Ecologia, etnoecologia e uso local de matupás na Reserva de Desenvolvimento Sustentável Amanã, Amazônia Central

Abstract

Ecological research and ethnoecological investigation have strong potential to allow us to better know and understand ecological processes, by using different methods and approaches. They can be complementary and studies that seek to connect them tend to result in more complete and informative labors. In this study, traditional and scientific knowledge were used together to obtain information about matupás, floating islands that occur in Amazonian floodplain lakes. Matupás are formed by a block of partially decomposed organic material at its base and a plant and animal community on its surface. By having an organic substrate with characteristics of peat matupás can be also considered as peatlands. Although there are many studies about the different types of floating islands and peatlands around the world, there is little information within the Amazon. Scientific knowledge about matupás is still incipient, there are actually no studies focusing solely on these islands. On the other hand, riverine people who live near matupás show profound knowledge about these islands and use them in activities related to agriculture and fishery. In this study, we gathered information from a floristic inventory (herbaceous/woody plants) in matupás located in the Amanã Sustainable Development Reservation (Amazonas, Brazil) and from interviews with riverine people living in the Reservation. Therefore, we (i) sampled 10 matupás establishing plots of 5 x 5 m for sampling woody species and substrate thickness and subplots of 1 x 1 m for sampling herbaceous species (n = 82 plots and subplots), and we also (ii) conducted 35 interviews in five riverine communities, getting information about the matupás formation process; biotic and abiotic factors related to their occurrence, their ecological importance and its usefulness to riverine people. According to data obtained from the inventory we conclude that substrate thickness is an important parameter for the plants occurrence and distribution in matupás. As the thickness increases, the number of woody species also increases and a species replacement occurs, changing matupá physiognomy. Matupás thicker also exhibit greater floristic dissimilarity between its sites, which indicates that they are more heterogeneous environments. From the interviews, we obtained detailed explanations of processes related to matupás, with points of high ecological relevance that were still unknown to science. Among them are the importance of seasonal dynamics of water level fluctuations for matupá formation and the relevance of these islands to the abundance of large fish in the lakes. Floristic composition data provided by the interviewed were compared to results of our inventory in matupás, showing relationships between them. For locals, matupás are an important source of fertilizer in cultivation and a good place to fish pirarucu (Arapaima gigas), and have indirect importance by favoring the greater abundance of fish in the lakes.