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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior As pesquisas científicas têm se intensificado na tentativa de entender as causas e conseqüências das alterações drásticas causadas pelas empreitadas humanas nas florestas primárias (florestas que nunca foram desmatadas), e o papel de florestas secundárias na retenção de diversidade e oferta de serviços ambientais. Uma questão fundamental tem sido avaliar se alterações na biodiversidade (principalmente composição e riqueza de espécies) são capazes de afetar a intensidade e estabilidade dos processos ecossistêmicos. Neste trabalho, foi analisado o papel da diversidade arbórea em florestas secundárias, primárias e em fragmentos florestais para a retenção de carbono na região da mata nordestina, e também analisada a viabilidade da estimação remota de carbono através de índices espectrais de vegetação calculados de satélites. Foi encontrado que a riqueza do grupo tolerantes a sombra é o componente da diversidade mais importante em florestas primárias e secundárias para explicar a retenção de carbono. Também foi verificado que o grupo das árvores emergentes é o mais importante na retenção de carbono em florestas primárias, e sua perda nos fragmentos causa um queda acentuada na retenção de carbono. Por último, não foi possível uma estimação precisa do carbono florestal através de índices espectrais, mas os resultados encontrados indicam que a abordagem é promissora. A presente dissertação confirma a importância da diversidade como fator determinante para o funcionamento dos ecossistemas

Community trait assembly in highly diverse tropical rainforests is still poorly understood. Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (the Lund-Potsdam-Jena General Ecosystem Simulator, LPJ-GUESS) to explore the main drivers of community assembly along an elevational gradient. - In the model used here (LPJ-GUESS-NTD, where NTD stands for nutrient-trait dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake. - The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient-use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced net primary production (NPP) by 61–72% along the gradient. - Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions.

Understanding the processes that shape forest functioning, structure, and diversity remains challenging, although data on forest systems are being collected at a rapid pace and across scales. Forest models have a long history in bridging data with ecological knowledge and can simulate forest dynamics over spatio‐temporal scales unreachable by most empirical investigations. We describe the development that different forest modelling communities have followed to underpin the leverage that simulation models offer for advancing our understanding of forest ecosystems. Using three widely applied but contrasting approaches – species distribution models, individual‐based forest models, and dynamic global vegetation models – as examples, we show how scientific and technical advances have led models to transgress their initial objectives and limitations. We provide an overview of recent model applications on current important ecological topics and pinpoint ten key questions that could, and should, be tackled with forest models in the next decade. Synthesis. This overview shows that forest models, due to their complementarity and mutual enrichment, represent an invaluable toolkit to address a wide range of fundamental and applied ecological questions, hence fostering a deeper understanding of forest dynamics in the context of global change., Ecology and Evolution, 11 (9), ISSN:2045-7758