A expansão da agricultura tem levado a utilização intensiva de agrotóxicos para o controle de pragas agrícolas que apresentam sérios riscos de contaminação tanto de ambientes aquáticos como terrestres. A contaminação da biota do solo pode causar efeitos sobre diversos processos ecossistêmicos tendo em vista a importância que estes organismos desempenham na estrutura do solo. O objetivo dessa pesquisa foi avaliar os possíveis efeitos do inseticida/acaricida Kraft 36EC sobre a composição da fauna edáfica total e sobre a composição da comunidade de colêmbolos utilizando os atributos funcionais, em uma escala temporal, durante dois períodos amostrais. De forma geral, ambas as estações apresentaram diferenças na composição da fauna edáfica ao longo do tempo, nos dois tratamentos. Os colêmbolos foram os organismos mais sensíveis ao inseticida. As variáveis ambientais (temperatura e umidade) influenciaram nos efeitos do inseticida/acaricida sobre os organismos, principalmente em situações extremas. Os índices de diversidade [média por atributo (mT) e diversidade funcional (FD)] com as morfoespécies de colêmbolos, demostraram que o inseticida acaricida reduziu a diversidade funcional. Tais resultados estavam relacionados com a dominância de espécies epiedáficas (superficiais), em relação as hemiedáficas (mais afetadas pelo inseticida), principalmente no vigésimo primeiro dia. A atividade alimentar (teste bait lamina) foi reduzida ao longo do período de exposição. Os resultados obtidos mostraram que mesmo em doses recomendadas o inseticida/acaricida afetou a composição da fauna edáfica. Além disso, esse trabalho demonstrou a importância de pesquisas que avaliam não apenas dados taxonômicos como também a estrutura funcional das comunidades edáficas. Nesse sentido, podemos predizer possíveis alterações dos agrotóxicos sobre os processos ecossistêmicos. / The expansion of agriculture has led to the intensive use of pesticides for the control of agricultural pests that present serious risks of contamination in both aquatic and terrestrial environments. Contamination of soil biota by these pollutants can have effects on various ecosystem processes in view of the importance that these organisms play in the soil structure. The objective of this research was to evaluate the possible effects of the acaricide insecticide Kraft 36EC on the composition of the total soil fauna and on the composition of the community of collembolans using the functional traits, over time, during the dry and rainy season. In general, there are differences in the composition of the edaphic fauna over time, in both treatments. The collembolans were the most sensitive to insecticidal organisms. Environmental variables can influence the effects on organisms, especially in extreme situations.The diversity index [average per attribute (mT) and functional diversity (FD)] with morphospecies collembolan, showed that the insecticide reduced functional diversity. These results were related to the dominance of epiedaphic species (surface), in relation to hemiedaphic (more affected by insecticide), especially in the twenty-first day. Feeding activity (test blade bait) was reduced over the exposure period. The results showed that even at recommended doses the insecticide affected the composition of the edaphic fauna. In addition, this work has demonstrated the importance of research that evaluates not only taxonomic data but also the functional structure of edaphic communities. In this way, it is possible to predict possible changes in agrochemicals on ecosystem processes.

Traditionally, hypoxia has been defined as the situation where DO levels have fallen below 2.0 mg O2 L-1, but increasing evidence suggests that this low level of DO is inadequate to describe the onset of hypoxia impacts for many organisms. Consequently, there is a need for a greater understanding of how ‘moderate’ alterations in DO levels will affect ecosystem processes and functionality, specifically through behavioural and physiological alterations at the organism and community level. This thesis reports on mesocosm experiments which were conducted to examine the effects of moderate ( > 3.0 mg O2 L-1) hypoxia on firstly, a key ecosystem engineer, the brittlestar Amphiura filiformis, and secondly, on the Station L4 infaunal macrobenthic community. Station L4 is a longstanding marine biodiversity and MSFD reference site and forms part of the Western Channel Observatory. At the organism level, short-term (14 d) exposure to moderate hypoxia significantly reduced oxygen uptake rates, oocyte diameter and oocyte development in A. filiformis. However, these physiological affects occurred irrespective of brittlestar population density. Additionally, moderate hypoxia reduced brittlestar activity, in terms of bioturbation behaviour, consequentially having an effect on ammonium and silicate fluxes. These observations were only detected when brittlestar population density was high. It was concluded that denser populations of A. filiformis may therefore exhibit the greatest changes in behaviour and shifts in ecosystem function as competition for resources and oxygen heightens. The benthic community at Station L4, displayed considerable tolerance to medium-term (6 wk.) exposure to moderate hypoxia, in terms of structure, diversity and bioturbatory behaviour, but these results may be different if exposure was longer or more severe. Alterations in nutrient fluxes were detected, but there was little evidence to suggest these changes were due to macrofaunal behavioural alterations. Additionally, results from this study revealed that bringing complex natural communities into the mesocosm caused a substantial loss of individuals and species, mainly due to translocation and disturbance effects. This important insight into the effects of bringing community assemblages into the mesocosm confirms that even with a loss of diversity, the L4 community maintained functionality and was resilient to alterations in DO. This suggests that the L4 benthic community does not depend on any one specific species for the provision of important ecosystem processes, resulting in considerable functional resilience within the L4 system. However, vulnerability to benthic systems may increase if functionality is dominated by species such as A. filiformis. Consequently, moderate hypoxia may not immediately affect benthic communities in terms of structure and diversity, but the physiological effects on individuals, especially to reproductive development, may cause alterations in the quality and quantity of planktonic propagules supplied by benthic species to the pelagic environment. This could affect benthic community diversity and functionality in the long term if repeated hypoxic events occur.

Atualmente a maior ameaça à integridade de ecossistemas aquáticos reside nas ações antrópicas, que através de alterações na cobertura vegetal ripária, atingem todos os compartimentos dos sistemas lóticos, alterando a estrutura física, química e biológica do rio e os padrões de ligação entre ecossistemas terrestres e aquáticos. A importância dos macroinvertebrados fragmentadores ainda não é bem conhecida nos trópicos. Eles podem contribuir para a decomposição de folhas em córregos, que é um processo fundamental para o fluxo de energia em rios de pequeno porte. Os processos de decomposição e produção secundária de macroinvertebrados aquáticos nos ecossistemas lóticos são intimamente relacionados com o aporte da vegetação terrestre, e podem ser sensíveis às alterações na cobertura vegetal ripária. Os objetivos desse estudo foram avaliar: (a) quais mudanças o desmatamento pode causar nos parâmetros físicos e químicos de rios; (b) os efeitos do desmatamento sobre a estrutura da comunidade de macroinvertebrados bentônicos associados às folhas, (c) nos processos ecossistêmicos, como decomposição foliar e produção secundária, e (d) a associação entre produção secundária de fragmentadores e decomposição foliar. O estudo foi realizado em 27 locais distribuídos em quatro córregos (7-8 locais por rio) de segunda-terceira ordem e que apresentavam um gradiente de desmatamento. Para estimar a taxa de decomposição, cinco pacotes de folha foram imersos em cada um dos pontos. Um pacote de folha foi retirado de cada ponto após 2, 7, 15 e 28 dias de imersão. O quinto pacote de folha foi retirado no 37 dia de imersão para as estimativas de produção secundária, biodiversidade e a diversidade funcional de insetos aquáticos. As concentrações de amônio aumentaram e a riqueza de espécies de insetos aquáticos e de EPTs (Ephemeroptera, Plecoptera e Trichoptera) dos pacotes de folhas diminuíram com o aumento do desmatamento. As taxas de decomposição diminuíram com o aumento do desmatamento. Os dados sugerem que a perda de vegetação ripária pela conversão em agropecuária teve impacto em parâmetros químicos e bióticos, tanto na estrutura da comunidade de macroinvertebrados quanto no funcionamento do ecossistema. Concluímos que a restauração e preservação da mata ripária deve ser um foco central das estratégias de gestão de ecossistemas lóticos para assegurar que os processos ecossistêmicos e a estrutura das comunidades em bacias hidrográficas estejam agindo como provedores dos serviços ambientais esperados. / Currently the biggest threat to the integrity of aquatic ecosystems lies in human actions, which through changes in riparian vegetation, reach all compartments of river systems by changing the physical structure, chemical and biological river and connecting patterns between terrestrial ecosystems and water. Macroinvertebrate shredders importance is not well known in the tropics. They can contribute to leaf decomposition in streams, which is a fundamental process for energy flow in small rivers. Leaf decomposition and aquatic macroinvertebrates secondary production processes in stream ecosystems are closely related to the contribution of terrestrial vegetation, and may be sensitive to changes in riparian vegetation. The objectives of this study were to assess: (a) what changes deforestation can cause the physical and chemical parameters of rivers; (B) the effects of deforestation on benthic macroinvertebrate community structure associated with leaves, (c) the effects of deforestation in ecosystem processes such as leaf decomposition and secondary production, and (d) the association between shredders secondary production and leaf decomposition. The study was conducted in 27 sites distributed in four streams (7-8 sites per river) from second to third order that had deforestation gradient. To estimate decomposition rates five leaf packs were immersed in each of the points. A leaf pack was removed from each after 2, 7, 15 and 28 days of immersion. The fifth leaf pack was removed on the 37th day of immersion to estimates of secondary production, biodiversity and functional diversity of aquatic insects. The ammonium concentrations increased and species richness of aquatic insects and EPT (Ephemeroptera, Plecoptera and Trichoptera) of leaf packs decreased with increase of deforestation. The decomposition rates decreased with increasing deforestation. The data suggest that the loss of riparian vegetation in the agricultural conversion impacted chemical and biotic parameters in both macroinvertebrate community structure and the functioning of the ecosystem. We conclude that the restoration and preservation of riparian vegetation must be a central focus of stream ecosystems management strategies to ensure that ecosystem processes and community structure in river basins are acting as providers of the expected environmental services.

Atualmente a maior ameaça à integridade de ecossistemas aquáticos reside nas ações antrópicas, que através de alterações na cobertura vegetal ripária, atingem todos os compartimentos dos sistemas lóticos, alterando a estrutura física, química e biológica do rio e os padrões de ligação entre ecossistemas terrestres e aquáticos. A importância dos macroinvertebrados fragmentadores ainda não é bem conhecida nos trópicos. Eles podem contribuir para a decomposição de folhas em córregos, que é um processo fundamental para o fluxo de energia em rios de pequeno porte. Os processos de decomposição e produção secundária de macroinvertebrados aquáticos nos ecossistemas lóticos são intimamente relacionados com o aporte da vegetação terrestre, e podem ser sensíveis às alterações na cobertura vegetal ripária. Os objetivos desse estudo foram avaliar: (a) quais mudanças o desmatamento pode causar nos parâmetros físicos e químicos de rios; (b) os efeitos do desmatamento sobre a estrutura da comunidade de macroinvertebrados bentônicos associados às folhas, (c) nos processos ecossistêmicos, como decomposição foliar e produção secundária, e (d) a associação entre produção secundária de fragmentadores e decomposição foliar. O estudo foi realizado em 27 locais distribuídos em quatro córregos (7-8 locais por rio) de segunda-terceira ordem e que apresentavam um gradiente de desmatamento. Para estimar a taxa de decomposição, cinco pacotes de folha foram imersos em cada um dos pontos. Um pacote de folha foi retirado de cada ponto após 2, 7, 15 e 28 dias de imersão. O quinto pacote de folha foi retirado no 37 dia de imersão para as estimativas de produção secundária, biodiversidade e a diversidade funcional de insetos aquáticos. As concentrações de amônio aumentaram e a riqueza de espécies de insetos aquáticos e de EPTs (Ephemeroptera, Plecoptera e Trichoptera) dos pacotes de folhas diminuíram com o aumento do desmatamento. As taxas de decomposição diminuíram com o aumento do desmatamento. Os dados sugerem que a perda de vegetação ripária pela conversão em agropecuária teve impacto em parâmetros químicos e bióticos, tanto na estrutura da comunidade de macroinvertebrados quanto no funcionamento do ecossistema. Concluímos que a restauração e preservação da mata ripária deve ser um foco central das estratégias de gestão de ecossistemas lóticos para assegurar que os processos ecossistêmicos e a estrutura das comunidades em bacias hidrográficas estejam agindo como provedores dos serviços ambientais esperados. / Currently the biggest threat to the integrity of aquatic ecosystems lies in human actions, which through changes in riparian vegetation, reach all compartments of river systems by changing the physical structure, chemical and biological river and connecting patterns between terrestrial ecosystems and water. Macroinvertebrate shredders importance is not well known in the tropics. They can contribute to leaf decomposition in streams, which is a fundamental process for energy flow in small rivers. Leaf decomposition and aquatic macroinvertebrates secondary production processes in stream ecosystems are closely related to the contribution of terrestrial vegetation, and may be sensitive to changes in riparian vegetation. The objectives of this study were to assess: (a) what changes deforestation can cause the physical and chemical parameters of rivers; (B) the effects of deforestation on benthic macroinvertebrate community structure associated with leaves, (c) the effects of deforestation in ecosystem processes such as leaf decomposition and secondary production, and (d) the association between shredders secondary production and leaf decomposition. The study was conducted in 27 sites distributed in four streams (7-8 sites per river) from second to third order that had deforestation gradient. To estimate decomposition rates five leaf packs were immersed in each of the points. A leaf pack was removed from each after 2, 7, 15 and 28 days of immersion. The fifth leaf pack was removed on the 37th day of immersion to estimates of secondary production, biodiversity and functional diversity of aquatic insects. The ammonium concentrations increased and species richness of aquatic insects and EPT (Ephemeroptera, Plecoptera and Trichoptera) of leaf packs decreased with increase of deforestation. The decomposition rates decreased with increasing deforestation. The data suggest that the loss of riparian vegetation in the agricultural conversion impacted chemical and biotic parameters in both macroinvertebrate community structure and the functioning of the ecosystem. We conclude that the restoration and preservation of riparian vegetation must be a central focus of stream ecosystems management strategies to ensure that ecosystem processes and community structure in river basins are acting as providers of the expected environmental services.

A expansão da agricultura tem levado a utilização intensiva de agrotóxicos para o controle de pragas agrícolas que apresentam sérios riscos de contaminação tanto de ambientes aquáticos como terrestres. A contaminação da biota do solo pode causar efeitos sobre diversos processos ecossistêmicos tendo em vista a importância que estes organismos desempenham na estrutura do solo. O objetivo dessa pesquisa foi avaliar os possíveis efeitos do inseticida/acaricida Kraft 36EC sobre a composição da fauna edáfica total e sobre a composição da comunidade de colêmbolos utilizando os atributos funcionais, em uma escala temporal, durante dois períodos amostrais. De forma geral, ambas as estações apresentaram diferenças na composição da fauna edáfica ao longo do tempo, nos dois tratamentos. Os colêmbolos foram os organismos mais sensíveis ao inseticida. As variáveis ambientais (temperatura e umidade) influenciaram nos efeitos do inseticida/acaricida sobre os organismos, principalmente em situações extremas. Os índices de diversidade [média por atributo (mT) e diversidade funcional (FD)] com as morfoespécies de colêmbolos, demostraram que o inseticida acaricida reduziu a diversidade funcional. Tais resultados estavam relacionados com a dominância de espécies epiedáficas (superficiais), em relação as hemiedáficas (mais afetadas pelo inseticida), principalmente no vigésimo primeiro dia. A atividade alimentar (teste bait lamina) foi reduzida ao longo do período de exposição. Os resultados obtidos mostraram que mesmo em doses recomendadas o inseticida/acaricida afetou a composição da fauna edáfica. Além disso, esse trabalho demonstrou a importância de pesquisas que avaliam não apenas dados taxonômicos como também a estrutura funcional das comunidades edáficas. Nesse sentido, podemos predizer possíveis alterações dos agrotóxicos sobre os processos ecossistêmicos. / The expansion of agriculture has led to the intensive use of pesticides for the control of agricultural pests that present serious risks of contamination in both aquatic and terrestrial environments. Contamination of soil biota by these pollutants can have effects on various ecosystem processes in view of the importance that these organisms play in the soil structure. The objective of this research was to evaluate the possible effects of the acaricide insecticide Kraft 36EC on the composition of the total soil fauna and on the composition of the community of collembolans using the functional traits, over time, during the dry and rainy season. In general, there are differences in the composition of the edaphic fauna over time, in both treatments. The collembolans were the most sensitive to insecticidal organisms. Environmental variables can influence the effects on organisms, especially in extreme situations.The diversity index [average per attribute (mT) and functional diversity (FD)] with morphospecies collembolan, showed that the insecticide reduced functional diversity. These results were related to the dominance of epiedaphic species (surface), in relation to hemiedaphic (more affected by insecticide), especially in the twenty-first day. Feeding activity (test blade bait) was reduced over the exposure period. The results showed that even at recommended doses the insecticide affected the composition of the edaphic fauna. In addition, this work has demonstrated the importance of research that evaluates not only taxonomic data but also the functional structure of edaphic communities. In this way, it is possible to predict possible changes in agrochemicals on ecosystem processes.

The Effects of Tropical Forest Management on Biodiversity and Ecosystem Functioning Eleanor M. Slade 1. Between 35 % and 50 % of all closed-canopy tropical forest has been lost, and the rate of deforestation continues to increase throughout the tropics. Despite a wealth of literature on the effects of tropical forest disturbance on the diversity and composition of a variety of taxa, there is still no clear consensus on the value of disturbed forests for biodiversity. 2. If forest management practises are to be sustainable in the long-term they should maintain both biodiversity and ecosystem functioning (the interactions and processes of the ecosystem), as well as a timber harvest. However, few studies have investigated the extent to which ecosystem functioning is reduced in logged forests. The effects of different logging intensities on a variety of taxa, and the ecosystem processes with which they are associated, were assessed in the Danum Valley Conservation Area in Sabah (Malaysian Borneo). 3. Even under high logging intensities, the forests of Sabah appear to have been managed in a way that maintains timber yields in the short-term. However, other aspects of forest structure had been affected, which could have important consequences ecologically, and for the long-term sustainability of timber harvests. 4. Combining field studies with manipulative experiments allows assessment of the impacts of species changes associated with habitat modification on measures of ecosystem functioning. Dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) functional group richness and composition were manipulated in a series of field experiments. Certain functional groups and species were found to have a greater impact on ecosystem functioning than others; nevertheless a full complement of species was needed to maintain full ecosystem functioning. 5. Dung beetles appeared to be relatively robust to changes in forest structure associated with selective logging, but species richness was reduced with high-intensity logging. There was a corresponding decrease in ecosystem functioning (dung and seed removal) with a decrease in species richness, and a decrease in the biomass of large nocturnal tunnellers, suggesting that although some species are dominant, rare species are also needed to preserve full ecosystem functioning. 6. A complex interaction between birds and ants resulted in reduced herbivory of seedlings of the important timber tree, Parashorea malaanonan, in some instances. However, this interaction was not affected by either selective or high intensity logging. Seedfall of P. malaanonan, was reduced in logged forest compared to primary forest. Despite insect seed predation being higher in primary forest, there was still successful recruitment during a non-mast year. Parasitism of insect-predated seeds was found to be inversely density dependent, and was higher in logged forest where seed predation was lower. 7. The results of this thesis suggest that the forests of Sabah appear to be being logged under a management system that is compatible with sustainable timber management, but not necessarily sustainable forest management. Low intensity selective logging seems to preserve much of the original forest structure, biodiversity and ecosystem functioning compared to logging at higher intensities. However, ecosystem processes were variable in their response to logging, suggesting that management decisions should be based on the consideration of multiple taxa and processes.

No description available.

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No. of bitstreams: 2 Dissertação - Oscar Daniel Plazas Jiménez - 2018.pdf: 5372786 bytes, checksum: ccb044675f67ad084ee0892aa9c09bae (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-03-06 / Theoretical and empirical evidence suggest that the mass ratio and the niche complementarity hypothesis are able to explain how species trait composition drives decomposition, an ecosystem process related with nutrient cycling and carbon sequestration. These two hypotheses are respectively related with the mean trait values of individuals present in a given community and its variance. Thus, it is impossible to test them adequately without experiments planned to approach these two aspects simultaneously. Although leaf functional traits influence decomposition process, an experimental design made to disentangle the unique, combined and strength of effects of the mechanisms proposed by MRH and NCH on decomposition should use leaf functional traits as predictors, but this has not yet been done. Here, we used two leaf nutritional traits (leaf nitrogen and magnesium-calcium content) and one structural trait (specific leaf area; SLA) from 20 species of seasonal dry forest to simulate leaf mixtures with different mean trait values (calculated as community-weighted mean; CWM) and variation of trait values (functional diversity; FD). For each trait, 40 leaf mixtures with different quasi-orthogonal combinations of CWM and FD were selected and left in the field to decompose for six months. We found that MRH mechanisms exert predominant role on decomposition where low and high CWM values were related with high biomass loss. Then, this add more evidence to support that the mean trait values of leaf mixtures are the main drivers of biomass loss. Contrary to previously evidences, trait complementarity does not increase efficiency and instead, an increasing in niche complementarity (high FD values) was followed by a decreasing in biomass loss efficiency. So, this question the importance of mechanism behind NCH on leaf decomposition. Additionally, we found that whereas nutritional traits were able to predict leaf decomposition, structural traits were not, in opposite to what is reported in the literature. Our results highlight that the mean resources quality of the leaf mixtures is the main driver of biomass loss and trait complementarity does not increase efficiency of biomass loss. Due to this, we proposed that in future studies mean resources quality of the leaf mixtures will be use as parameter to test and predict the possible impacts of human-induced changes on nutrient cycling and carbon sequestration. / Evidências empíricas e teóricas sugerem que os mecanismos propostos pelas hipóteses da razão da massa e da complementaridade de nicho (HRM e HCN respectivamente) são capazes de explicar como a composição de atributos funcionais das espécies determina a decomposição, um importante processo ecossistêmico relacionado com a ciclagem de nutrientes e o sequestro de carbono. Essas duas hipóteses estão relacionadas, respectivamente, com o valor médio dos atributos das espécies presentes em uma dada assembleia ou com a sua variação. Portanto, é impossível testar adequadamente essas duas hipóteses sem experimentos planejados para abordar simultaneamente esses dois aspectos, algo que é raramente feito. Os atributos funcionais foliares apresentam forte efeito nas taxas de decomposição em ecossistemas terrestres. Assim, um desenho experimental feito para separar a magnitude relativa dos efeitos únicos e combinados da HRM e HCN sobre a decomposição de folhas deve usar atributos foliares como preditores, mas até agora isso não foi feito. Neste trabalho, simulamos misturas de folhas com diferentes valores médios ponderados pela abundância (i.e., community weighted mean, CWM) de atributos e dispersão (i.e., functional diversity; FD) destes valores para dois atributos foliares nutricionais (conteúdo de nitrogênio e conteúdo de magnésio e cálcio) e um atributo estrutural (área foliar específica; SLA) quantificados para 20 espécies de floresta estacional semidecídua. Para cada atributo, selecionamos 40 misturas de folhas com diferentes combinações quase-ortogonais de CWM e FD que posteriormente foram deixadas durante seis meses no campo para decompor. No geral, encontramos que os mecanismos propostos pela HRM têm um papel predominante na decomposição, porque altos e baixos valores de CWM estiveram relacionados com uma alta perda de biomassa. Isso adiciona mais evidência à que os valores médios dos atributos das misturas de folhas são os principais determinantes da perda de biomassa. Porém, diferente do esperado, o aumento da complementaridade dos atributos das misturas de folhas (isto é, altos 8 valores de FD) levou à uma diminuição da eficiência da perda de biomassa e não à um aumento, como era esperado. Isso coloca em questão a importância dos mecanismos propostos pela HCN na decomposição de folhas. Adicionalmente, encontramos que os atributos nutricionais foliares foram capazes de predizer a perda de biomassa enquanto que, ao contrário do reportado na literatura, o atributo estrutural SLA não teve qualquer relação com a decomposição. Nossos resultados destacam que em misturas de folhas os valores médios do conteúdo de nutrientes estão associados com as taxas de decomposição e a complementaridade dos atributos não incrementou a eficiência na perda de biomassa. Portanto, nós propomos que em estudos futuros os valores médios do conteúdo de nutrientes das misturas de folhas sejam usados como parâmetros para testar e predizer os possíveis efeitos das mudanças na biodiversidade induzidos pelo homem sobre a ciclagem de nutrientes e o sequestro de carbono

Aquatic sediments are, by surface, the largest habitat on Earth. A wide diversity of organisms inhabit these sediments and by their actions they have a large influence on and also mediate many ecosystem processes. Several of these processes, such as decomposition and remineralisation of organic matter are important on a global scale and are essential to sustain life on Earth. The main aim of this thesis was to use an experimental ecosystem ecology approach in order to study some of these ecosystem processes in marine sediments and how they are linked to biodiversity. Paper I and II found that an increased species richness of sediment deposit feeders increases the processing of organic matter from phytoplankton settled on the sea-floor, and that species-rich communities have a more efficient resource utilization of deposited organic matter. The results in paper IV and V also suggest that there is a link between microbial diversity in sediments and the degradation of organic contaminants. Paper V also shows that antibiotic pollution is a potential threat to natural microbial diversity and microbially mediated ecosystem services. The introduction of invasive species to ecosystems is another major threat to biodiversity and was studied in Paper II and III, by investigating the ecology of Marenzelleria arctia, a polychaete worm recently introduced in the Baltic Sea. Paper II suggests that M. arctia mainly utilize food resources not used by native deposit feeders, thus potentially increasing the benthic production in the Baltic Sea by increasing resource use efficiency. Paper III, however, show that M. arctia is protected from predation by the native benthic invertebrate predators, due to its ability to burrow deep in the sediment, suggesting that predation on M. arctia by higher trophic levels is restricted, thereby limiting trophic transfer. In conclusion, this thesis gives some examples of the importance of marine biodiversity for the generation of a few key ecosystem processes, such as organic matter processing and the degradation of harmful contaminants. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: In press.

Minimising the potential impact of forest management requires an understanding of the key elements that maintain forest diversity and its role in ecological processes. Invertebrates are the most diverse of all biota and play important roles in maintaining forest processes. However, little is known about invertebrates in New Zealand's beech forests or the degree to which selective beech harvest might impact on their diversity and ability to carry out ecosystem processes. Studying ecosystem responses to disturbance is considered vital for understanding how ecosystems are maintained. One of the main objectives of this research was to assess whether litter-dwelling invertebrates were susceptible to the impacts of selective harvest and, if so, whether they could be used as indicators of forest health. Changes in invertebrate diversity could have important implications for nutrient cycling and primary production in forests. Litter-dwelling invertebrates contribute to the process of decomposition by increasing the surface area of the leaves, mixing soil organic matter and by infecting leaf particles with soil microbes. This investigation into the function of invertebrates in beech forest was carried out in the context of ecological theories which relate diversity to ecosystem stability and resilience. A replicated study was established in Maruia State Forest (South Island, New Zealand) to assess the potential biotic and abiotic impacts of sustainable beech harvest. Litter-dwelling invertebrates and environmental factors were monitored during 1997, before harvest, to determine how much variability there was between study sites. Specifically, litter pH, light intensity, litter fall, litter temperature, moisture as well as invertebrate abundance and diversity were compared before and after selective harvest. On 17 January 1998, two to three trees were selectively harvested from three of the nine study sites. On 15 February 1998 a similar number of trees were winched over or felled manually to create artificial windthrow sites. The remaining three undisturbed sites were used as controls. Invertebrates belonging to the detritivore guild were assessed from litter samples and a series of litter-bags containing pre-weighed leaf litter which were placed in each of the sites to assess rates of litter decomposition. Millipedes (Diplopoda: Polyzoniidae, Schedotrigonidae, Dalodesmidae, Habrodesmidae, Sphaerotheridae), earthworms (Oligochaeta: Annelida), tipulid larvae (Diptera: Tipulidae), weevils (Coleoptera: Curculionidae), moth larvae (Lepidoptera: Oecophoridae, Tortricidae and Psychidae), slaters (Isopoda: Styloniscidae), Oribatid mites (Acarina: Cryptostigmata) and landhoppers (Crustacea: Amphipoda) were extracted from the litter-bags and their abundance and diversity was compared between the three treatments. Weight loss from the litter-bags and the carbon and nitrogen content of litter were used to measure the rate of decomposition in each treatment. An additional study investigated whether exclusion of invertebrates from leaf litter resulted in reduced rates of decomposition. The results indicated that there was an increase in light intensity and a small increase in temperature following selective harvest and artificial windthrow. There was no significant difference in litter moisture or the amount of litter fall between the treatments. Invertebrate abundances were significantly affected by season but did not appear to be affected by selective harvest or artificial windthrow. The diversity of invertebrates remained relatively constant throughout the year, as did the rate of decomposition. When invertebrates were excluded from the leaf litter there was no consequential effect on the rate of litter decomposition. This suggests that there may be compensatory mechanisms taking place between the trophic levels of the food web to maintain processes and that direct links between invertebrates and decomposition are relatively weak. In conclusion, it appears that the effects of selective beech harvest on forest-floor processes were minimal and are comparable to those created by natural windthrow disturbance. It also appears that macroclimatic effects such as seasonal climatic effects have a large effect on forest biota. As none of the invertebrates studied appeared to be detrimentally affected by selective harvest and as there was no direct link demonstrated with decomposition, it was considered inappropriate to advocate the use of this group of invertebrates as indicators of sustainable forest management. The results from this study provide information which may help inform decisions on the future management of diversity in beech forest ecosystems.