A drive into the country will soon confirm the effects of agriculture on the environment. Different agricultural practices such as vast fields of monocultures, forests of exotic timber, and large intensive feed lots of livestock, will be evident. The need to provide food for an increasing population particularly in Africa is the driving force behind the intensification of agriculture. The production of increased food supply is often considered without knowledge of the impacts on the environment. The North East District of Botswana is a small district compared to other districts of Botswana but unlike these large districts the population density is comparably high with a demand for agricultural space. Botswana is a desert margins area under threat of desertification with many signs of desertification being evident throughout the country. The main agricultural activity in the North East District is livestock farming with horticulture being practiced on the banks of sandy river beds. The district provided an ideal area to compare the impacts of different livestock farming techniques. Four different approaches of livestock farming were examined with the number of livestock cattle in particular, being a noticeable difference and the grazing intensity of these cattle being another important difference. This study examined the impacts of these different grazing techniques on the environment with a particular reference to birds. Data was collected using a point count system with 28 points evenly spaced in a grid across the different land uses. Each point was subject to a total of six surveys with summer and winter having three surveys each. It was expected that bird numbers and species would be impacted by the grazing intensity while the different feeding and nesting guilds may also respond to grazing intensity. Statistical analysis included geostatistical analysis, uni-variant, mult-variant and non-metric multi-dimensional scaling. The results show that birds were impacted by grazing intensity with species richness and bird numbers being negatively affected. However, feeding and nesting guilds were impacted differently. Climate change and land degradation are a reality and will impact on avian diversity and sound management practices need to be implemented to protect biodiversity in marginal areas. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

A drive into the country will soon confirm the effects of agriculture on the environment. Different agricultural practices such as vast fields of monocultures, forests of exotic timber, and large intensive feed lots of livestock, will be evident. The need to provide food for an increasing population particularly in Africa is the driving force behind the intensification of agriculture. The production of increased food supply is often considered without knowledge of the impacts on the environment. The North East District of Botswana is a small district compared to other districts of Botswana but unlike these large districts the population density is comparably high with a demand for agricultural space. Botswana is a desert margins area under threat of desertification with many signs of desertification being evident throughout the country. The main agricultural activity in the North East District is livestock farming with horticulture being practiced on the banks of sandy river beds. The district provided an ideal area to compare the impacts of different livestock farming techniques. Four different approaches of livestock farming were examined with the number of livestock cattle in particular, being a noticeable difference and the grazing intensity of these cattle being another important difference. This study examined the impacts of these different grazing techniques on the environment with a particular reference to birds. Data was collected using a point count system with 28 points evenly spaced in a grid across the different land uses. Each point was subject to a total of six surveys with summer and winter having three surveys each. It was expected that bird numbers and species would be impacted by the grazing intensity while the different feeding and nesting guilds may also respond to grazing intensity. Statistical analysis included geostatistical analysis, uni-variant, mult-variant and non-metric multi-dimensional scaling. The results show that birds were impacted by grazing intensity with species richness and bird numbers being negatively affected. However, feeding and nesting guilds were impacted differently. Climate change and land degradation are a reality and will impact on avian diversity and sound management practices need to be implemented to protect biodiversity in marginal areas. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Worldwide degradation and conversion of tropical forests affects many species and their provided ecosystem services. Among them are birds, responsible for pollination, seed dispersal, pest control and scavenging. This study, conducted in southwest Ethiopia, compares species composition and bird functional diversity between forest and homegardens close to and far from forest, both in terms of species numbers and bird abundances. Point counts and mist netting were used to obtain data. While the former method detected more species, abundance data from the latter revealed patterns not observed by just comparing species numbers. I found that species diversity was lower in forest compared to gardens and that the species composition of both communities was significantly distinct. Whereas forest had more forest specialists, gardens held more forest visitors and species of open country. Close and far gardens did not differ in any aspect, except that abundances of forest generalist birds were somewhat higher close to forest. Regarding bird feeding guilds, I found that granivores and nectarivores were more numerous in gardens, while frugivores were more common in forest. Carnivores and omnivores showed no effect. Insectivore proportions were the same for forest and farmland, but their numbers (including those of all sub-guilds) were higher in gardens. The Ethiopian forest avifauna is poor in comparison with other Afromontane regions, lacking several, mostly insectivorous genera. This could be the result of an extinction after which its geographic isolation made recolonization difficult, especially for dispersal-limited understory species. Nonetheless, and despite their impoverished state, the results suggest that forest remnants are important for forest-dependent species, being a stronghold for forest specialists and supporting higher numbers of forest generalists in nearby gardens. However, future forest regrowth might be at stake with ongoing agricultural encroachment, because gardens hold fewer frugivores, especially forest specialists, which might affect seed dispersal. / Många arter påverkas negativt av avskogning och annan mänsklig påverkan på tropiska skogar, vilket också kan få konsekvenser för de ekosystemtjänster dessa arter levererar. En viktig artgrupp i detta avseende är fåglar, som kan ha betydelse för pollination, fröspridning, naturlig skadedjurskontroll och som asätare. Denna studie, utförd i sydvästra Etiopien, jämför artsammansättning och funktionell diversitet hos fåglar i skogar och trädgårdar både nära och långt ifrån skogen. Både antal arter och antal individer har undersökts. Data materialet bygger både på observationer från punktinventering och fåglar fångade med slöjnät. Med den första metoden noterade jag fler arter, medan abundansvärden från den andra metoden gjorde att jag såg mönster som inte syntes vid endast jämförelser av artrikedom. Jag fann att artrikedomen var lägre i skogen i jämförelse med trädgårdarna, men att artsammansättningen var signifikant skiljd däremellan. Skogarna hade fler skogsspecialister medan trädgårdarna hade fler arter från öppna marker och tillfälliga skogsbesökande arter. Trädgårdar som låg nära eller långt ifrån skogen skiljde sig inte på något sätt utom att individtätheten av skogsgeneralister var något högre i trädgårdar nära skogen. När det gäller uppdelningen av fåglarna utifrån vad de äter så fann jag att fröätande och nektarätande arter var vanligare i trädgårdar medan fruktätande arter var vanligare i skogen. Rovfåglar och allätare uppvisade inget tydligt mönster. Proportionen insektsätande fåglelarter var samma i skogen och trädgårdarna, men det absoluta antalet arter (inklusive alla olika underkategorier) var högre i trädgårdarna. Den etiopiska skogsfågelfaunan är artfattig i förhållande till andra bergstrakter i Afrika och saknar flera släkten av framförallt insektsätande fåglar. Detta skulle kunna bero på ett tidigare utdöende varefter en senare återkolonisering varit svår på grund av den geografiska isoleringen, speciellt för insektsätande fåglar som huvudsakligen finns i undervegetationen. Trots den relativa artfattigdomen så visar resultatet från min studie hursomhelst på att skogarna är viktiga för skogsberoende fåglar. Den största betydelsen har de för skogsspecialister där, men även genom en positiv effekt på abundansen av skogsgeneralister i närliggande trädgårdar. Dock kan framtida återväxt av skogar bli problematisk på grund av en pågående omvandling av skogar till trädgårdar, eftersom trädgårdar hyser färre fruktätande fåglar, vilket kan påverka fröspridning över landskapet. / Examining mismatches between management and the supply of ecosystem services in Ethiopian agroecosystems across scales in space and time

This dissertation addresses large-scale trends in composition, density, taxonomic and functional diversity in deep-sea benthic polychaete communities in the Gulf of Mexico (GoM). The study includes samples from two major sampling programs: the Deep Gulf of Mexico Benthos (DGoMB) program (2000–2002) (51 stations, 200-3700 m) and the SIGSBEE program (Universidad Nacional Autónoma de México), 2008-2010 (27 stations on the Sigsbee Abyssal Plain). Polychaete density decreased exponentially with depth. Alpha diversity did not show a mid-depth maximum and reached its peak near the Mississippi trough. Feeding guild diversity was also highest in the Mississippi trough. The environmental parameters that determine diversity and density of polychaete assemblages and species distribution ranges were examined. Depth, export flux of particulate organic carbon (POC), percent sand and silt were the best predictors of heterogeneity of polychaetes in the GoM. We performed an ecological niche modeling analysis (ENM) based on ‘presence-only’ data of four cosmopolitan species belonging to the Cirratulidae and Spionidae in the GoM. The GoM, being a semi-enclosed ocean basin, offers complex topographic features and hydrographic processes. Comparisons of the overall polychaete diversity and richness patterns from this study for this region indicate a strong geographic variation with increasing depth and distance from the shore. Additionally, the environmental gradients observed play a major role in shaping the spatial distribution of polychaete communities in this region.

This study examines the impact of forest age on bird morphology and feeding guilds within the Kibale National Park, Uganda. Bird morphology is closely linked to their environment, effecting their ability to find food, avoid predators, and attract mates. Species characteristics in bird communities could change along the forest successional gradient, as different species or guilds exhibit preferences for specific stages of forest succession. Habitat preferences, such as the availability of nesting sites, foraging opportunities, and food availability, can be directly affected by changes in forest age. Life history traits like reproductive strategies and tolerance to disturbance and ecological interactions, such as competition, predation, and mutualism, can also be influenced by forest age. Changes in forest structure and resource availability can alter these dynamics, leading to shifts in species composition and community structure.  In this work data was derived from a study conducted in 2016, following the restoration of the Kibale National Park were the feeding guilds and morphological traits of birds were gathered from observed specimens in different aged forests to see if these traits change along the age gradient.  Understanding the relationship between forest age and species characteristics is crucial for effective conservation and management strategies. Conservation efforts often involve maintaining or restoring habitat conditions that support key species populations, which may include managing forest age structure to meet specific ecological requirements. By examining the data and working the statistics, significance could be found in all cases regarding bird traits and total number of individuals, with an increase in variables when compared to forest of primary age. Significance was only found in insectivore/nectivorous (IN) feeding guild with significance difference between forests of younger-primary age and older-primary age, and the sallying insectivorous (SAL) feeding guilds with no significant difference between the forest ages.

Examination of bird assemblages along an environmental gradient which encompasses both climate and habitat change is needed if we are to better understand the potential effects of these changes for avians and the ecological process that depend upon them. Climate change is predicted to have a significant impact on deserts and desert margins, resulting in distributional shifts of entire ecosystems and new community associations. This study explores the probable responses of avian communities to increasing desertification. In general, species richness and numbers of birds in arid zones are low compared to more mesic areas. Different combinations of habitat types and the variety of patches in a landscape influence the diversity and community structures of avians in that landscape. The role of vegetation structure in avian habitat selection in semi-arid areas is dictated by horizontal habitat density as well as vertical structure. Although bird distribution is determined by habitat boundaries, most birds are flexible and can disperse across small habitat barriers. The hypothesis tested, was that bird species assemblages along an aridity gradient are affected primarily by rainfall and secondarily by habitat type. Assessing the impacts of rainfall and habitat on bird variables, such as species richness, abundance, diversity, biomass, and life history traits, were the objectives of the study. An east-west aridity gradient of 300 mm, stretching over 370 km, was chosen in central Namibia for the study area. The climate is harsh with localised rain and considerable daily fluctuations in temperature. Grasses, and trees and shrubs up to 7 m in height are the co-dominant life-forms. Surveys were conducted over three years; one winter and one summer survey in each year. Rainfall, seasons and vegetation height were recorded as environmental variables. Three structurally different habitat types were selected for stratified sampling: open areas, rivers and thickets. Open areas were dominated by grass; river refers to ephemeral dry river lines with mature trees; and thickets comprise woody shrubs and trees. At each site, the same three habitats were used for bird sampling, resulting in 15 sample units. Sampling took place on 51 discontinuous line transects of 1km in length and without a width limit. Univariate analyses included ANOVA and t-tests. Multivariate analyses consisted of cluster analysis, MRPP tests, indicator analysis, Shannon diversity index and NMS ordinations. NMS bi-plots were used to define avian community structures responding to aridity, habitat, migration and life history traits. The results showed that bird species richness, abundance, and diversity remained relatively constant across the aridity gradient, until they declined significantly once a certain aridity threshold was crossed at the most arid site. There were significantly more bird species and individual birds at the wetter sites than at the drier sites. Rivers contained more birds than thickened or open habitat types, suggesting the importance of riparian habitat types for maintaining avian diversity. The three more mesic sites included higher numbers of species from the nesting and feeding guilds, regardless of habitat type, than the two more arid sites. The aridity threshold had a significant effect on bird community structures: more migrant and nomadic species, and omnivore and insectivore species persisted in very arid conditions. From the results it was predicted that climate change will cause avian species to undergo range shifts from west to east, resulting in community composition changes and a reduction in diversity. Life history traits affect the adaptive capabilities of bird species and it is predicted that nomadism, flexibility in diet, and adaptability of nesting requirements will contribute to species persistence in the drier conditions predicted under current climate change scenarios. Dry river lines will act as refugia for avian diversity, but crucial habitat types that currently contain less diversity are also important for maintaining unique avian assemblages. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Examination of bird assemblages along an environmental gradient which encompasses both climate and habitat change is needed if we are to better understand the potential effects of these changes for avians and the ecological process that depend upon them. Climate change is predicted to have a significant impact on deserts and desert margins, resulting in distributional shifts of entire ecosystems and new community associations. This study explores the probable responses of avian communities to increasing desertification. In general, species richness and numbers of birds in arid zones are low compared to more mesic areas. Different combinations of habitat types and the variety of patches in a landscape influence the diversity and community structures of avians in that landscape. The role of vegetation structure in avian habitat selection in semi-arid areas is dictated by horizontal habitat density as well as vertical structure. Although bird distribution is determined by habitat boundaries, most birds are flexible and can disperse across small habitat barriers. The hypothesis tested, was that bird species assemblages along an aridity gradient are affected primarily by rainfall and secondarily by habitat type. Assessing the impacts of rainfall and habitat on bird variables, such as species richness, abundance, diversity, biomass, and life history traits, were the objectives of the study. An east-west aridity gradient of 300 mm, stretching over 370 km, was chosen in central Namibia for the study area. The climate is harsh with localised rain and considerable daily fluctuations in temperature. Grasses, and trees and shrubs up to 7 m in height are the co-dominant life-forms. Surveys were conducted over three years; one winter and one summer survey in each year. Rainfall, seasons and vegetation height were recorded as environmental variables. Three structurally different habitat types were selected for stratified sampling: open areas, rivers and thickets. Open areas were dominated by grass; river refers to ephemeral dry river lines with mature trees; and thickets comprise woody shrubs and trees. At each site, the same three habitats were used for bird sampling, resulting in 15 sample units. Sampling took place on 51 discontinuous line transects of 1km in length and without a width limit. Univariate analyses included ANOVA and t-tests. Multivariate analyses consisted of cluster analysis, MRPP tests, indicator analysis, Shannon diversity index and NMS ordinations. NMS bi-plots were used to define avian community structures responding to aridity, habitat, migration and life history traits. The results showed that bird species richness, abundance, and diversity remained relatively constant across the aridity gradient, until they declined significantly once a certain aridity threshold was crossed at the most arid site. There were significantly more bird species and individual birds at the wetter sites than at the drier sites. Rivers contained more birds than thickened or open habitat types, suggesting the importance of riparian habitat types for maintaining avian diversity. The three more mesic sites included higher numbers of species from the nesting and feeding guilds, regardless of habitat type, than the two more arid sites. The aridity threshold had a significant effect on bird community structures: more migrant and nomadic species, and omnivore and insectivore species persisted in very arid conditions. From the results it was predicted that climate change will cause avian species to undergo range shifts from west to east, resulting in community composition changes and a reduction in diversity. Life history traits affect the adaptive capabilities of bird species and it is predicted that nomadism, flexibility in diet, and adaptability of nesting requirements will contribute to species persistence in the drier conditions predicted under current climate change scenarios. Dry river lines will act as refugia for avian diversity, but crucial habitat types that currently contain less diversity are also important for maintaining unique avian assemblages. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-03-23T20:53:27Z No. of bitstreams: 1 LianaMPC_DISSERT.pdf: 2474434 bytes, checksum: f2bb5ffb379f9469038f03a2e7fdd955 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:58:23Z (GMT) No. of bitstreams: 1 LianaMPC_DISSERT.pdf: 2474434 bytes, checksum: f2bb5ffb379f9469038f03a2e7fdd955 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:58:34Z (GMT) No. of bitstreams: 1 LianaMPC_DISSERT.pdf: 2474434 bytes, checksum: f2bb5ffb379f9469038f03a2e7fdd955 (MD5) / Made available in DSpace on 2017-04-13T14:58:44Z (GMT). No. of bitstreams: 1 LianaMPC_DISSERT.pdf: 2474434 bytes, checksum: f2bb5ffb379f9469038f03a2e7fdd955 (MD5) Previous issue date: 2016-03-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In semiarid regions, as the Caatinga, the rains distribution can determine the food availability and the intensity of hydric stress. This, with frequency, affects breeding aspects of birds, as time, length and reproduction intensity. In this study we have tested the hypothesis: (1) The breeding of the sampled species is restricted to the rainy season characteristic of the region; (2) Intra-annual variations in the rains’ volume and frequency are correlated with the quantity of individuals and species reproducing; (3) the species of the community reproducing in a way temporally jointly, independent of the feeding guilds. The study was accomplished in Caatinga’s region, with assessments every 14 days of brood patch occurrence. Three reproductive cycles was studied between september-2012 and october-2015. It was utilized the Cross-Correlation Function – CCF to verify the relation existing between the rains and the breeding birds. Altogether, 46 species (377 records) were observed with patches. The reproduction occurred in a seasonal way between february and july, with 94% of the records of patches restricted to the period. The intensity and duration of the breeding (total of individuals and species) was significantly correlated with the rains, when considered the time lag of 14 days. The length (140, 168, and 154 days) and time (march/02 to july/20, February/01 to july/19, February/12 to july/18) of breeding differed between three reproductive cycles. The analysis by feeding guild (insectivore-restrictive, insectivore-frugivorous, insectivore-granivorous and omnivorous) resulted in a similar pattern to general, mainly when it’s considered the correlation and time lag with the rains. Our study indicates that the breeding birds in the Caatinga’s area studied it was not just, generally, related to rainy seasons, as it was break out via answer of short deadline to the rainfall intensity. Including having it period, length and intensity regulated by this climatic factor or by other factors correlated to rains (g.e. food availability) / Em regiões semiáridas, como a Caatinga, a distribuição das chuvas pode determinar a disponibilidade do alimento e a intensidade do estresse hídrico. Isso, com frequência, afeta aspectos reprodutivos das aves, tais como época, comprimento e intensidade da reprodução. Neste estudo, testamos as hipóteses: (1) A reprodução das espécies amostradas é restrita ao período chuvoso característico da região; (2) variações intra-anuais no volume e na frequência das chuvas estão correlacionadas com a quantidade de indivíduos e espécies se reproduzindo; (3) as espécies da comunidade se reproduzem de forma temporalmente conjunta, independentemente da guilda alimentar. O estudo foi realizado em uma região de Caatinga, com avaliações a cada 14 dias de ocorrência de placa de incubação. Três ciclos reprodutivos foram estudados entre set-2012 e out-2015. Foi utilizada a Função de Correlação Cruzada (Cross-correlation Function – CCF) para verificar a existência de relação entre as chuvas e a reprodução das aves. Ao todo, 46 espécies (377 registros) foram observadas com placas. A reprodução ocorreu de forma sazonal entre fevereiro e julho, com 94% dos registros de placas restritos ao período. A intensidade e a duração da reprodução (total de indivíduos e de espécies) foram significativamente correlacionadas com as chuvas, quando considerado o time lag de 14 dias. O comprimento (140, 168 e 154 dias) e a época (02/mar a 20/jul, 01/fev a 19/jul, 13/fev a 18/jul) da reprodução diferiram entre os três ciclos reprodutivos. As análises por guilda alimentar (insetívoro-restritivo, insetívoro-frugívoro, insetívoro-granívoros e onívoros) resultaram em padrão semelhante ao geral, principalmente quando considerada a correlação e time lag com as chuvas. Nosso estudo indica que a reprodução das aves na área de Caatinga estudada não só esteve, de modo geral, relacionada às épocas chuvosas, como foi deflagrada via resposta de curto prazo à intensidade da precipitação. Inclusive, tendo seus períodos, comprimentos e intensidades regulados por este fator climático ou por outros fatores correlacionados às chuvas (e.g. disponibilidade de alimento) / 2017-03-23

Les sols représentent environ 63% des émissions de N2O et à eux seuls les sols tropicaux représentent 23% de ce budget soit une contribution bien plus élevé que les sols tempérés. Ces sols sont connus pour abriter une grande biodiversité d'invertébrés dominés par quatre types i.e. termites, vers de terre, fourmis et larves de scarabaeid. Ces groupes macrofaunal sont considérés comme des ingénieurs des sols via notamment leurs actions de régulation de la disponibilité des ressources chimiques, tels que l'azote minéral pour les micro-organismes. Cette régulation est due à leurs capacités de digestion spécifiques de la matière organique ainsi que la création et/ou la modification des habitats des sols. Cette étude est basée sur l'hypothèse suivante (i) l'environnement digestif et les structures biogéniques de ces ingénieurs du sol sont considérées comme des « hot spot » d' émissions de N2O (ii) les taux d'émission de N2O varient en fonction de leurs régimes alimentaires, cette macrofaune ingérant des substrats avec différents C:N (iii) le taux d'émission de N2O de chaque invertébré est corrélé à la densité des communautés bactériennes digestives impliquées dans l'émission de N2O (bactéries nitrifiantes et dénitrifiantes) et à leur teneur en azote minéral dans leur tube digestif. Pour évaluer ces différentes hypothèses, des mesures des taux d'émission de N2O ont été effectuées in vitro en aérobiose pour la macrofaune (30 espèces différentes en provenance d'Afrique, d'Amérique du Sud et d'Europe) et leurs matériels biogéniques associées (nids, turricules). L'abondance des gènes fonctionnelles des bactéries nitrifiantes (AOA et AOB) et dénitrifiantes (nirK, nirS, nosZ) ont été quantifiés par PCR quantitative. Les termites humivores et champignonnistes ainsi que les larves de scarabaeid émettent des quantités significatives de N2O alors que les fourmis n'en émettent pas. Quand aux termites xylophages et litièrivore, ils absorbent le N2O. Les structures biogéniques des vers de terre (turricules) et des fourmis (nid) émettent des quantités importantes de N2O ce qui n'est pas le cas des nids de termites. La faune du sol et leurs structures biogéniques associées, sont donc, dans la majorité des cas étudiés, un lieu d'émission de N2O, confirmant ainsi notre première hypothèse. Ce travail a également démontré qu'il y a avait une étroite corrélation entre régime alimentaire et intensité de l'émission de N2O au sein de chaque type de macrofaune étudié. En revanche, l'abondance des gènes des communautés digestive nitrifiantes et dénitrifiantes et le contenu en N minéral au sein du tube digestif ne semblent pas être des proxies pertinents des émissions de N2O. A partir de ces mesures, des calculs ont été effectuées pour déterminer l'importance de ces émissions à l'échelle des écosystèmes tropicaux étudiés (forêt et savane). Ces calculs suggèrent que la macrofaune du sol dans ces écosystèmes pourrait contribuer entre 0,1 à 11,7% et 0,1 à 8,8% du budget total des émissions de N2O, respectivement. Les résultats de ces travaux devraient contribuer à une meilleure prise en compte de la composante biotique dans la modélisation des émissions de gaz à effet de serre provenant des sols en milieu tropical. / Soils account for about 63% of N2O emissions. Tropical soils are estimated to emit 23% of global N2O emission budget which is much higher than temperate soil N2O emissions. These soils also harbor a huge biodiversity of invertebrates dominated by four types of macrofauna i.e. termites, earthworms, ants and scarabaeid grubs. These macrofaunal groups are considered as soil engineers because they regulate the availability of chemical resources, like mineral nitrogen, for the microorganisms via their specific digestion capabilities and/or by creating and modifying soil habitats. This study is based on the following hypothesis (i) the gut environment or biogenic structures of these soil engineers are considered as hotspots of N2O emission (ii) the N2O emission rates will vary according to their feeding behavior as these macrofauna thrive on diverse substrates with different C:N ratio (iii) the rate of N2O emission in each soil fauna will also depend on the gut density of the bacterial communities involved in the N2O emission (nitrifiers and denitrifiers) and on the mineral nitrogen content within the gut. To assess these different hypotheses in-vitro short-term N2O emission rates were assessed for either live macrofauna (30 species collected from Africa, South America and Europe) or their biogenic materials or both under aerobic incubations. Genes abundance of nitrifiers (AOA and AOB) and denitrifiers (nirK, nirS, nosZ) were quantified by real time quantitative PCR. Soil-feeders and fungus-growing termites and scarabaeid grubs emitted in-vivo N2O while ants did not. Surprisingly, wood- and grass-feeding termites revealed an uptake of N2O. Biogenic structures of earthworms and ants emitted substantial amount of N2O while those of termites did not. The emission difference between macrofauna or their biogenic materials and their control materials was significant for most of the macrofaunal groups studied confirming our first hypothesis. We also confirmed that the feeding behavior (total N content and C:N ratio of food material) is the main factor explaining the observed N2O emission pattern of each macrofaunal group investigated whereas genes abundances, particularly of denitrifiers and gut N mineral content did not appear to be relevant proxies of the N2O emissions rates. A back-on-the-envelope data upscaling suggests that soil macrofauna could contribute from 0.1–11.7% and 0.1–8.8% of the total soil N2O emissions, respectively, for the tropical rainforest and dry savanna ecosystems. This work should contribute to a better estimation of the soil biotic compartment in the different models of greenhouse gas emissions from tropical soils.

El objetivo de esta tesis es estudiar el efecto del enriquecimiento por materia orgánica producida por el cultivo de peces en el mar y por los vertidos de petróleo en el medio marino. Este trabajo intenta explicar las consecuencias ecológicas de los impactos generados por este tipo de contaminación, y en diseñar de test de toxicidad para evaluar la contaminación en el sur de las costas europeas. Específicamente, en relación con el impacto de la acuicultura, los estudios de recuperación durante la Apertura de peces bentónicos de reducción de piscicultura marina, el papel de la depredación en el sistema bentónico dispersión de los residuos y los vínculos horizontales y verticales con un impacto bentónico. / The aim of this thesis is to study the effect of organic matter enrichment produced by marinefinfish farming and oil spills on the marine environment. This work is focused on elucidating theecological consequences of the impact generated by this type of pollution, and on designingtoxictity tests to evaluate pollution for southern European coasts. Specifically, related with aquaculture impact, it studies benthic recovery during open sea fish farming abatement, the role of predation in the benthic system and links horizontal and vertical waste dispersion with benthic impact.