de carboidratos (néctar e ―honeydew‖).

FIALHO, Jamili Silva. Qualidade do solo e pedofauna em sistemas tradicionais e agroflorestais. 2013. 83 f. Tese (Doutorado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2013. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-27T19:36:39Z No. of bitstreams: 1 2013_tese_jsfialho.pdf: 1474504 bytes, checksum: 6813b13031c48a26ebdbb140a76a6f4e (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-27T20:48:08Z (GMT) No. of bitstreams: 1 2013_tese_jsfialho.pdf: 1474504 bytes, checksum: 6813b13031c48a26ebdbb140a76a6f4e (MD5) / Made available in DSpace on 2016-05-27T20:48:08Z (GMT). No. of bitstreams: 1 2013_tese_jsfialho.pdf: 1474504 bytes, checksum: 6813b13031c48a26ebdbb140a76a6f4e (MD5) Previous issue date: 2013 / Traditional agriculture can degrade natural resources becoming unsustainable. Hence, ecological approaches on agriculture enable the choice of agricultural management,which associates food production and the maintenance of natural resources, as agroforestry systems. The simplified agroecosystem reduces diversity, causing deleterious effects on soil biota and on soil quality,. Thus, the aim of this work was: i) to assess quality indicators and soil quality, resistance and resilience indexes, ii) to evaluate the diversity of edaphic fauna of agroecosystems and iii) to identify flora and dry and rainy seasons to edaphic fauna abundance. Agrosilvopastoral, silvopastoral, and traditional agroecosystems were studied, under use and under different periods of fallow, besides the natural vegetation (MATA). Soil quality (QS) was analyzed according to some indicators and from them quality, resistance and resilience indexes were calculated. Edaphic fauna was collected under dry and rainy seasons, using PITFALL TRAPS. The fauna was identified under taxonomic groups and the indexes: abundance, density, diversity, and uniformity here determined. The relation between fauna and flora and the seasons was analyzed using general linear models. Agroforestries maintained QS, traditional system under fallow recovered it, and the traditional system reduced it and it was less resilient and resistant. In the dry season, agroforestries showed low diversity and uniformity, therefore presenting similar abundance to MATA, while areas under fallow showed high diversity and uniformity. There were similarities in diversity and uniformity between traditional system and MATA. In the rainy season, agroforestries showed density and abundance similar to MATA,. Traditional systems under fallow showed density, abundance, diversity, and uniformity similar to MATA. It is possible to conclude that agroforestry systems are sustainable. Six and nine years of fallow are enough to recover the condition of natural vegetation. Traditional management reduces quality, resistance and resilience of soil. Agroforestries show diversity and uniformity of pedofauna similar to the natural vegetation when water is available. The abundance of trees and weather seasonality determine the abundance of pedofauna. / A prática da agricultura tradicional pode degradar a qualidade dos recursos naturais e por isso se tornar insustentável, o que leva a necessidade de uma abordagem ecológica, possibilita a escolha de manejos agrícolas que associem a produção de alimentos e a conservação dos recursos naturais, como acontece nos sistemas agroflorestais. A simplificação do agroecossistema reduz a diversidade, afetando a biota e a qualidade do solo. Assim, objetivou-se: i) avaliar indicadores da qualidade e índices da qualidade, resistência e resiliência do solo, ii) avaliar a diversidade da pedofauna dos agroecossistemas e iii) identificar as relações entre a flora nos períodos seco e chuvoso com a riqueza da pedofauna. Foram estudados os sistemas agroflorestais do tipo agrossilvipastoril, silvipastoril e o tradicional, atualmente em uso e após diferentes períodos de pousio; além de um sistema menos impactado (MATA). A qualidade do solo (QS) foi avaliada por indicadores químicos e físicos de solo e calculados os índices de qualidade, resistência e resiliência. A pedofauna foi coletada, nos períodos seco e chuvoso, usando armadilhas de queda, identificando-se os grupos taxonômicos e posterior determinação da riqueza, densidade, diversidade e uniformidade. As áreas sob sistemas agroflorestais mantiveram a QS, o pousio recuperou e o tradicional a reduziu, sendo menos resiliente e resistente. No período seco, os sistemas agroflorestais apresentaram baixas diversidade e uniformidade, porém riquezas semelhante à MATA, enquanto que as áreas em pousio apresentaram altas diversidade e uniformidade. Houve semelhanças de diversidade e uniformidade entre as áreas sob cultivo tradicional e MATA. No período chuvoso, os sistemas agroflorestais apresentaram densidade e riqueza semelhantes à MATA. As áreas tradicionais em pousio apresentaram densidade, riqueza, diversidade e uniformidade semelhantes à MATA. Conclui-se que os sistemas agroflorestais são sustentáveis, seis e nove anos de pousio são suficientes para retomar a condição do sistema menos impactado e manejo tradicional reduz a qualidade, resistência e resiliência do solo. Os sistemas agroflorestais apresentam diversidade e uniformidade da pedofauna semelhantes ao ambiente menos impactado quando há disponibilidade hídrica. A riqueza das espécies arbóreas e a sazonalidade climática determinam a riqueza da pedofauna.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A presenÃa de Ãgua à um fator determinante na disponibilidade de fontes de alimento e/ou de sÃtios de nidificaÃÃo, e Ã, portanto, potencialmente importante para as comunidades de invertebrados terrestres, particularmente para animais com ninhos fixos/perenes e vivendo em ambientes marcados por uma forte sazonalidade pluviomÃtrica. O objetivo deste trabalho foi obter informaÃÃes sobre os padrÃes sazonais de estrutura de uma assemblÃia de formigas de solo da Caatinga e investigar como a diversidade e a composiÃÃo dessa assemblÃia variam com a sazonalidade pluviomÃtrica. O estudo foi realizado em uma Ãrea de Caatinga arbÃrea localizada em Pentecoste - CE. Um transecto de 200 metros com 20 unidades amostrais espaÃadas entre si por 10 metros foi estabelecido. A amostragem no transecto foi realizada uma vez por mÃs durante 12 meses, no perÃodo 08/2008 â 08/2009. Em cada unidade amostral, uma armadilha de solo (13 cm de altura; 12 cm de diÃmetro) com soluÃÃo de etanol/etilenoglicol foi instalada no inÃcio de cada mÃs e ficou operacional durante uma semana. A estrutura taxonÃmica da fauna amostrada e a distribuiÃÃo de freqÃÃncia (relativa) das espÃcies seguem os padrÃes geralmente encontrados nas regiÃes neotropicais. Foram coletadas 41 espÃcies (40 na estaÃÃo seca, 30 na estaÃÃo chuvosa), pertencentes a seis subfamÃlias e 20 gÃneros, sendo a subfamÃlia Myrmicinae (21 spp.) e os gÃnero Pheidole (10 spp.) e Camponotus (8 spp.) com maior riqueza em espeÃies. A maioria das espÃcies foi pouco abundante, sendo capturada em menos de 10% das unidades amostrais de todo o perÃodo de coleta. Apenas cinco espÃcies foram coletadas em mais de 50% das unidades amostrais. A coleta da espÃcie relativamente rara Thaumatomyrmex mutilatus representa o segundo registro dessa espÃcie para o Nordeste semi-Ãrido, enquanto a coleta de uma nova espÃcie, em fase de descriÃÃo, do gÃnero Platythyrea representa o primeiro registro para o CearÃ. Das 41 espÃcies, 12 foram exclusivas da estaÃÃo seca e uma (Strumigenys elongata) da estaÃÃo chuvosa. As curvas de acumulaÃÃo de espÃcies (observadas e estimadas) demonstraram que a suficiÃncia amostral foi atingida, bem como indicam que em torno de 90% da riqueza estimada foi coletada. Tanto o Ãndice de diversidade de Shannon como o de Simpson, foi menor na estaÃÃo chuvosa em relaÃÃo à estaÃÃo seca (Hâ: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), e houve correlaÃÃo negativa entre os Ãndices de diversidade mensais de Shannon e Simpson, e os Ãndices pluviomÃtricos. A relaÃÃo inversa foi constatada para os Ãndices de equabilidade (equabilidade de Pielou: 0,79 versus 0,83; equabilidade de Simpson: 0,35 versus 0,44), com existÃncia de uma correlaÃÃo positiva significativa entre os Ãndices de equabilidade mensais de Simpson e os Ãndices pluviomÃtricos. Os Ãndices de ―turnover‖ foram baixos, com mÃdia de 0,23 entre os meses consecutivos do perÃodo de coleta, e com valor de 0,19 na comparaÃÃo dos dois perÃodos (seco e chuvoso). A similaridade de fauna (Ãndice de Jaccard) entre as coletas mensais (mÃdia de 0,61) e entre os dois perÃodos (0,67) foi relativamente elevada. A anÃlise de agrupamento (UPGMA) nÃo permitiu detectar a existÃncias de dois grupos claramente definidos em relaÃÃo aos dois perÃodos (seco e chuvoso). A riqueza em espÃcies foi considerada baixa, comparativamente a outros biomas brasileiros, e os resultados sugerem que o perÃodo seco na Caatinga nÃo à um fator limitante para as comunidades de formigas. Entretanto, a reduÃÃo de diversidade observada na estaÃÃo chuvosa poderia ser o reflexo de uma importante reduÃÃo das atividades das formigas decorrente de um quadro chuvoso atÃpico/excepcional do ano 2009. A biodiversidade reduzida em relaÃÃo a outros biomas brasileiros poderia resultar da falta permanente ou sazonal de serrapilheira, importante para as espÃcies predadoras de solo especialistas, e da possÃvel limitaÃÃo sazonal de carboidratos (nÃctar e ―honeydew‖) / Presence of water is a determinant factor for food sources and/or nest sites availability, and is therefore potentially important for terrestrial invertebrate communities, particularly for those with fixed/perennial nests and that live in environments marked by strong rainfall seasonality. The aim of this work was to obtain informations about the seasonal patterns of a soil ant assembly structure of a Caatinga area, and to investigate how diversity and species composition of that assembly vary with rainfall seasonality. The study was performed in a Caatinga area localized at Pentecoste-CE. A 200 meters transect with 20 sampling points at 10 meters intervals was established. Transect sampling was performed once a month during 12 months, in the period 08/2008 â 08/2009. At each sampling point, a pitfall trap (height: 13 cm; diameter: 12 cm) filled with a ethanol/ethylenoglicol solution was placed at the beginning of each month and remained in the field for seven days. The taxonomic structure of the sampled fauna as well as the species (relative) frequency distribution followed the patterns generally found in neotropical regions. Forty-one species (40 in the dry season; 30 in the rainy season) belonging to six subfamilies and 20 genera were collected, with Myrmicinae (21 spp.), Pheidole (10 ssp) and Camponotus (8 spp) as the most specious taxa. Most species showed low (relative) abundance, being found in less than 10% of all the sampling units used in the whole sampling period. Only five species were collected in more than 50% of the sampling units. The collect of the relatively rare species Thaumatomyrmex mutilatus represents the second record of that species for the semi-arid northeastern region, whereas the collect of a new species, actually being described, of the Platythyrea genus represents the first record for the Cearà state. Of the 41 collected species, 12 and 1 (Strumigenys elongata) were found only during the dry and the rainy season respectively. The species-accumulation curves (observed and estimated) indicated that the sampling sufficiency was attained, and that about 90% of the estimated fauna had been collected. The Shannon and the Simpson diversity indexes for the rainy season were both lower compared to the dry season (Hâ: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), and there was a negative correlation between the monthly Shannon and Simpson diversity indexes and the pluviometric indexes. A reverse relationship was observed with the equability indexes (Pielou equability index and Simpson equability index) (Pielou equability: 0,79 versus 0,83; Simpson equability: 0,35 versus 0,44), with a significant positive correlation between the monthly Simpson equability indexes and the pluviometric indexes. The turnover indexes were low, with a mean of 0,23 between the consecutive months of the sampling period, and a value of 0,19 when comparing the two periods (dry and rainy). The average fauna similarity (JaccardÂs index) for the monthly samplings (0,61) and the fauna similarity for two periods (dry and rainy) (0,67) were high. The group analysis with the hierarchical clustering method (UPGMA) did not allow the detection of two clear-cut groups corresponding to the two periods (dry and rainy). Compared to other Brazilian biomes, the ant species richness found in the study was low, and the results suggest that the dry season is not a limiting factor for the ant communities of the Caatinga biome. Nevertheless, the diversity reduction observed in the rainy season could result from an important reduction of ant activity in response to an atypical/exceptional rainy period in the 2009 year. The reduced biodiversity, when compared to other Brazilian biomes, could result from the permanent or seasonal lack of leaf-litter, an important factor for the specialized soil ant predators, and from the possible carbohydrates seasonal limitation (nectar, honeydew)

Anthropogenic disturbances are increasing in arid lands, as are expectations to successfully minimize impacts to natural resources and reclaim sites to publicly acceptable levels. This research explores the effectiveness of reclamation practices on a 60 mile natural gas pipeline constructed in September of 2014 that spans from west of Tucson to the border of Mexico. First, a controlled field experiment was conducted to assess the effects of seeding, grazing, and trampling (vehicular, cattle, and human foot traffic) on the reclaimed pipeline Right-Of-Way (ROW). Vegetation establishment (native plant cover; undesirable plant cover; species richness; herbaceous biomass), soil movement, and plant functional group community development was compared among the treatments. Reclaimed ROW areas left to recover without seeding resulted in similar vegetation cover, species, and community composition as undisturbed desert areas, although the presence of undesirable species was greater. The combined impacts of grazing and trampling resulted in reduced vegetation establishment and increased soil erosion. Second, the impacts of the pipeline construction on ephemeral wash channels were analyzed in terms of channel morphology and riparian vegetation changes. Channel cross section dimensions were measured upstream of the ROW, downstream of the ROW, and within the ROW before and after the 2015 Monsoon season to evaluate impacts on channel morphology and erosion processes. High resolution aerial imagery taken before and after pipeline construction was used to evaluate changes in riparian vegetation cover. Reduced herbaceous vegetation cover downstream of the ROW was detected, which may have been the result of increased channel scour within the ROW and increased sediment deposition downstream of the ROW. This research improves our understanding of and may aid in selection of appropriate reclamation practices.

Agriculture for rural communities in semi-arid areas is a risky exercise. The adverse weather conditions (high evaporative demand and low rainfall) of these regions, coupled with comparatively limited mechanization and often soil of poor chemical and physical constitution make crop production difficult and seldom sustainable. To some this problem represents a conundrum to be solved, to others an inconvenience to be avoided. Reduction of agricultural risk in these communities can be addressed in numerous ways, but should always begin with a thorough investigation of the agricultural imperatives of the community targeted, with the recommended system then tailored specifically to meet these imperatives. Agroforestry (combining trees and crops in agricultural systems temporally or spatially simultaneously) has been recommended for, and often been very successful in, many rural communities in tropical Africa and Asia. Adoption in semi-arid Africa has been less widespread, and often less successful once implemented. Nevertheless, the risk reduction possibilities that agroforestry offers through crop complementarity and yield diversification warrant further investigation into the practice in these regions. These studies sought to quantify yield advantage or disadvantage of hedgerow intercropping or alleycropping systems (combining hedgerow Leucaena leucocephala with various annual alley crops of importance to rural South African communities) compared to pure stands, and to investigate the use and distribution of, and competition for, water and light in these systems. Although alley-cropped annuals seldom outperformed pure stand annual crops, the diversification of yield, enabled by combining trees and crops, compensated for lower yields of annual crops in dry seasons or when yield losses occurred through disease. Whether or not this compensation for yield loss would be to the ultimate benefit of the target community would depend on the relative value of the different products resulting from the intercropping system. Using modifications of the renowned Land Equivalent Ratio and energy contents of products of the system, attempts were made to quantify possible benefits of intercropping in terms valid for the community targeted. Studies of water and light distribution in these systems illuminated often-severe water shortages in alley rows close to hedgerows and showed little benefit in altering row orientation for improved light distribution. Water emerged, as expected, as the primary concern to possible adopters of these systems in semi-arid zones. Crop modeling with mechanistic, biophysically sound models should be considered as an extremely important tool in combining needs of communities with environmental constraints of the area targeted. / Dissertation (MSc(Agric) : Pasture Science)--University of Pretoria, 2008. / Plant Production and Soil Science / unrestricted

Pearl millet is a staple food source for millions of African families living in semi-arid regions of the continent. Yet, despite its importance and ability to provide consistent yields, very little research and resources have been directed towards understanding mechanisms governing this crop’s resilience to biotic and abiotic stresses. The research outlined in this thesis therefore aimed to elucidate defence response mechanisms in pearl millet, a non-model cereal crop. This was accomplished through the construction and characterisation of a pearl millet defence response cDNA library, which was subsequently utilised in large scale gene expression studies to profile pearl millet’s response to the defence signalling compounds nitric oxide (NO), methyl jasmonate (MeJA) and salicylic acid (SA), and to the biotrophic rust fungus Puccinia substriata var. indica. A pearl millet cDNA library was constructed by treating pearl millet plants with the defence elicitors chitin and flagellin, and by wounding the plants. Suppression subtractive hybridisation (SSH) was employed to enrich the library for defence response transcripts. In order to characterise the cDNA libraries, a quantitative cDNA microarray-based screening method was developed that enabled identification of false positive transcripts, as well as clones that represented rare or abundant transcripts. Based on this screening method, a number of clones were selected for sequence analysis, and their identity ascertained through homology searches with previously sequenced genes. This revealed a number of genes known to play important roles during pathogen attack. The pearl millet SSH defence response library, consisting of 1920 cDNAs either up- or down regulated in defence response, was spotted onto a glass slide microarray and used in transcript profiling studies to examine pearl millet’s response to the defence signalling molecules NO, MeJA and SA. Whilst only 45 cDNAs responded significantly to NO treatment, 279 and 224 cDNAs responded to MeJA and SA sprays, respectively. Closer examination of MeJA and SA responsive genes revealed that many of the induced transcripts were common to both signalling pathways, demonstrating that a substantial network of regulatory interactions exists between the salicylate and jasmonate pathways, which were previously believed to act in an antagonistic manner. Pathology studies indicated that pretreatment of pearl millet with SA conferred resistance to a virulent isolate of P. substriata var. indica, whereas MeJA application did not significantly reduce subsequent infection levels. Transcript profiling of a susceptible pearl millet line in response to virulent rust infection revealed that genes common to both the jasmonate and salicylate pathways were induced, suggesting that the plant adopts elements from a number of defence signalling pathways in an attempt to ward off infection by the virulent rust fungus. However, in view of results obtained from pearl millet defence signalling molecule pretreatments, it is probably genes that are significantly induced in response to SA, but to a lesser extent by MeJA that actually confer resistance to an avirulent rust isolate. Treatment of pearl millet plants with an avirulent P. substriata strain and subsequent microarray analysis would answer this hypothesis by revealing whether an incompatible reaction elicits more elements of the salicylate defence response pathway. / Thesis (PhD (Botany))--University of Pretoria, 2009. / Plant Science / unrestricted

Bats inhabiting arid, subtropical environments face diverse challenges related to energy and water balance. First, they may have to conserve water and energy during cool, dry winters when water is scarce and insect availability reduced. Second, during hot summers when air temperature may routinely exceed body temperature, bats may need to avoid both hyperthermia and dehydration. A common response to the energetically challenging winter period in temperate, subtropical and tropical species is heterothermy (i.e. torpor and hibernation). Despite evidence suggesting that heterothermy is of major significance in the energy balance of tropical and subtropical bats, its occurrence in southern African species especially those in semi-arid subtropical regions have received relatively little attention. Moreover, the physiological and thermoregulatory responses of bats to high air temperatures (Ta) are relatively poorly known. The goal of my project was to investigate various seasonal physiological challenges imposed on bats in an arid, sub-tropical climate. I investigated the occurrence of winter heterothermy in Nycteris thebaica (Nycteridae) in the Limpopo Valley. Skin temperatures (Tskin) were measured using temperature-sensitive transmitters, and roost temperatures (Troost) were recorded using miniature temperature loggers. N. thebaica used multiple roosting sites, including a hollow baobab tree (Adansonia digitata) and several caves, and exhibited only moderate heterothermy. Tskin was maintained around normothermic levels, with differences of 3-9°C (7.5±1.7°C) between overall maximum and minimum Tbs. A minimum Tskin of 28.4°C occurred at Troost = 23.8°C, and patterns of thermoregulation did not appear to be influenced by prevailing weather conditions. Roost temperatures did not decrease below 10°C, and averaged 21.2±2.8°C and 23.3±2.9°C respectively. The lack of pronounced heterothermy in N. thebaica is surprising, particularly in view of the daily torpor cycles observed in many insectivorous bat species. I also investigated the physiological responses of three sympatric bat species during summer using an open-flow respirometry system to measure resting metabolic rates (RMR) and evaporative water loss (EWL) over a range of Tas ~ 10-42°C, with body temperatures (Tb) simultaneously recorded via temperature-sensitive passive integrated transponder (PIT) tags. Basal metabolic rates for Nycteris thebaica and Taphozous mauritianus were 8.9±2.7mW.g-1 and 6.6±2.2mW.g-1 respectively, falling within the 95% prediction intervals for bat BMR, whereas the value for Sauromys petrophilus (3.4±0.6mW.g-1) fell below the lower 95% prediction interval. Maximum EWL for N. thebaica, T. mauritianus and S. petrophilus were 18.6±2.1mg.g-1.h-1 (Ta=39.4°C), 14.7±3.1mg.g-1.h-1 (Ta=41.9°C) and 23.7±7.4mg.g-1.h-1 (Ta=41.7°C) respectively. Maximum individual Tbs recorded were 46.5°C in N. thebaica (Ta=39.3°C), 44.9°C in T. mauritianus (Ta=41.8°C) and 46.5°C in S. petrophilus (Ta=41.7°C). Overall, I found that N. thebaica was the least heat tolerant species, with T. mauritianus and S. petrophilus being more heat tolerant. In the face of climate change, heat tolerance together with specific thermal properties of a given roost may play a major role in the ability of a species to persist in a hot, arid environment. / Dissertation (MSc)--University of Pretoria, 2012. / Zoology and Entomology / unrestricted