The effect of forest degradation on ecosystem services related to frugivory and insectivory promoted by birds and mammals in Amazonian forests
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Data
2022-09-08
Autores
Rossi, Liana Chesini [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Florestas tropicais estão enfrentando ameaças impulsionadas por múltiplas atividades antrópicas, como extração seletiva de madeira e fogo. Em toda a Amazônia, as florestas afetadas por essas atividades cobrem cerca de 1 milhão de km2, correspondendo a 17% das florestas remanescentes da região. Dada sua grande extensão, as florestas modificadas pelo homem desempenham um papel importante na conservação das espécies e na prestação de serviços ecossistêmicos. No entanto, distúrbios causados pelo homem afetam negativamente a biodiversidade e os processos ecológicos. Além disso, os impactos destes distúrbios sobre processos ecológicos, como controle da herbivoria e da dispersão de sementes, ainda são pouco compreendidos. Esta tese visa preencher esta lacuna do conhecimento avaliando como os distúrbios causados pelo homem, em particular a extração seletiva de madeira e incêndios florestais afetam comunidades biológicas e processos ecossistêmicos relacionados à regeneração florestal. Em 17 transectos florestais no centro-leste da Amazônia brasileira, usei seis metodologias para registrar 192 espécies frugívoras e 4.670 interações de frugivoria. Além disso, em 30 transectos florestais eu medi a incidência de predação em 4.500 lagartas artificiais. O objetivo do primeiro capítulo foi mensurar os efeitos da extração seletiva de madeira e dos incêndios florestais sobre as comunidades de espécies frugívoras. Os resultados indicam que, florestas queimadas há mais de 15 anos apresentaram baixo número de frugívoros obrigatórios (i.e., ≤80% da dieta baseada em frutas) e de espécies de tamanho corporal grande, ao mesmo tempo que reduziram os valores de diversidade funcional. No segundo capítulo, avaliei os impactos da extração seletiva de madeira e dos incêndios florestais sobre as interações de 8 frugivoria. Descobri que, florestas que queimaram a mais de 15 anos tiveram uma menor diversidade de espécies e interações. Apesar desses efeitos, não encontrei diferenças na estrutura das redes de frugivoria; todas as redes foram altamente modulares e especializadas. Também registrei elevados valores de diversidade beta, resultado da alta dissimilaridade de interação entre as classes florestais. Por fim, no terceiro capítulo, examinei os efeitos dos distúrbios antrópicos sobre a incidência de predação de artrópodes folívoros. Os resultados mostraram uma surpreendente resiliência do processo de controle de artrópodes folívoros à degradação florestal; alta incidência de predação em florestas queimadas durante o El Niño de 2015-16. A incidência de predação em artrópodes folívoros foi realizada principalmente por artrópodes predadores. No geral, esses resultados sugerem que, embora os incêndios florestais recentes não tenham impactado fortemente os processos ecológicos, em longo prazo, incêndios florestais podem levar a mudanças significativas em comunidades ecológicas, reduzindo a ocorrência de frugívoros especialistas e de grande porte, bem como levando à perda da diversidade funcional e de interações de frugivoria na Florestas Amazônica. Portanto, a perda e as mudanças na diversidade taxonômica e funcional devido aos incêndios florestais, somadas as previsões de aumento na frequência desses incêndios, levam à vulnerabilidade dos processos ecológicos, como a frugivoria e da insetivoria –fundamentais para a manutenção e recuperação florestal, com possíveis consequências negativas sobre os serviços ecossistêmicos promovidos pelas florestas tropicais.
Tropical forests are facing threats driven by multiple anthropogenic activities., such as selective logging and fires. Across Amazonia, forests affected by these activities cover c. 1 million km2, corresponding to 17% of remaining forests in the region. Given its large extension, human-modified forests play an important role in species conservation and provision of ecosystem services. However, anthropogenic disturbances negatively affect biodiversity and ecological processes. Furthermore, the impacts of disturbances on ecological processes, such as herbivory control and seed dispersal, are still poorly understood. This thesis aims to fill these knowledge gaps by assessing how human-driven disturbances, in particular selective logging and forest fires, affect biological communities and ecosystems process related to forest regeneration, including insectivory and frugivory. Across 17 forest plots in central-eastern Brazilian Amazon, I combined six methodologies to record 192 frugivorous species; and 4,670 frugivory interactions. Additionally, across 30 plots, I measured predation incidence in 4,500 artificial caterpillars. My first Chapter aim was to measure the effects of selective logging and forest fires on frugivorous communities. The results indicate that forests burned more than 15 years in the past had a distinct frugivorous community composition in comparison to undisturbed forests, limiting the occurrence of obligate (≤80% diet based on fruits) and large-bodied frugivorous, while reduced the values of functional diversity. In the second Chapter, I assessed the impacts of selective logging and forest fires on frugivory interactions. I found that fires that occurred more than 15 years in the past reduced the number of species and unique interactions. Despite these effects, there were no impacts of neither selective logging or forest fires on the 10 structure of frugivory networks - all networks were highly modular and specialized. I also recorded a high beta-diversity of interactions in all forests, resulted from the high interaction dissimilarity among forest classes. Finally, in the third Chapter, I measured the effects of selective logging and forest fires on predation incidence on folivorous arthropods. Results showed a surprising resilience of predation incidence, which were similar between control plots and those affected by selective logging and forest fires. Arthropods were the main predators of caterpillars. Overall, these findings suggest that although fires that occurred <15 years ago have not strongly impacted frugivory and insectivory, fires can lead to significant changes on ecological communities, loss specialist and large frugivorous species as well as diversity of frugivory interactions and functions in Amazonian forests. Therefore, loss and changes in taxonomic and functional diversity due to forest fires, added to predictions of increases in fires frequency, rise up the vulnerability of frugivory and insectivory functions, both fundamental for forest maintenance and recovery, with implication on the services provided by tropical forests.
Tropical forests are facing threats driven by multiple anthropogenic activities., such as selective logging and fires. Across Amazonia, forests affected by these activities cover c. 1 million km2, corresponding to 17% of remaining forests in the region. Given its large extension, human-modified forests play an important role in species conservation and provision of ecosystem services. However, anthropogenic disturbances negatively affect biodiversity and ecological processes. Furthermore, the impacts of disturbances on ecological processes, such as herbivory control and seed dispersal, are still poorly understood. This thesis aims to fill these knowledge gaps by assessing how human-driven disturbances, in particular selective logging and forest fires, affect biological communities and ecosystems process related to forest regeneration, including insectivory and frugivory. Across 17 forest plots in central-eastern Brazilian Amazon, I combined six methodologies to record 192 frugivorous species; and 4,670 frugivory interactions. Additionally, across 30 plots, I measured predation incidence in 4,500 artificial caterpillars. My first Chapter aim was to measure the effects of selective logging and forest fires on frugivorous communities. The results indicate that forests burned more than 15 years in the past had a distinct frugivorous community composition in comparison to undisturbed forests, limiting the occurrence of obligate (≤80% diet based on fruits) and large-bodied frugivorous, while reduced the values of functional diversity. In the second Chapter, I assessed the impacts of selective logging and forest fires on frugivory interactions. I found that fires that occurred more than 15 years in the past reduced the number of species and unique interactions. Despite these effects, there were no impacts of neither selective logging or forest fires on the 10 structure of frugivory networks - all networks were highly modular and specialized. I also recorded a high beta-diversity of interactions in all forests, resulted from the high interaction dissimilarity among forest classes. Finally, in the third Chapter, I measured the effects of selective logging and forest fires on predation incidence on folivorous arthropods. Results showed a surprising resilience of predation incidence, which were similar between control plots and those affected by selective logging and forest fires. Arthropods were the main predators of caterpillars. Overall, these findings suggest that although fires that occurred <15 years ago have not strongly impacted frugivory and insectivory, fires can lead to significant changes on ecological communities, loss specialist and large frugivorous species as well as diversity of frugivory interactions and functions in Amazonian forests. Therefore, loss and changes in taxonomic and functional diversity due to forest fires, added to predictions of increases in fires frequency, rise up the vulnerability of frugivory and insectivory functions, both fundamental for forest maintenance and recovery, with implication on the services provided by tropical forests.
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Ecologia, Funções ecológicas, Distúrbios antrópicos, Florestas tropicais, Interações ecológicas, Incêndios florestais, Anthropogenic disturbances, Ecological functions, Tropical forests, Ecological interactions, Forest fires