Alterações da paisagem de várzea do Baixo Amazonas entre 1970 e 2008

Remote sensing data coupled with landscape ecology metrics were used to investigate the landscape evolution of the Lower Amazon floodplain over ~30 years. 1970 and 2008 vegetation cover maps were used to calculate landscape ecology metrics for forest patches. Results showed a fragmented landscape in both periods, especially at 2008, with increasing forest degradation throughout the study period. The number of forest patches increased, along with a decrease in mean patch size, denotes fragmentation and reduction of forest area in the region. The remaining metrics were also indicative of forest degradation, such as increasing edge area and reduction of core area for forest patches. The clear differences in the amount remaining and its spatial distribution must be considered when planning for biodiversity conservation, as well as information about the fauna, flora and local human populations.Pages: 7778-778

Utilização de imagens ALOS/PALSAR para o mapeamento das áreas periodicamente inundadas do Baixo Amazonas e sua relação com o grau de antropização das várzeas

The purpose of this study is to map the seasonally flooded area of two subareas in the lower Amazon with different degrees of anthropogenic disturbance using ALOS PALSAR images of two different hydrologic periods (3/1/2009 low water, and 7/6/2009 high water). A deforestation map of the last third years was used to select the subareas of high and low anthropogenic disturbance. The following procedures were performed for each subarea: multidate segmentation of ALOS images by region growing method; and unsupervised region classification. Results showed that the seasonally flooded area is larger in the subarea of high anthropogenic disturbance than in the subarea with low disturbance.Pages: 5426-543

Assessment of deforestation in the Lower Amazon floodplain using historical Landsat MSS/TM imagery

The floodplain forests bordering the Amazon River have outstanding ecological, economic, and social importance for the region. However, the original distribution of these forests is not well known, since they have suffered severe degradation since the 16th century. The previously published vegetation map of the Amazon River floodplain (Hess et al., 2003), based on data acquired in 1996, shows enormous difference in vegetation cover classes between the regions upstream and downstream of the city of Manaus. The upper floodplain is mostly covered by forests, while the lower floodplain is predominantly occupied by grasses and shrubs. This study assesses deforestation in the Lower Amazon floodplain over a ~ 30 year period by producing and comparing a historical vegetation map based on MSS/Landsat images acquired in the late 1970s with a recent vegetation map produced from TM/Landsat images obtained in 2008. The maps were generated through the following steps: 1) normalization and mosaicking of images for each decade; 2) application of a linear mixing model transformation to produce vegetation, soil and shade fraction-images; and 3) object-oriented image analysis and classification. For both maps, the following classes were mapped: floodplain forest, non-forest floodplain vegetation, bare soil and open water. The two maps were combined using object-level Boolean operations to identify time transitions among the mapped classes, resulting in a map of the land cover change occurred over ~ 30 years. Ground information collected at 168 ground points was used to build confusion matrices and calculate Kappa indices of agreement. A survey strategy combining field observations and interviews allowed the collection of information about both recent and historical land cover for validation purposes. Kappa values (0.77, 0.75 and 0.75) indicated the good quality of the maps, and the error estimates were used to adjust the estimated deforested area to a value of 3457 km2 ± 1062 km2 (95% CI) of floodplain deforestation over the ~ 30 years

Integração de informações de multi-sensores para estimar alterações da rugosidade hidráulica da várzea do Baixo Amazonas em função da remoção da floresta inundável

This paper describes the integration of floodplain cover types mapped from MSS and TM Landsat images and floodplain topographic data from SRTM to estimate changes in the hydraulic roughness caused by floodplain forest removal in the last forty years. Land cover maps representing each decade (1970 and 2000) were overlaid to a floodplain height map following the concept of high and low varzea proposed by Whittmann et al. (2002, 2004). A look up table of hydraulic roughness coefficient based on published data was then used to compute the hydraulic roughness in both decades and assess the percent change and the impact of deforestation on the hydraulic roughness coefficient. Results showed that the integration of theory on vegetation resistance to flow and different types of remote sensing derived data allowed to estimate the spatial distribution of hydraulic roughness in the lower Amazon floodplain and to compute the loss in hydraulic resistance in a reach stretching from Parintins (AM) to Almeirim (PA).Pages: 5193-520

Estudo da dinâmica de inundação na várzea Amazônica através de termo-sensores de campo

The Amazon floodplain is a complex mosaic of forests, lakes and channels, seasonally inundated by Amazonian rivers. The flood pulse is a key factor in the ecological processes of the várzea, which transforms periodically terrestrial environments into aquatic environments. This dynamics provides habitats for many fauna and flora species and provides a suitable spawning environment and abundant food and habitat for fish larvae protection. JERS-1 radar based mapping estimates that 17% of the Amazon basin is covered by wetlands. However this estimate is based in just one high water in the1996 hydrological year. The launch of ALOS radar based satellite in 2006 with a temporal resolution of 40 days offer a new possibility to better understand the water level annual variation in different habitats. However, these inundation maps derived from satellite images need to be validated with field information. For this it was conducted a field experiment to identify the flooding dates, from 2008 to 2009, in different regions of the floodplain, through the use of temperature sensors (thermosensors or iButtons). Therefore, this paper presents a methodology to detect the flooding period through the use of temperature sensors in the floodplain located in the Mamiraua Sustainable Development Reserve, and also describes the first results of the flooding dynamics of this ecosystem.Pages: 5092-509

Impact of the 2009 extreme water level variation on phytoplankton community structure in Lower Amazon floodplain lakes Impacto da variação extrema do nível da água em 2009 sobre a estrutura da comunidade fitoplanctônica de lagos da planície do Baixo Amazonas

AIM: This paper examines the effect of the extreme water level change in 2009 on the structure and diversity of the phytoplankton communities in lakes of the Lower Amazon Floodplain, and compares it to phytoplankton community structure data reported in the literature for 2002 and 2003 high water periods, closer to the normal hydrological conditions. METHODS: Sub-surface integrated water samples for phytoplankton and chlorophyll-a analyses were collected during high and low water phases in 2009. Water temperature (°C), pH, turbidity (NTU) and electrical conductivity (µS.m-1) were measured, and the Shannon diversity index was calculated. RESULTS: The results showed striking differences in taxonomic composition between phases (high and low) and also between normal (2002 and 2003) and extreme (2009) hydrological conditions, all related to the flood pulse intensity. CONCLUSIONS: Extreme water level fluctuations can result in shifts in phytoplankton community structure and diversity. This work represents a valuable contribution to phytoplankton research since presents the community structure under extreme hydrological events in the Amazon floodplain.OBJETIVO: Esse trabalho investiga o efeito da extrema variação da mudança do nível da água em 2009 na estrutura e diversidade das comunidades de fitoplâncton nos lagos da planície de inundação do Baixo Amazonas,e compara estes resultados à estrutura da comunidade de fitoplâncton reportada na literatura para os períodos de água alta em 2002 e 2003, próximos a condições hidrológicas normais. MÉTODOS: Amostras de água da sub-superfície foram coletadas para a análise de fitoplâncton e clorofila-a nos períodos de água alta e baixa em 2009. Temperatura da água (°C), pH, turbidez (NTU) e condutividade elétrica (µS.m-1) foram medidas, e o índice de diversidade de Shannon calculado. RESULTADOS: Os resultados revelaram diferenças marcantes na composição taxonômica entre fases da inundação (alta e baixa) e também entre eventos hidrológicos normais (2002 e 3003) e extremos (2009), todos relacionados com a intensidade do pulso de inundação. CONCLUSÕES: Flutuações extremas do nível da água podem resultar em alterações na estrutura da comunidade e na diversidade. Esse trabalho é uma contribuição valiosa a pesquisa em fitoplâncton, pois apresenta a estrutura da comunidade sob condições hidrológicas extremas na planície de inundação Amazônica

Mapeamento da antiga cobertura vegetal de várzea do Baixo Amazonas a partir de imagens históricas (1975-1981) do Sensor MSS-Landsat Mapping ancient vegetation cover of the Amazon floodplain using historical MSS/Landsat images (1975-1981)

Este estudo apresenta um mapa da cobertura vegetal da planície de inundação do Rio Amazonas entre as cidades de Parintins (AM) e Almeirim (PA), com base em imagens Landsat-MSS adquiridas entre 1975 e 1981. O processamento digital dessas imagens envolveu a transformação para imagens-fração de vegetação, solo e água escura (sombra), seguido da aplicação de técnicas de segmentação e classificação por região. O mapa resultante da classificação foi organizado em quatro classes de cobertura do solo: floresta de várzea, vegetação não-florestal de várzea, solo exposto e água aberta. A precisão do mapa foi estimada a partir de dois tipos de informações coletadas em campo: 1) pontos de descrição: para validação das classes de cobertura não sujeitas a grandes alterações, como é o caso dos corpos d'água permanentes, e identificação de indicadores dos tipos de cobertura original presentes na paisagem na ocasião da obtenção das imagens (72 pontos); 2) entrevistas com moradores antigos para a recuperação da memória sobre a cobertura vegetal existente há 30 anos (44 questionários). Ao todo foram coletadas informações em 116 pontos distribuídos ao longo da área de estudo. Esses pontos foram utilizados para calcular o Índice Kappa de concordância entre os dados de campo e o mapa resultante da classificação automática, cujo valor (0,78) indica a boa qualidade do mapa de cobertura vegetal da várzea. Os resultados mostram que a região possuía uma cobertura florestal de várzea de aproximadamente 8.650 km2 no período de aquisição das imagens.<br>This study presents a vegetation map of the Amazon River floodplain between the towns of Parintins (AM) and Almeirim (PA), based on Landsat-MSS scenes from 1975 to 1981. Digital processing involved the transformation of multispectral images into fraction-images of vegetation, soil and dark water (shadow), followed by the application of segmentation and region-classification techniques. The resulting map was organized four classes of land cover types: floodplain forest, non-forest floodplain vegetation, bare soil, and open water. Map accuracy was estimated from two types of ground data 1) sample points describing ground cover classes not subjected to major changes, such as permanent water bodies, and identifying indicators of the 30 year old vegetation type landscape (72 points); 2) interviews with community early residents for memory recovery of information on the vegetation cover existing in the 1970 (44 interviews). Altogether, 116 information points was collected along the study area. These points were used to calculate the Kappa Index for agreement between the four field-verified classes and the automatic classification, with value (0.78) indicates the good quality of the floodplain vegetation cover map. The region had 8650 km2 coverage of floodplain forest at the time of image acquisition