L'objectif de cette thèse est d'étudier le processus de décomposition des litières en région méditerranéenne et comment ce processus pouvait être affecté par le changement climatique. Dans un premier temps, nous avons abordé le rôle de la qualité et de la diversité des litières sur le processus de décomposition dans deux écosystèmes typiques de la région méditerranéenne française : la forêt à chêne et la garrigue à chêne kermès. Dans un second temps, nous avons étudié l'impact du changement climatique (via un stress hydrique aggravé) sur le processus de décomposition.Nous avons montré des effets de la diversité des litières sur le processus de décomposition et sur la structure des communautés d'organismes décomposeurs. Dans la forêt, les espèces compagnes de Q. pubescens favorisent la diversité et l'abondance des communautés d'organismes décomposeurs ainsi qu'un processus de décomposition plus efficace. A l'opposé, dans la garrigue, c'est l'espèce structurante qui favorise la décomposition et les décomposeurs.En ce qui concerne l'évolution de la relation diversité des litières - processus de décomposition dans un contexte de changement climatique, on observe une forte diminution des interactions synergiques en forêt (excepté à forte diversité végétale), alors qu'à l'opposé, cela entraine, en garrigue, une meilleure complémentarité entre les espèces avec une forte augmentation des effets synergiques.Mes résultats suggèrent que la diversité des communautés végétales joue un rôle important sur le processus de décomposition et mettent en avant que le maintien de cette diversité semble nécessaire dans un contexte de changement climatique. / L'objectif de cette thèse est d'étudier le processus de décomposition des litières en région méditerranéenne et comment ce processus pouvait être affecté par le changement climatique. Dans un premier temps, nous avons abordé le rôle de la qualité et de la diversité des litières sur le processus de décomposition dans deux écosystèmes typiques de la région méditerranéenne française : la forêt à chêne et la garrigue à chêne kermès. Dans un second temps, nous avons étudié l'impact du changement climatique (via un stress hydrique aggravé) sur le processus de décomposition.Nous avons montré des effets de la diversité des litières sur le processus de décomposition et sur la structure des communautés d'organismes décomposeurs. Dans la forêt, les espèces compagnes de Q. pubescens favorisent la diversité et l'abondance des communautés d'organismes décomposeurs ainsi qu'un processus de décomposition plus efficace. A l'opposé, dans la garrigue, c'est l'espèce structurante qui favorise la décomposition et les décomposeurs.En ce qui concerne l'évolution de la relation diversité des litières - processus de décomposition dans un contexte de changement climatique, on observe une forte diminution des interactions synergiques en forêt (excepté à forte diversité végétale), alors qu'à l'opposé, cela entraine, en garrigue, une meilleure complémentarité entre les espèces avec une forte augmentation des effets synergiques.Mes résultats suggèrent que la diversité des communautés végétales joue un rôle important sur le processus de décomposition et mettent en avant que le maintien de cette diversité semble nécessaire dans un contexte de changement climatique.

I investigated the effects ofhabitat loss and subsequent restoration on invertebrate community structure and ecosystem functioning in a mined peat bog in the North Island, New Zealand. In an experimental trial, the impact of peat bog habitat loss and isolation on the invertebrate community associated with Sporadanthus ferrugineus (Restionaceae) was investigated. Potted S. ferrugineus plants were exposed to invertebrates at various distances up to 800 m from an intact habitat (the presumed source population) over 18 weeks. Invertebrates rapidly colonised the experimental plants, with all major Orders and trophic groups present on Sc ferrugineus within 6 weeks. However. with increasing distance away from the undisturbed habitat, there was a significant decrease in total richness and abundance of invertebrates associated with the potted plants. Additional tests showed that even a moderate degree of isolation (i.e. greater than 400 m) from the intact habitat caused an almost complete failure of 'Batrachedra' sp. to colonise its host plant, at least in the short-term, The density of eggs and larvae, and the average larval size of 'Batrachedra' sp. (Lepidoptera: Coleophoridae) colonising Si ferrugineus plants, as well as the proportion of Si ferrugineus stems damaged by 'Batrachedra' sp. herbivory, all decreased logarithmically with increasing distance from the intact habitat. Surprisingly, though, the rate of recovery of the insect-plant interaction following experimental habitat restoration was remarkably rapid (i.e. between 3Y2 and 6 years). After just 6 years there was no significant difference in insect-plant interactions between the intact peat bog sites and any of the experimentally restored sites up to 800 m away. These results suggest that the degree of isolation from undisturbed habitat has a major impact on the rate and patterns of restoration recovery in the invertebrate community and that some insect-plant interactions can recover rapidly from habitat loss with restoration management. Restoration of mined peat bogs in northern New Zealand is initiated by establishing a native vegetation cover to minimize further peat degradation. The effects of various restoration techniques on litter decomposition, microbial community activity and beetle community composition were investigated within an experimental trial, These treatments included translocation ofpeat bog habitat (direct transfer of islands), milled peat islands with no seed and milled peat islands with seed, and were compared with an unrestored mined site and an undisturbed peat bog. In all the response variables measured, the undisturbed peat bog sites had significantly higher decomposition rates and microbial respiration rates, and significantly higher abundance and species richness of beetles than any of the restoration treatments. Inaddition, the technique used to restore mined peatlands had a significant effect on the beetle community composition and litter decomposition processes. Despite a rapid initial change in the beetle community following habitat translocation, the direct transfer islands were still the most similar in beetle species composition to the undisturbed peat bog. Microbial activity and decomposition rates were higher in the direct transfer and mined peat surface after 6 months. However, even after 12 months, decomposition rates in the restored habitats were still far from reaching the levels recorded in the undisturbed peat bog. The results suggest that beetle community structure and ecosystem processes such as decomposition and microbial activity rates may be able to recover faster with certain restoration techniques, such as direct transfer of intact habitat islands. Subsequently, I examined long-term beetle community reassembly on islands that had been restored by creating raised areas ofprocessed peat with the addition of Leptospermum scoparium seed. Monitoring of different-aged restored islands representing the full range of restoration ages (up to 6 years) available at the peat mine, indicated that as the peat islands became older and the vegetation structure became more complex, the abundance, species richness and composition of the beetle community became increasingly similar to the community in the undisturbed peat bog. Despite this, distinct differences between the intact peat bog and older restored peat islands still persisted, even after 6 years, particularly at an individual species level. However, it is predicted that within 12 years the restored peat islands will share 100% ofbeetle species in common with the undisturbed peat bog. Taken together, these results indicate that restoration is effective in initiating the recovery of beetle assemblages and ecosystem processes (such as litter decomposition and microbial community activity) in cut-over peat bogs. However, it is estimated to take at least 12 years before pre-mining communities and functions are attained, and ongoing monitoring to develop an understanding of the longer-term dynamics of such ecosystems and processes is clearly required.

Les prairies subalpines abritent de grandes populations d’herbivores sauvages et sont souvent soumises au pâturage domestique. Le but de cette thèse est d’analyser la réponse métabolique des plantes subalpines à l’herbivorie, et d’identifier les conséquences fonctionnelles sur l’écosystème via la décomposabilité des litières. Pour cela, nous avons établi un dispositif d’exclusion des herbivores sur l’alpage d’Armenaz dans le massif des Bauges, dans deux contextes de pâturage différents : extensif par des herbivores sauvages (chamois, Rupicapra rupicapra) et intensif par des herbivores domestiques (génisses, Bos taurus). Nous avons caractérisé une vingtaine d’espèces végétales par des traits fonctionnels foliaires reflétant leur métabolisme de croissance et de défense, en présence ou en absence d’herbivores, et avons estimé la décomposabilité des litières de certaines d’entre elles. Contrairement à l’hypothèse du compromis entre croissance et défense, nos résultats montrent que la présence de composés de défense (polyphénols et lignine) chez les plantes n’est pas reliée à leur stratégie d’acquisition des ressources. Dans notre étude, la réponse des plantes à l’exclusion des herbivores dépend essentiellement : (1) du contexte d’herbivorie, la réponse étant d’avantage marquée dans le contexte du pâturage intensif par les génisses qu’extensif par les chamois, (2) des espèces végétales, suggérant l’existence de différentes stratégies de défense, (3) des conditions environnementales, pouvant être le reflet d’effets d’interaction avec le traitement d’herbivorie. Parmi les réponses observées, l’exclusion des herbivores entraîne chez certaines espèces une diminution de la teneur en composés phénoliques, et plus particulièrement en flavonoïdes, pouvant refléter la relaxation de la synthèse de ces composés de résistance en absence d’herbivores. L’exclusion des chamois n’influence pas la composition chimique des litières ni leur décomposabilité. Cette dernière, parmi les composés étudiés, dépend majoritairement de sa composition en polyphénols. L’identification d’effets contrastés de différents contextes d’herbivorie sur la réponse des plantes et des fonctions écosystémiques qui en découlent nous permet d’améliorer notre compréhension du fonctionnement des prairies subalpines. Ce sont autant d’éléments pour nous aider à mieux appréhender les effets sur l’environnement d’éventuels changements démographiques des populations de grands herbivores. / Alpine grasslands are home to large populations of wild herbivores and are often exposed to additional grazing by domestic herbivores. This study aims to investigate the metabolic response of subalpine plant species to herbivory and to identify the ecosystem functional consequences via the alteration of litter decomposability. For this purpose, we set up a two-year experimental design using exclosures on the Armenaz subalpine grassland from the Bauges massif, under two mammalian herbivory regimes: intensive grazing by domestic heifers (Bos taurus) and extensive grazing by wild chamois (Rupicapra rupicapra). We measured leaf functional traits representative of growth and defense metabolisms on about twenty plant species grown in presence or absence of herbivores, and estimated litter decomposability of some of these species. Contrary to the hypothesis of a growth/defense tradeoff, our results show that the allocation of defensive compounds (polyphenols and lignin) in plants is not related to their nutrient acquisition strategy. In our study, plant responses to grazing exclusion vary according to: (1) herbivory context, plant response being more pronounced in the case of intensive grazing by heifers than extensive grazing by chamois, (2) plant species, suggesting that they rely on different defensive strategies, (3) environmental conditions, which may reflect the interactive effects with grazing treatment. One of the observed responses of plants to grazing exclusion is the decrease of their phenolic content, and more specifically flavonoids, which can be explained by the relaxation of the production of plant defenses when herbivores are no longer present. Chamois exclusion has no influence on chemical composition and decomposability of litters, the latter being best explained by its phenolic content. Revealing the contrasted effects of wild and domestic mammalian herbivores on vegetation and related soil processes allow us to improve our understanding of subalpine grasslands functioning. This should help us to better predict the effects of potential demographic variations of herbivore populations on environment.

La France compte de nombreux étangs (environ 251 000), construits le plus souvent par l’aménagement d’un barrage sur un cours d’eau de tête de bassin, dans des fonds de vallées argileux, pour la production de poissons. La Lorraine est une région riche en étangs et ces derniers sont le plus souvent localisés sur des cours d’eau temporaires dans des bassins versants agricoles et/ou forestiers. Ces cours d’eau ont un fonctionnement écologique basé sur l’intégration, par les réseaux trophiques détritiques, des ressources organiques allochtones. Or, les étangs constituent des zones lentiques biogènes : la matière organique (MO) autochtone (constituée entre autres par le plancton, les macrophytes, les fèces produits par le biote) peut modifier les équilibres – souvent fragiles – de ces écosystèmes aquatiques de tête de bassin. L’objectif de ce travail de thèse est d’étudier l’influence des étangs de barrage sur le recyclage et l’intégration de la MO allochtone et autochtone par les réseaux trophiques basaux aquatiques des cours d’eau de tête de bassin. Premièrement, ce travail a porté sur l’étude de la décomposition des litières (et des communautés associées) en amont et en aval d’étangs localisés sur des bassins soit agricoles, soit forestiers. Nos résultats mettent en exergue l’intérêt de la prise en compte de l’occupation du sol sur le bassin versant pour appréhender au mieux l’effet des étangs sur les processus de décomposition des litières. Nous montrons ainsi que l’étang de barrage entraîne une diminution de la vitesse de décomposition des litières, en lien notamment avec une diminution de la biomasse fongique, uniquement dans les cours d’eau en milieu agricole. Sur les cours d’eau forestiers, ce sont essentiellement les communautés de macroinvertébrés qui semblent influencées, et de manière plus marquée qu’en milieu agricole, avec une diminution des taxons les plus sensibles aux pollutions organiques. Puis, nous avons cherché à préciser les processus de décomposition des litières dans les cours d’eau temporaires de tête de bassin versant entravés ou non par un étang. Notre choix s’est porté sur les cours d’eau en milieu forestier afin de limiter les effets confondants liés à d’autres perturbations humaines. Dans ces conditions, nos résultats montrent que la présence d’un étang tend à augmenter la vitesse de décomposition des litières. Cela serait dû à un meilleur conditionnement des litières et également à une modification des communautés de déchiqueteurs en aval de l’étang. En revanche, l’effet de l’étang sur l’intégration des ressources allochtones par les réseaux trophiques détritiques nécessite la prise en compte des conditions hydrologiques se présentant à l’aval du barrage. Il s’agit là d’un résultat original révélant que l’impact de l’étang est plus marqué sur les communautés de déchiqueteurs et sur leur action de dégradation des litières lorsque le cours d’eau passe en régime permanent à l’aval de l’étang. Enfin, nous nous sommes intéressés à la modification des niches trophiques à partir de l’étude des signatures isotopiques des communautés de macro-invertébrés de cours d’eau entravés ou non par un étang. Nos résultats montrent que l’étang influence majoritairement les signatures isotopiques des biofilms et des matières en suspension. En lien avec cette observation, nous remarquons que les niches isotopiques des différentes guildes trophiques de macro-invertébrés sont modifiées à l’aval de l’étang. Ce résultat souligne ainsi que l’ensemble des guildes trophiques ici étudiées consomment et intègrent les ressources autochtones produites au sein même de l’étang. Pour résumer, ce travail a mis en évidence les interactions complexes entre étang et cours d’eau de tête de bassin. Il souligne de fait la nécessité de prendre en compte l’occupation du sol sur les bassins versant et le régime hydrologique du cours d’eau pour conclure sur l’effet de l’étang sur le fonctionnement écologique des cours d’eau de tête de bassin. / In France there are more than 250,000 ponds. Most often, they are dam reservoirs constructed on headwater streams in clay valleys for fish production and thus named fishponds. In Lorraine region, most of the numerous fishponds are located on temporary streams (i.e. periodically dry during summer time) in agricultural and/or forested catchments. These streams have an ecological functioning based on the integration of allochthonous organic matter (OM) resources by the basal detrital food webs. Yet, fishponds constitute biogenic lentic systems that favor autochthonous OM production (e.g. plankton, macrophytes, faeces). Consequently, fishponds could disrupt the fragile balances in these headwater stream ecosystems. The goal of my thesis was to study the effect of fishpond on the recycling and the integration of allochthonous and autochthonous OM by the aquatic food webs within headwater streams. First, we studied the litter decomposition (and the associated communities) between upstream and downstream fishponds located in agricultural or forested catchments. Our results indicate the needs to take into account the catchment land uses to grasp the fishpond effect on litter decomposition. We found that in agricultural catchments fishponds lead to a decrease of the litter breakdown rate in association with a fungal biomass decrease. In forested catchments, the macro-invertebrate assemblages are more affected than in agricultural catchments, showing a decrease of the most sensitive taxa to organic pollution. Secondly, we focused on litter processes in temporary headwater streams hampered or not by a fishpond. To this end, we worked on forest streams to exclude confounding anthropogenic effects. In this environment our results indicate that the presence of a fishpond tends to increase litter breakdown rate. It can be related with a better litter conditioning and to the shredder assemblage’s modification downstream from the fishpond. Furthermore, fishpond effect on the integration of allochthonous resources by food webs was found to be highly dependent on hydrological conditions downstream from the fishpond. This original result highlights that the impact of the fishpond seems to be greater on the shredder assemblages and on their litter breakdown activities when the stream show important hydrological modifications (i.e. become permanent downstream from the fishpond). Finally, in order to analyze the modification of trophic niches, we studied benthic macroinvertebrate isotopic signatures in streams hampered or not by a fishpond. Our results indicate that fishpond mainly influenced the isotopic signatures of biofilms and suspended OM. In line with this result, isotopic niches of the different macroinvertebrate trophic guilds are also modified downstream from the pond. Consequently we may suggest that all the studied trophic guilds consume and integrate autochthonous resources produced into the fishpond. In summary, our work highlights complex interactions between fishpond and headwater streams and underlines the needs to take into account the catchment land use and the stream hydrology before concluding on the fishpond effect on stream functioning.

Existe uma necessidade urgente em monitorar as respostas da biodiversidade e dos processos ecológicos a distúrbios e mudanças no uso da terra. Diversos estudos tem indicado que o uso da abordagem funcional da biodiversidade, baseada em atributos funcionais, facilita a compreensão sobre a organização dos organismos nas comunidades, da funcionalidade dos ecossistemas, e desta forma, auxilia na identificação das suas relações com fatores ambientais. No primeiro capítulo desta tese eu apresento o arcabouço teórico da ecologia funcional aplicada ao estudo dos invertebrados terrestres, e reviso o que são atributos funcionais, como usá-los na descrição e monitoramento das comunidades e o porquê, ressaltando a ligação dos invertebrados com processos ecológicos. Nos próximos capítulos eu apresento estudos experimentais avaliando as respostas funcionais de dois grupos de invertebrados - aranhas (Araneae) e tripes (Thysanoptera) - e de processos ecológicos influenciados por invertebrados (detritivoria e decomposição de serapilheira) ao distúrbio por fogo nos Campos Sulinos. As queimadas representam uma estratégia de manejo frequente nas pastagens naturais do RS, e carecem em estudos avaliando seus efeitos no ambiente, biodiversidade e processos. A investigação foi realizada com base em um experimento de queima controlada na Estação Agronômica da UFRGS, em Eldorado do Sul, RS. O design foi em blocos casualizados, com 14 parcelas experimentais de 10 x 10 m pareadas; sendo uma parcela de cada bloco queimada no final da primavera de 2009, e a outra, considerada como controle. Informações sobre invertebrados, processos ecológicos e propriedades abióticas do hábitat foram obtidas em todas parcelas antes do fogo (para a caracterização inicial), e 1 mês, 6-7 meses e 12 meses após o fogo. Para o estudo de caso com aranhas, eu classifiquei as comunidades em famílias, atributos de estratégias de caça e medi todos os indivíduos (1755) em atributos funcionais morfológicos, sendo incorporada toda a variabilidade intra e interespecífica, e fenológica das comunidades. Por outro lado, no estudo de caso com tripes, descrevi atributos funcionais (hábitos alimentares, requerimentos de hábitat e atributos morfológicos) por espécie de tripes (48 spp.), assumindo que a variação nos atributos funcionais é sempre maior entre espécies do que dentro da mesma espécie. Nos dois estudos de caso, eu encontrei padrões indicativos de filtragem ambiental, ou seja, o fogo e/ou as mudanças no hábitat induzidas pelo fogo, parecem ter atuado como um filtro, selecionando organismos com determinado conjunto de atributos em detrimento de outros. Esses padrões foram dependentes do período após a queima considerado, por exemplo: um mês após o fogo aranhas construtoras de teias irregulares e tripes fungívoros foram prejudicados, enquanto que aranhas caçadoras da vegetação, com grandes quelíceras, tripes fitófagos e associados com gramíneas aumentaram suas proporções. Para aranhas ainda verifiquei convergência de atributos ao gradiente de biomassa induzido pelo fogo (filtragem ambiental), e divergência de atributos ao gradiente de heterogeneidade da vegetação, indicativo de limitação de similaridade (i.e. aumento da coexistência de organismos funcionalmente diferentes e diminuição de competição). Finalmente com relação aos processos ecológicos, encontrei correlações interessantes acerca de seus agentes modeladores, e.g. entre a atividade de detritivoria com a decomposição de serapilheira, e desta com a equidade da vegetação em campo não queimado. Também mostro que os processos são sensíveis, mas resilientes, ao distúrbio por fogo, seguindo a recuperação da estrutura de hábitat. Adicionalmente, eu incorporei à tese um capítulo sobre uma técnica para avaliar o processo de detritivoria, denominado bait-lamina test, o qual avalia diretamente as taxas de alimentação de invertebrados detritívoros do solo. Neste estudo pioneiro nos campos do RS, esclareço alguns aspectos metodológicos que possam constituir uma base para futuras pesquisas. Contudo, com esta tese espero estar contribuindo com o conhecimento sobre as respostas das comunidades de invertebrados e dos processos ecológicos ao distúrbio por fogo nos Campos Sulinos. Em geral, posso concluir que a abordagem funcional trouxe muitos benefícios ao monitoramento da biodiversidade, e que há elevada resiliência das assembléias de aranhas e tripes, e dos processos de detritivoria e decomposição às queimadas de pequena escala nos campos. / There is a huge need of monitoring the responses of biodiversity and ecological processes to disturbances and land use changes. Several studies have indicated that the functional approach of biodiversity, based on functional traits, facilitates the understanding of community assembly and ecosystem functionality, and thus assists on the identification of their relationships with environmental factors. In the first chapter of this Thesis I present the functional ecology theory applied to studies on terrestrial invertebrates, and I review what functional traits are, how to use them in community description and monitoring, and why, highlighting the connections between invertebrates and ecological processes. In the following chapters I present experimental studies evaluating the functional responses of two invertebrate groups- spiders (Araneae) and thrips (Thysanoptera) – and ecological processes influenced by invertebrates (detritivory and litter decay) to fire disturbance in Campos grasslands. Burning represents a common strategy for pasture management in Rio Grande do Sul State, and there is a lack of studies regarding their effects on the environment, biodiversity and processes. Our investigation was performed based in a burning experiment at Estação Agronômica of UFRGS, Eldorado do Sul, RS. The design was blocked, with 14 experimental paired plots of 10 x 10 m. One plot from each block was burned at the end of spring 2009, and the other is considered a control plot. Information concerning invertebrates, ecological processes and abiotic habitat proprieties were obtained from all plots before fire (initial characterization) and 1 month, 6-7 months and 12 months after fire. For the spider study case, I classified the organisms in families, feeding strategy traits, and measured all spider individuals (1755) thus incorporating all intra and interspecific variability of the communities. On the other hand, in the thrips study case I described functional traits (feeding habits, habitat requirements, and morphological traits) per species (48 spp.), assuming that the variation on functional traits should be higher between species than within species. In both cases, I found patterns indicating environmental filtering, which means that fire and/or the fire-induced habitat changes acted as a filter, sorting organisms with a determined group of traits instead of others. These patterns were dependent on the period after fire considered. For example, one month after fire irregular web spider builders and fungivorous thrips were more uncommon than expected, while vegetation hunter spiders, with large chelicerae, and leaf feeder thrips and thrips associated to grasses increased their proportions. For spiders we also verified a trait-convergence pattern along the plant biomass gradient induced by fire (environmental filtering), and trait-divergence pattern along the vegetation heterogeneity gradient indicating limiting similarity (i.e. increase in coexistence of functionally different organisms, and reduction of competition). Finally, regarding ecological processes, I found interesting correlations on their drivers, e.g. between detritivory and litter decay, and between these with plant evenness in unburned grasslands. Also, I show that ecological processes are sensitive but resilient to fire, following habitat structure recovery. Additionally, I incorporate to the Thesis a methodology chapter about the bait-lamina test, which evaluates the feeding rates of soil detritivore invertebrates directly. In this pioneer study, I clarify some methodological aspects of measuring invertebrate detritivory that could help future research. Nevertheless, with this Thesis I hope to contribute to the understanding of invertebrate community and ecological processes responses to fire disturbance in South Brazilian grasslands. Overall, I can conclude that a functional approach brings many benefits to biodiversity monitoring, and also that spiders and thrips communities, and detritivory and decomposition processes are very resilient to the change brought by small scale grassland burning.

Made available in DSpace on 2016-06-02T19:31:54Z (GMT). No. of bitstreams: 1 3557.pdf: 232933 bytes, checksum: a68d0a3f658b893e298128c6729a9da2 (MD5) Previous issue date: 2011-03-03 / Universidade Federal de Minas Gerais / Community functioning may be affected by functional diversity, since it measures the extent of complementarity in resource use. We tested whether there was a relationship between functional diversity of woody species and community functioning at fine-scale, using FD as a measure of functional diversity and litter decomposition rate as a surrogate for community functioning. We measured eight functional traits from a woodland cerrado community in southeastern Brazil. We tested the correlation between FD and decomposition rate, between decomposition rate and each trait separately, and between FD and decomposition rate taking into account differences in soil features. There was a non-significant relationship between FD and decomposition rate, even when we considered each trait separately. Decomposition rate was related to aluminium and phosphorus concentration in soil, but not to FD, pointing out that functional diversity was not a good predictor of community functioning. Most studies on the relationships between biodiversity and community functioning at fine scales were carried out by experimental manipulation of diversity and in temperate regions. We carried out this fine scale study as a mensurative experiment and in a tropical savanna. Our findings indicated that the relationship between biodiversity and community functioning is not so straightforward as usually assumed. / O funcionamento das comunidades deve ser afetado pela diversidade funcional, uma vez que mede a extensão da complementaridade no uso de recursos. Testamos se havia relação entre diversidade funcional das espécies arbóreas e o funcionamento da comunidade em escala fina, usando a FD como medida de diversidade funcional e a taxa de decomposição da serapilheira como indicadora do funcionamento. Medimos oito traços funcionais de plantas arbóreas em uma comunidade de cerrado no sudeste do Brasil. Testamos a correlação entre a FD e as taxas de decomposição, entre as taxas de decomposição e cada traço separadamente e entre FD e as taxas de decomposição considerando diferenças nas variáveis edáficas. Não houve relação significativa entre FD e decomposição, mesmo quando consideramos cada traço separadamente. As taxas de decomposição se mostraram relacionadas com as concentrações de alumínio e fósforo e não com a FD. A diversidade funcional não foi uma boa previsora do funcionamento da comunidade. A maioria dos estudos sobre a relação entre diversidade e funcionamento em escalas finas foi desenvolvida por meio da manipulação experimental da diversidade e em regiões temperadas. Nossas descobertas indicaram que a relação entre biodiversidade e funcionamento das comunidades não é tão simples como se assume e contribuem para aprimorar a abordagem atual.

Made available in DSpace on 2016-06-02T19:31:55Z (GMT). No. of bitstreams: 1 3610.pdf: 381494 bytes, checksum: 801cdcfd0eb82f33c299301532707d13 (MD5) Previous issue date: 2011-03-04 / Financiadora de Estudos e Projetos / Assuming that traditional measures of diversity are rough predictors of functioning and that measures that incoporate information about functional traits are better predictors than the traditional ones, functional diversity measures are intensely used nowadays. However, whether the inclusion of functional traits in biodiversity estimation indeed increases our predictive power is rarely tested. Moreover, dendrogram-based functional diversity measures usually do not take abundance into account. By sampling a southern cerrado site in Brazil, we tested whether, when compared to traditional diversity measures, the inclusion of functional traits leads to an increased predictive power in relating functional diversity to community functioning. We demonstrated that it is possible to include abundance in dendrogram-based functional diversity, and tested whether, when compared to functional diversity as usually calculated, the inclusion of abundance leads to an increased predictive power. No diversity measure was related to community functioning, including functional diversity. Nevertheless, we showed that it is possible to include abundance in dendrogram16 based functional diversity measures, even if most indices were correlated with each other. / Assumindo que medidas de diversidade tradicionais são estimativas grosseiras do funcionamento de comunidades e que medidas que incorporam informações dos traços funcionais são melhores do que as tradicionais, medidas de diversidade funcional são bastante utilizadas atualmente. Contudo, raramente é testado se, de fato, a inclusão dos traços funcionais em estimativas de biodiversidade aumenta nosso poder preditivo. Além disso, medidas de diversidade funcional baseadas em dendrogramas geralmente não consideram a abundância. Em uma área de cerrado no sudeste brasileiro, testamos se a inclusão dos traços funcionais leva a um aumento no poder preditivo ao relacionar a diversidade funcional ao funcionamento da comunidade quando comparada a medidas de diversidade tradicionais. Demonstramos que é possível incluir a abundância em medidas de diversidade funcional baseadas em dendrogramas e testamos se a inclusão da abundância eleva o poder preditivo da diversidade funcional em comparação à comumente calculada. Nenhuma medida de diversidade relacionou-se ao funcionamento da comunidade, inclusive a diversidade funcional. Porém, mostramos que é possível incluir a abundância em medidas de diversidade funcional baseadas em dendrogramas, apesar da maioria dos índices estar correlacionada.

Submitted by Katiane Souza (katyane.souza@gmail.com) on 2016-05-12T14:09:26Z No. of bitstreams: 1 arquivototal.pdf: 1764591 bytes, checksum: 8c79fbd17f4301ebf5fb2c42a5a71c72 (MD5) / Made available in DSpace on 2016-05-12T14:09:26Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1764591 bytes, checksum: 8c79fbd17f4301ebf5fb2c42a5a71c72 (MD5) Previous issue date: 2006-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Nutrient cycling is fundamental to forest maintenance, and involves the deposition of organic material, its decomposition and nutrient release for reabsorption by superior plants. These processes are regulated by biotic and abiotic factors that determine the environmental sustainability. This study had the objectives to determine the monthly litter production and the time necessary to the accumulated litter to disappear, characterize the process of decomposition, evaluate the microbial activity and the effect of climatic and soil conditions on it, determine the fluctuations of the microorganisms and mesofauna communities in a Caatinga forest site, and, finally, analyze liter quality in order to identify the different phases of the process of organic matter decomposition and nutrient enrichment. Field work was carried out at the RPPN of the Fazenda Tamanduá, located in Santa Terezinha (PB), from October 2003 to September 2004 (period 1 = P1) and from October 2004 to September 2005 (period 2 = P2) in seven transects systematically located in the RPPN area. Litter production were estimated from monthly litter collection from 20 1mx1m collector boxes randomly distributes in the transects. The collected litter was fractioned into leaves, stems, reproductive structures and miscellany, and then dried and weighed. Every three months the deposited litter on the soil was collected from 0,5mx0,5m frames, dried and weighed, to calculate the decomposition factor (K) and the time required to 50 and 95% of litter decomposition. The rate of litter decomposition was estimated in nylon bags with 30g of dried litter. These 480 nylon bags were divided equitably and placed around the 20 collector boxes. Every month, one nylon bag from each collector bag was recovered from the field and the litter inside was taken out, cleaned and weighed to determine its weight loss. Diurnal and nocturnal microbial activity was measured by means of soil respiration. Macronutrients composition of the deposited litter and in the litter inside the nylon bag was determined. Litter production during P1 and P2 was 1290.9 kg ha-1 and 1947.5 kg ha-1, respectively, totaling 3238.5 kg ha-1. Leaf, stem, reproductive structure and miscellany fractions corresponded to 64.14, 23.48, 10.9 and 1.46% of total litter production, respectively. More litter deposition was observed in the beginning of the dry season. The values of the coefficient of litter decomposition were 1.1 and 1.4 for P1 and P2, respectively, and mean a fast nutrient transfer from litter to soil. The time required to 50 and 95% litter decomposition was 229.9 and 996.4 days, respectively, in P1, and 178.8 and 770.1 days, respectively, in P2. Initial litter weight loss in nylon bags was fast due to the degradation of labile composts by microorganisms, and decreased afterward due to the more resistant and more lignified materials of the remaining litter. Fungi population was larger than the bacteria population, favored by soil water availability. Mesofauna was mainly represented by Diptera’s 67.24% of the total number of counted mesofauna individuals or of the total biomass of mesofauna individuals and Acarine’s (53.49%), in P1 and P2, respectively. The low values of Shannon (0.38) and Pielou (0.15) indexes denoted the distribution heterogeneity of the mesofauna representatives. The order of macronutrient concentrations in the accumulated litter was as follow: N > Ca > S > K > Mg > P. Litter P content was higher than the expected for dry tropical forests. / A ciclagem de nutrientes, fundamental para a manutenção das florestas, envolve desde a deposição de material orgânico, sua decomposição e disponibilidade de nutrientes para os vegetais superiores. Todos esse processos são regulados por fatores bióticos e abióticos que determinam a sustentabilidade do ambiente. Este trabalho teve como objetivos determinar a produção mensal de serapilheira e o tempo necessário para o desaparecimento da serapilheira acumulada; caracterizar o processo de decomposição; avaliar a atividade microbiana e a influência das condições edafoclimáticas durante esse processo; conhecer as flutuações das comunidades de microrganismos e da mesofauna do solo em área de caatinga e, por último, analisar a qualidade da serapilheira a fim de identificar as diferentes fases do processo de decomposição e concentração de nutrientes. O trabalho foi desenvolvido na RPPN pertencente à Fazenda Tamanduá, localizada no município de Santa Terezinha (PB), durante dois anos, sendo o período 1 compreendido de outubro/2003 a setembro/2004 e o período 2 compreendido de outubro/2004 a setembro/2005. Foram demarcados sete transectos, onde foram realizadas todas as avaliações. Para a produção da serapilheira, foram distribuídas 20 caixas coletoras de 1m x 1m, sendo mensalmente coletado todo o material precipitado, que foi separado nas seguintes frações: folhas, galhos, estruturas reprodutivas e miscelânea; depois foi seco em estufa e pesado. A cada três meses foi coletada a serapilheira acumulada no solo, utilizando-se uma moldura metálica de 0,50 m x 0,50 m. Todo o material acumulado na moldura foi retirado, seco em estufa e pesado, calculando-se assim o fator de decomposição K e o tempo necessário para decompor 50% e 95% da serapilheira. Na avaliação da taxa de decomposição da serapilheira, utilizou-se sacola de náilon contendo cada uma 30g de serapilheira previamente seca. Próximo de cada caixa coletora foram distribuídas 24 sacolas de náilon contendo serapilheira, totalizando 480 sacolas. Mensalmente foram coletadas 20 sacolas, sendo o material retirado, limpo e pesado para avaliar a perda de peso em relação ao inicial. Paralelamente, avaliou-se no campo, a atividade microbiana, medida pela respiração edáfica, nos turnos diurno e noturno. Determinou-se também a qualidade química da serapilheira depositada e a que foi decomposta nas sacolas de náilon, quanto à concentração dos macronutrientes. A produção de serapilheira durante o período 1 de estudo foi de 1290,95 kg ha-1 e 1947,56 kg ha-1 no período 2, totalizando 3.238,51 kg ha-1, sendo a fração folhas predominante na serapilheira devolvida ao solo com 64,14%, seguida da fração galhos (23,48%), estruturas reprodutivas (10,92%) e miscelânea (1,46%). A maior deposição ocorreu no início da estação seca, caracterizando a sazonalidade. Os coeficientes de decomposição (K) de 1,1 para o período 1 e, 1,4 para o período 2, indicam uma transferência mais rápida dos nutrientes contidos na serapilheira para o solo. O tempo necessário para decompor 50% e 95% da serapilheira foi de 229,9 dias e 996,4 dias, respectivamente, período 1. No período 2, o tempo de meia vida foi de 178,8 e 770,15 dias para decompor 95%.A maior perda de peso da serapilheira acondicionada nas sacolas de náilon ocorreram no início do período de exposição, resultado da degradação dos compostos lábeis pelos microrganismos, sendo a velocidade do processo diminuída ao longo do tempo, devido a permanência das partes mais resistentes e lignificadas da serapilheira. Quanto a microbiota, a maior população foi de fungos, em relação à de bactérias, estimulado, principalmente, pelas condições favoráveis na disponibilidade hídrica do solo. Os grupos predominantes da mesofauna foram Díptera com 67,24% no período 1 e Acarine com 53,49% no período 2. Os baixos valores nos índices de Shannon (0,38) e de Pielou (0,15), indicaram uma baixa uniformidade na distribuição dos indivíduos. Quanto à composição química da serapilheira, a serapilheira depositada apresentou concentração de nutrientes na seguinte ordem: N > Ca > > S > K > Mg > P, sendo os teores de P encontrados na serapilheira considerados elevados para florestas tropicais secas.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The study was conducted in four distinct classes of soils, namely Yellow Latosol (LAD), Hapludox (RH), Entisol (RQo) and Acrudox typical (LAw), all under savannah vegetation. Four samples were collected per area, in two depths (0-10 and 10-20 cm) and three seasons (summer, winter and spring). An analysis was made on soil chemical and physical and chemical analysis of litter and biochemical. The parameters were: the CO2 flux, microbial respiration, activity of urease and β-glucosidase, the percentage of leaf litter decomposition and total organic carbon (COT). The sites analyzed showed significant differences regarding the chemical properties of soil. The Law soil had the highest CO2 fluxes in times and the minors observed for RQo. No correlation of flow with the concentration of nutrients in the litter. In layer 0 -10 cm, the flow of CO2 was positively correlated with COT, N, K, C / N and C / P. The correlation in the layer 10- 20 cm was positive for the COT and N. The additions of 0.1 and 1% of litter were not sufficient to determine the potential carbon mineralization, only the addition of 10% showed satisfactory results with soil RH presented the largest percentage and was observed for RQo. The major differences in respiration in these soils were observed after the addition of 10% of litter, especially for the RQo. The yield respiratory decreased with increased amount of litter added and the soil had the highest yield for Lad respiratory. The largest differences in yield were observed in the addition of 0.1% of litter. With respect to enzyme activity, the greatest differences were observed in the addition of 10% litter, and soil RQo showed higher activity of the enzyme β-glucosidase and soil RH showed higher activity of the enzyme urease. / O trabalho foi conduzido em quatro classes de solos, a saber: Latossolo Amarelo distrófico (LAd), Latossolo Vermelho distroférrico (LVdf), Neossolo Quartzarênico órtico (RQo) e Latossolo Amarelo ácrico (LAw), todos com vegetação do tipo cerradão. Foram coletadas quatro amostras por área, em duas profundidades (0-10 e 10-20 cm) e em três épocas (verão, inverno e primavera). Foram feitas análises químicas, físicas e bioquímicas para caracterização das amostras de solos e análises químicas da serapilheira. Os parâmetros avaliados foram: fluxo de CO2, respiração microbiana, atividade de urease e β-glicosidase, percentual de decomposição de serapilheira e carbono orgânico total (COT). Os sítios analisados apresentaram diferenças expressivas quanto às propriedades químicas do solo. O solo LAw apresentou os maiores fluxos de CO2 nas épocas e profundidades analisadas e o solo RQo os menores. Não foi observada correlação do fluxo com os teores de nutrientes na serapilheira. Na camada de 0-10 cm, o fluxo de CO2 correlacionou-se positivamente com as variáveis de COT, N, K, C/N e C/P. A correlação na camada de 10-20 cm foi positiva para o COT e N. As adições de 0,1 e 1% de serapilheira não foram suficientes para determinar o potencial de mineralização do carbono. Apenas a adição de 10% mostrou resultados satisfatórios, tendo o solo LVdf apresentado o maior percentual e o RQo o menor. As maiores diferenças quanto a respiração nesses solos foram observadas quando da adição de 10% de serapilheira, com destaque para o solo RQo. O rendimento respiratório decresceu com aumento da quantidade de serapilheira adicionada, sendo que o solo LAd apresentou maior rendimento respiratório. As maiores diferenças no rendimento foram observadas na adição de 0,1% de serapilheira. Com relação a atividade enzimática, as maiores diferenças foram observadas na adição de 10% de serapilheira, sendo que o solo RQo apresentou maior atividade da enzima β-glicosidase e o solo LVdf apresentou maior atividade da enzima urease. / Mestre em Agronomia

Palatability of 20 meadow plant species was assessed in the slug grazing experiment conducted. Monocots exhibited significantly lower palatability than dicots. Litter decomposition rate was assessed in the field litter-bag test. Linear regression analysis was performed to answer the main question whether species palatability is related to litter decomposition rate and whether it is determined by the carbon or nitrogen content. Phylogenetically independent contrasts were used to eliminate correlated phylogeny effect. Regression trees were used to detect the effect of species traits on species palatability and litter decomposition rate.