A decomposição de serapilheira é um processo fundamental para a ciclagem de nutrientes e a manutenção da fertilidade dos solos em florestas tropicais. Além disso, contribui com os fluxos de carbono para a atmosfera, sendo constantemente discutida no âmbito das mudanças climáticas globais. Dentre os fatores que influenciam na sua dinâmica, o local de origem das espécies vegetais, a qualidade nutricional da serapilheira e a comunidade decompositora do solo tem recebido destaque. Interações entre plantas e decompositores que resultam em uma maior decomposição no local de origem das espécies vegetais em relação a um local externo são denominadas \"home field advantage\" (HFA). O presente estudo teve como objetivos investigar a ocorrência do HFA, bem como a influência das interações entre o local de origem das espécies vegetais, os decompositores do solo e a qualidade nutricional do material vegetal na decomposição de serapilheira em áreas de Floresta Ombrófila Densa Atlântica de terras baixas e montana localizadas no litoral norte do estado de São Paulo. Para isso foi realizado um experimento de decomposição com permuta de material foliar entre as florestas de terras baixas e montana com duração de 250 dias, utilizando folhas senescentes da espécie Rustia formosa, proveniente da floresta de terras baixas, e Licania hoehnei, proveniente da floresta montana, e litter bags com diferentes aberturas de malha para controlar a inclusão exclusão da meso e macro fauna do solo. Também foram quantificadas as concentrações de nutrientes, compostos orgânicos e composição isotópica para determinação da qualidade inicial das serapilheiras e sua dinâmica durante a decomposição. As diferenças na qualidade inicial das espécies não causou diferenciação entre as suas taxas de decomposição. As taxas de decomposição foram semelhantes entre espécies e ambientes, não sendo verificada maior velocidade de decomposição associada com a interação entre as espécies e seus ambientes de origem, o que indica ausência de HFA. Além disso, não foi verificado efeito positivo da fauna do solo na decomposição. A dinâmica química dos detritos foliares evidenciou a imobilização de nitrogênio e acúmulo de lignina ao longo da decomposição, o que indica limitação na atividade microbiana por nitrogênio e baixa qualidade da serapilheira de Rustia formosa e Licania hoehnei. As variações nas concentrações de carbono, nitrogênio e fósforo influenciaram a dinâmica da decomposição ao longo do tempo. Esse estudo contribui para compreensão de como fatores importantes na decomposição interagem em ecossistemas tropicais, e aponta a importância da qualidade da serapilheira e disponibilidade de nutrientes no ambiente como direcionadores da decomposição. / Litter decomposition is a key process for nutrient cycling and maintenance of soil fertility in tropical forests, contributing to carbon fluxes to the atmosphere and being constantly discussed in the global climate change scenario. Among the main factors that control decomposition, the place of origin of species, litter quality and soil community are currently with great attention. Interactions between plants and decomposers that lead to a fast decomposition in the place of origin of species related to other sites and species are called home field advantage (HFA). The goal of this study was to investigate the occurrence of HFA, as well the influence of interactions between place of origin, soil decomposers and litter quality on the litter decomposition in areas of lowland and montane Atlantic forest located in the north coast of Sao Paulo state. For this it was performed an decomposition experiment with transplant of litter of Rustia Formosa, from lowland forest, and Licania hoehnei, from montane forest, between the two forests, with duration of 250 days, using litter bags with different mesh sizes to allow and exclude the access of meso and macro soil fauna. It was also quantified nutrient and organic compounds concentration to determine the initial litter quality and its dynamics during decomposition. The differences in initial litter quality between species did not cause differentiation in the decomposition rate. The decomposition rates were similar between species and ambient, with no faster decomposition associated with the interaction between species and its local places of origin, which indicates lack of HFA. Besides that, there was no positive effect of soil fauna on the decomposition. The chemical dynamics of litter pointed out nitrogen immobilization and lignin accumulation during decomposition, which indicates microbial limitation by nitrogen and low litter quality of Rustia Formosa and Licania hoehnei. The variations in carbon, nitrogen and lignin concentration influenced the dynamics of decomposition during the time. This study contributed to the comprehension of how important factors of decomposition can interact in tropical ecosystems, and pointed the importance of litter quality and nutrient availability of the ambient as drivers of decomposition.

A decomposição de serapilheira é um processo fundamental para a ciclagem de nutrientes e a manutenção da fertilidade dos solos em florestas tropicais. Além disso, contribui com os fluxos de carbono para a atmosfera, sendo constantemente discutida no âmbito das mudanças climáticas globais. Dentre os fatores que influenciam na sua dinâmica, o local de origem das espécies vegetais, a qualidade nutricional da serapilheira e a comunidade decompositora do solo tem recebido destaque. Interações entre plantas e decompositores que resultam em uma maior decomposição no local de origem das espécies vegetais em relação a um local externo são denominadas \"home field advantage\" (HFA). O presente estudo teve como objetivos investigar a ocorrência do HFA, bem como a influência das interações entre o local de origem das espécies vegetais, os decompositores do solo e a qualidade nutricional do material vegetal na decomposição de serapilheira em áreas de Floresta Ombrófila Densa Atlântica de terras baixas e montana localizadas no litoral norte do estado de São Paulo. Para isso foi realizado um experimento de decomposição com permuta de material foliar entre as florestas de terras baixas e montana com duração de 250 dias, utilizando folhas senescentes da espécie Rustia formosa, proveniente da floresta de terras baixas, e Licania hoehnei, proveniente da floresta montana, e litter bags com diferentes aberturas de malha para controlar a inclusão exclusão da meso e macro fauna do solo. Também foram quantificadas as concentrações de nutrientes, compostos orgânicos e composição isotópica para determinação da qualidade inicial das serapilheiras e sua dinâmica durante a decomposição. As diferenças na qualidade inicial das espécies não causou diferenciação entre as suas taxas de decomposição. As taxas de decomposição foram semelhantes entre espécies e ambientes, não sendo verificada maior velocidade de decomposição associada com a interação entre as espécies e seus ambientes de origem, o que indica ausência de HFA. Além disso, não foi verificado efeito positivo da fauna do solo na decomposição. A dinâmica química dos detritos foliares evidenciou a imobilização de nitrogênio e acúmulo de lignina ao longo da decomposição, o que indica limitação na atividade microbiana por nitrogênio e baixa qualidade da serapilheira de Rustia formosa e Licania hoehnei. As variações nas concentrações de carbono, nitrogênio e fósforo influenciaram a dinâmica da decomposição ao longo do tempo. Esse estudo contribui para compreensão de como fatores importantes na decomposição interagem em ecossistemas tropicais, e aponta a importância da qualidade da serapilheira e disponibilidade de nutrientes no ambiente como direcionadores da decomposição. / Litter decomposition is a key process for nutrient cycling and maintenance of soil fertility in tropical forests, contributing to carbon fluxes to the atmosphere and being constantly discussed in the global climate change scenario. Among the main factors that control decomposition, the place of origin of species, litter quality and soil community are currently with great attention. Interactions between plants and decomposers that lead to a fast decomposition in the place of origin of species related to other sites and species are called home field advantage (HFA). The goal of this study was to investigate the occurrence of HFA, as well the influence of interactions between place of origin, soil decomposers and litter quality on the litter decomposition in areas of lowland and montane Atlantic forest located in the north coast of Sao Paulo state. For this it was performed an decomposition experiment with transplant of litter of Rustia Formosa, from lowland forest, and Licania hoehnei, from montane forest, between the two forests, with duration of 250 days, using litter bags with different mesh sizes to allow and exclude the access of meso and macro soil fauna. It was also quantified nutrient and organic compounds concentration to determine the initial litter quality and its dynamics during decomposition. The differences in initial litter quality between species did not cause differentiation in the decomposition rate. The decomposition rates were similar between species and ambient, with no faster decomposition associated with the interaction between species and its local places of origin, which indicates lack of HFA. Besides that, there was no positive effect of soil fauna on the decomposition. The chemical dynamics of litter pointed out nitrogen immobilization and lignin accumulation during decomposition, which indicates microbial limitation by nitrogen and low litter quality of Rustia Formosa and Licania hoehnei. The variations in carbon, nitrogen and lignin concentration influenced the dynamics of decomposition during the time. This study contributed to the comprehension of how important factors of decomposition can interact in tropical ecosystems, and pointed the importance of litter quality and nutrient availability of the ambient as drivers of decomposition.

Résumé : La décomposition des litières végétales a été décrite comme étant la deuxième plus importante fonction écosystémique sur terre, après la productivité primaire. Alors que la photosynthèse fournit les apports énergétiques à la plupart des chaînes alimentaires, la décomposition recycle les nutriments, permet leur utilisation future par d’autres organismes et relargue dans l’atmosphère le carbone fixé photosynthétiquement. Dans un contexte de changement climatique, un grand intérêt est porté sur la décomposition des litières, car il s’agit, à l’échelle globale, de la plus grande source d’émission de CO[indice inférieur 2] dans l’atmosphère. Les taux de décomposition des litières sont principalement déterminés par trois facteurs: les variables climatiques, la structure des communautés de décomposeurs et les propriétés chimiques et physiques de la litière. La structure de la communauté végétale hôte dans laquelle se produit la décomposition et d’où provient la litière peut influencer l’ensemble de ces trois facteurs. Des changements dans la structure de la communauté végétale pourraient donc affecter les futurs taux de décomposition et modifier significativement les dynamiques globales du carbone. Malgré cela, la communauté hôte est rarement prise en compte dans les études sur la décomposition des litières. Des expériences enlèvent souvent la litière de son environnment naturel de décomposition, mesurant la décomposition des litières à partir de monolithes ou de microcosmes en laboratoire, afin de contrôler les variations indésirables des propriétés du sol. Dans ce mémoire, j’étudie les effets de plusieurs propriétés fonctionnelles de la communauté végétale hôte sur les taux de décomposition des litières et leur contribution à la respiration du sol. En utilisant une plantation expérimentale d’arbres qui permet de manipuler la structure de leur communauté, je teste l’effet de l’identité fonctionnelle des arbres, des espèces et de la diversité fonctionnelle, ainsi que des interactions entre décomposeurs et arbres sur ces processus écosystémiques. La décomposition des litières et la respiration du sol sont liées aux propriétés fonctionnelles des plantes. La décomposition des litières est bien prédite par les valeurs moyennes de traits fonctionnels des litières, mais plus faiblement corrélée à la diversité spécifique. D’après mes résultats, le nombre d’espèces en mélange de litières ne constitue pas un facteur important pour la décomposition, à cause des interactions globalement idiosyncratiques entre types de litières. Cependant, l’augmentation conjointe de la diversité fonctionnelle des mélanges d’espèces en litières et de la communauté d’arbres-hôtes accélère les taux de décomposition et la respiration du sol. Les premières phases de décomposition de litières en surface ne sont que faiblement affectées par la diversité des plantes, alors que pour la respiration du sol, qui prend en compte les dernières phases de décomposition de litière et de matière organique du sol, la diversité est la propriété fonctionnelle de plantes qui fournit le meilleur pouvoir de prédiction. De plus, j’ai trouvé que les apports spécifiques de litières à long terme pouvaient créer des conditions qui favorisent la décomposition des litières native et pouvaient modifier l’effet de la diversité des arbres sur la décomposition. J’attribue cet effet aux rétroactions entre la litière et les organismes décomposeurs du sol. Ce travail de recherche fournit une nouvelle perspective sur les effets des changements de structure de communauté forestière sur les processus de décomposition. La compréhension de ces effets est nécessaire pour prédire les taux de décomposition de litières et les dynamiques globales du carbone. // Abstract : The decomposition of plant litter has been described as the second most important ecosystem function for sustaining life on earth, after primary productivity. Whereas photosynthesis provides the energy input for most food chains, decomposition recycles nutrients for future use by other organisms and returns photosynthetically fixed carbon back to the atmosphere. In the context of climate change, litter decomposition is of specific interest because it represents one of the largest sources of CO[subscript 2] to the atmosphere globally. Rates of litter decomposition are largely determined by three factors: climatic variables, the structure of the decomposer community, and the chemical and physical properties of the litter. The structure of the host plant community under which decomposition takes place and from which the litter is derived can influence all three of these factors. Therefore, any systematic changes in plant community structure could affect future decomposition rates and significantly alter global carbon dynamics. Despite this, the host plant community is rarely considered in litter decomposition studies. Experiments often remove litter from its natural decomposition environment, instead measuring decomposition of litter in common garden settings and laboratory microcosms to control for unwanted variation in soil properties. In this thesis I investigate the effect of several functional properties of the host plant community on rates of litter decomposition and its contribution to soil respiration. Using an experimental tree plantation that manipulates tree community structure, I test the effect of tree functional identity, species and functional diversity, and tree-decomposer interactions on these ecosystem processes. Both litter decomposition and soil respiration were related to plant functional properties. Litter decomposition was best predicted by average-values of litter functional traits and was poorly related to species diversity. The number of species in a litter mixture does not seem to be important for decomposition, as interactions between litter types were idiosyncratic. However increasing the functional diversity both of mixed-species litter and of the host tree community accelerated rates of litter decomposition and soil respiration. Early stages of surface litter decomposition were only marginally affected by plant diversity. In contrast, diversity was the best predictor of soil respiration, which includes latter stages of litter and soil organic matter decomposition. Furthermore, I found that specific repeated litter input to the soil can result in conditions that favour the decomposition of the long-term litter type and can mediate the effect of tree diversity on decomposition. I attribute this effect to feedbacks between the litter and soil decomposer organisms. This research provides insight into the effect of changing forest community structure on decomposition processes. Such an understanding is necessary to predict future rates of litter decomposition and global carbon dynamics.

R??sum?? : La d??composition des liti??res v??g??tales a ??t?? d??crite comme ??tant la deuxi??me plus importante fonction ??cosyst??mique sur terre, apr??s la productivit?? primaire. Alors que la photosynth??se fournit les apports ??nerg??tiques ?? la plupart des cha??nes alimentaires, la d??composition recycle les nutriments, permet leur utilisation future par d???autres organismes et relargue dans l???atmosph??re le carbone fix?? photosynth??tiquement. Dans un contexte de changement climatique, un grand int??r??t est port?? sur la d??composition des liti??res, car il s???agit, ?? l?????chelle globale, de la plus grande source d?????mission de CO[indice inf??rieur 2] dans l???atmosph??re. Les taux de d??composition des liti??res sont principalement d??termin??s par trois facteurs: les variables climatiques, la structure des communaut??s de d??composeurs et les propri??t??s chimiques et physiques de la liti??re. La structure de la communaut?? v??g??tale h??te dans laquelle se produit la d??composition et d???o?? provient la liti??re peut influencer l???ensemble de ces trois facteurs. Des changements dans la structure de la communaut?? v??g??tale pourraient donc affecter les futurs taux de d??composition et modifier significativement les dynamiques globales du carbone. Malgr?? cela, la communaut?? h??te est rarement prise en compte dans les ??tudes sur la d??composition des liti??res. Des exp??riences enl??vent souvent la liti??re de son environnment naturel de d??composition, mesurant la d??composition des liti??res ?? partir de monolithes ou de microcosmes en laboratoire, afin de contr??ler les variations ind??sirables des propri??t??s du sol. Dans ce m??moire, j?????tudie les effets de plusieurs propri??t??s fonctionnelles de la communaut?? v??g??tale h??te sur les taux de d??composition des liti??res et leur contribution ?? la respiration du sol. En utilisant une plantation exp??rimentale d???arbres qui permet de manipuler la structure de leur communaut??, je teste l???effet de l???identit?? fonctionnelle des arbres, des esp??ces et de la diversit?? fonctionnelle, ainsi que des interactions entre d??composeurs et arbres sur ces processus ??cosyst??miques. La d??composition des liti??res et la respiration du sol sont li??es aux propri??t??s fonctionnelles des plantes. La d??composition des liti??res est bien pr??dite par les valeurs moyennes de traits fonctionnels des liti??res, mais plus faiblement corr??l??e ?? la diversit?? sp??cifique. D???apr??s mes r??sultats, le nombre d???esp??ces en m??lange de liti??res ne constitue pas un facteur important pour la d??composition, ?? cause des interactions globalement idiosyncratiques entre types de liti??res. Cependant, l???augmentation conjointe de la diversit?? fonctionnelle des m??langes d???esp??ces en liti??res et de la communaut?? d???arbres-h??tes acc??l??re les taux de d??composition et la respiration du sol. Les premi??res phases de d??composition de liti??res en surface ne sont que faiblement affect??es par la diversit?? des plantes, alors que pour la respiration du sol, qui prend en compte les derni??res phases de d??composition de liti??re et de mati??re organique du sol, la diversit?? est la propri??t?? fonctionnelle de plantes qui fournit le meilleur pouvoir de pr??diction. De plus, j???ai trouv?? que les apports sp??cifiques de liti??res ?? long terme pouvaient cr??er des conditions qui favorisent la d??composition des liti??res native et pouvaient modifier l???effet de la diversit?? des arbres sur la d??composition. J???attribue cet effet aux r??troactions entre la liti??re et les organismes d??composeurs du sol. Ce travail de recherche fournit une nouvelle perspective sur les effets des changements de structure de communaut?? foresti??re sur les processus de d??composition. La compr??hension de ces effets est n??cessaire pour pr??dire les taux de d??composition de liti??res et les dynamiques globales du carbone. // Abstract : The decomposition of plant litter has been described as the second most important ecosystem function for sustaining life on earth, after primary productivity. Whereas photosynthesis provides the energy input for most food chains, decomposition recycles nutrients for future use by other organisms and returns photosynthetically fixed carbon back to the atmosphere. In the context of climate change, litter decomposition is of specific interest because it represents one of the largest sources of CO[subscript 2] to the atmosphere globally. Rates of litter decomposition are largely determined by three factors: climatic variables, the structure of the decomposer community, and the chemical and physical properties of the litter. The structure of the host plant community under which decomposition takes place and from which the litter is derived can influence all three of these factors. Therefore, any systematic changes in plant community structure could affect future decomposition rates and significantly alter global carbon dynamics. Despite this, the host plant community is rarely considered in litter decomposition studies. Experiments often remove litter from its natural decomposition environment, instead measuring decomposition of litter in common garden settings and laboratory microcosms to control for unwanted variation in soil properties. In this thesis I investigate the effect of several functional properties of the host plant community on rates of litter decomposition and its contribution to soil respiration. Using an experimental tree plantation that manipulates tree community structure, I test the effect of tree functional identity, species and functional diversity, and tree-decomposer interactions on these ecosystem processes. Both litter decomposition and soil respiration were related to plant functional properties. Litter decomposition was best predicted by average-values of litter functional traits and was poorly related to species diversity. The number of species in a litter mixture does not seem to be important for decomposition, as interactions between litter types were idiosyncratic. However increasing the functional diversity both of mixed-species litter and of the host tree community accelerated rates of litter decomposition and soil respiration. Early stages of surface litter decomposition were only marginally affected by plant diversity. In contrast, diversity was the best predictor of soil respiration, which includes latter stages of litter and soil organic matter decomposition. Furthermore, I found that specific repeated litter input to the soil can result in conditions that favour the decomposition of the long-term litter type and can mediate the effect of tree diversity on decomposition. I attribute this effect to feedbacks between the litter and soil decomposer organisms. This research provides insight into the effect of changing forest community structure on decomposition processes. Such an understanding is necessary to predict future rates of litter decomposition and global carbon dynamics.