Navegando por Assunto "Floresta amazônica"

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Acesso aberto (Open Access)
Carbon content in Amazonian Oxisols after forest conversion to pasture
(2009-12) SILVA JÚNIOR, Mário Lopes da; DESJARDINS, Thierry; SARRAZIN, Max; MELO, Vânia Silva de; MARTINS, Paulo Fernando da Silva; SANTOS, Elaine Rodrigues; CARVALHO, Claudio Jose Reis de
Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated land affects C dynamic and stock. This study was developed in an area of expansion of human settlement in the Eastern Amazon, in Itupiranga, State of Pará, to evaluate the effects of native forest conversion to Brachiaria brizantha pasture on C contents of a dystrophic Oxisol. Soil samples were collected in areas of native forest (NF), of 8 to 10 year old secondary forest (SF), 1 to 2 year old SF (P1–2), 5 to 7 year old SF (P5–7), and of 10 to 12 year old SF (P10–12), and from under pastures, in the layers 0–2, 2–5 and 5–10 cm, to evaluate C levels and stocks and carry out separation of OM based on particle size. After deforestation, soil density increased to a depth of 5 cm, with greater increase in older pastures. Variation in C levels was greatest in the top soil layer; C contents increased with increasing pasture age. In the layers 2–5 and 5–10 cm, C content proved to be stable for the types of plant cover evaluated. Highest C concentrations were found in the silt fraction; however, C contents were highest in the clay fraction, independent of the plant cover. An increase in C associated with the sand fraction in the form of little decomposed organic residues was observed in pastures, confirming greater sensitivity of this fraction to change in soil use.
Acesso aberto (Open Access)
Drosophilidae (Insecta, Diptera) como indicador de degradação florestal na área de endemismo Belém, Amazônia Oriental
(Universidade Federal do Pará, 2016-03-31) FERREIRA, Annícia Barata Silva Maciel; MARTINS, Marlúcia Bonifácio; http://lattes.cnpq.br/8882047165338427
Forest degradation results is a major threat to the biodiversity of the Amazon. One of the consequence of degradation is to facilitate colonization by exotic species. This study tested exotic species of frugivorous Drosophilidae as indicators of forest degradation in eight forest remnants in the Belém Endemic Center in northern Brazil. The percentages of primary forest within 10 km and within 100 m of the collection site, as well as eight vegetation structural variables (tree density, basal tree area, understorey density, canopy cover, vine density and intensity, average diameter of trees (dbh>10 cm), and Cecropia spp. density) were analyzed to define a gradient of forest degradation. A total of 5278 fruit flies of 33 species were collected in traps baited with fermented bananas, of which 2803 were exotics, mostly D. malerkotliana. Vegetation structure was more important than landscape structure on the fruit fly guild. More disturbed areas, as shown by vegetation analysis, had a greater number of exotic species, while less disturbed areas had mostly neotropical species. Nine indicator species of degraded, partially degraded, and undisturbed forests were selected based on their Individual Indicator Values (IndVal). These are: Drosophila melanogaster, Zaprionus indianus and Scaptodrosophila latifasciaeformes for degraded sites; D. subsaltans and D. camargoi for well conserved sites; and D. fumipennis, and morpho-species AC10001 for partially degraded sites. Both the list of observed species and the number of fruit fly species can indicate the degree of forest degradation. The guild of frugivorous Drosophilidae can be an important tool in forest conservation and in understanding the effect of anthropogenic interventions on forest environments. An addition advantage to use the contrast between exotic and native species is the taxonomic identification, exotic fruit flies are readily recognizable and distinct from native species. Moreover, these organisms are sensitive to slight environmental alterations and should permit the detection of changes in the initial stages of invasion by exotic species, thus giving an early warning of impacts to the forest biota.
Acesso aberto (Open Access)
Environmental changes during the last millennium based on multi-proxy palaeoecological records in a savanna-forest mosaic from the northernmost Brazilian Amazon region
(Universidade Federal do Pará, 2015-09) MENESES, Maria Ecilene Nunes da Silva; COSTA, Marcondes Lima da; ENTERS, Dirk; BEHLING, Hermann
The environmental changes and the dynamics of the savanna-forest mosaic, over the last 1050 years, have been reconstructed by pollen, charcoal, radiocarbon dating mineralogical and geochemical analyses of sediment cores taken from three different Mauritia flexuosapalm swamps in the northernmost part of the Brazilian Amazon region (northern state of Roraima). Studies on the relationship between the modern pollen rain and the regional vegetation provide additional information for the interpretation of the fossil pollen records. The fossil pollen assemblages and geochemical results indicate relatively wet climatic conditions throughout the recorded period. Despite these moist conditions, fires were frequent and are one of the reasons for the dominance of a grassy savanna instead of forest expansion in the study area. Considering the generally wet climatic conditions, these fires were most likely caused by human activities. Even today, fires hinder forest expansion into savanna areas. Sandy hydromorphic soils may also act as an edaphic control to maintain the current sharp boundary between forest and savanna ecosystems.
Acesso aberto (Open Access)
Fixação biológica de nitrogênio em florestas secundárias e florestas primárias queimadas na Amazônia Centro-Oriental
(Universidade Federal do Pará, 2018-02-28) NASCIMENTO, Rodrigo Oliveira do; BARLOW, Jos; FERREIRA, Joice Nunes; http://lattes.cnpq.br/1679725851734904
Understanding the mechanisms that influence the regeneration capacity of tropical forests is highly relevant in the current context of great loss and degradation of ecosystems. Species of Fabaceae family present resilience after disturbances through the symbiotic mechanism of Biological Nitrogen Fixation (BNF), important for the maintenance of biogeochemical cycles of the ecosystems. The aim of this work was to investigate the role of biological nitrogen fixation in the natural regeneration of secondary forests and burned primary forests in the eastern-central Amazon region. For this, 15 transects (0,25ha each one) were studied, covering three forest classes: secondary forests (> 17.5 years), recently burned primary forests (17 months) and undisturbed primary forests. All individuals of the Fabaceae family (DAP> 10cm) with nodulation potential indicated in the literature occurring in the transects were selected and evaluated. Soil samples were collected to check the presence of active nodules, and nodulation was estimated at individual, species, forest class and ecosystem levels. The total carbon and nitrogen in the soil were evaluated. A GLM model was used to test the main predictor variables that explain the nodular mass increment, including carbon and nitrogen content in soils and dendometric variables (diameter at breast height, canopy area and root mass). Of the 133 individuals studied, 43 (32%) were detected with active nodules. This represented 18 species and 9 genera of Fabaceae family. The genus Inga presented the highest nodulation frequency, with the species Inga pilosula showing the largest nodule mass (6,14 g.m-2). A large intraspecific variation of nodular mass was found in the study. Secondary forests showed a probability of nodulation three to fivefold higher than the other forest classes. Moreover, the total nodule mass was higher in secondary forests (9.37 g.m2) in comparison to burned forests (6.54 g.m2) and undisturbed forests (3.05 g.m2). No strong evidences were found for an important contribution of the biological fixation of nitrogen in burned forests. The main explanatory variable for nodule mass was soil total carbon. Along with carbon, other variables were also selected as predictors of nodule mass: soil total nitrogen, diameter at breast height (DBH) and canopy area. The results suggested an important contribution of biological nitrogen fixation in the regeneration of forests in the Santarém region, mainly in secondary forests and the potential of nitrogen inputs into the ecosystem through biological fixation. The results of the present study are important to increase the understanding of the mechanisms that drive the Amazon forest recovery to disturbances.
Acesso aberto (Open Access)
Influência de variáveis meteorológicas na produção de liteira na Estação Científica Ferreira Penna, Caxiuanã, Pará
(Instituto Nacional de Pesquisas da Amazônia, 2009-09) SILVA, Rosecélia Moreira da; COSTA, José Maria Nogueira da; RUIVO, Maria de Lourdes Pinheiro; COSTA, Antonio Carlos Lôla da; ALMEIDA, Samuel Soares
The evaluation of the influence on the exclusion of rainfall on the variation of litter production was done in Caxiuanã Forest Reserve at Ferreira Penna Scientific Station (1º 42 ' S, 51º 31 ' W) during the period from March, 2001 to February, 2003 with the objective of identifying the main meteorological variables and the main components of the monthly water balance that affected the production and decomposition of litter. This work was part of the subproject EXPERIMENT OF DROUGHT IN THE FOREST (ESECAFLOR), that aimed to study the long term impacts of drought on the water, energy and carbon dioxide fluxes in the Amazon forest. The sazonality of total litter production and its components (leaves, brushwood and reproductive parts) was well established, with the occurrence of a greater litter production during the months with lower precipitation. The monthly litter production during the experimental period ranged from 294.78 kg.ha-1 to 1758.69 kg.ha-1, with an average of 777.70 kg.ha-1. The total litter production was partitioned in leaves (61.40 %), brushwoods (18.45 %) and reproductive parts (20.14 %). The results obtained in the undisturbed plot showed a higher litter production, about 25 %, compared to the litter production in the plot under the exclusion of water. The variables more strongly correlated with litter production and its components were wind speed, global solar radiation density flux, photosynthetic active radiation density flux, soil temperature at 5 cm depth, precipitation, soil water deficit and water surplus.
Acesso aberto (Open Access)
Modelagem ambiental na floresta nacional do Jamanxim-PA: proposta de cenário futuro
(Universidade Federal do Pará, 2022-02-21) GAMA, Luana Helena Oliveira Monteiro; ALMEIDA, Arlete Silva de; http://lattes.cnpq.br/1511094180664778
Protected areas were created essentially for the conservation of fauna and flora. Analyzing its socio-environmental dynamics becomes a challenge, and at the same time contributes to the understanding of the landscape. The present study aims to model future scenarios from remote sensing and geoprocessing techniques in the National Forest (FLONA) of Jamanxim-PA, based on the land use classification of the years 2013 and 2020. Analyze the independent variables through of Artificial Intelligence. Apply the DINAMICA EGO model using the transition method to simulate deforestation trajectories up to 2030, based on the dependent variables (land cover and use 2013 and 2020) and independent variables (altimetry, slope, distance to roads, distance to settlements and distance to hydrography. The high rates of deforestation within the limits of conservation units, lead to large environmental losses over time. According to INPE, the state of Pará presented the highest forest loss of the Brazilian Amazon states in 2019, a total of 3,862 km2 , with an increase rate of 41% when compared to 2018. Through the mathematical model it is possible to analyze “Where” will be deforested; “When” will it be deforested and what deforestation rates will be; and “How”, what will be the spatial representation of the new areas of modification, that is, how the deforestation process will be based on the dynamic cover and use of the land and the elements that make up the landscape, such as the variations independent activities, it is possible to carry out future projections of deforestation in the FLONA do Jamanxim. Theories of authors representing different currents of Geography are approached to conceptualize space, landscape and dynamic modeling. In Physical Geography, one starts from Bertrand's concepts. For Quantitative Geography, Waldo Tobler was used as a basis. The discussion of Critical Geography is based on the works of Milton Santos. And Soares-Filho for spatial dynamic modeling. The methodology was divided into three main phases: 1- Processing of satellite images, using the supervised classification method through the Maximum Likelihood algorithm; 2- Processing of independent variables; 3- Stage considered the main part of the study, which consists of spatial modeling in DINAMICA EGO. As a result of the analysis of land cover and use, it was observed that there was a reduction in the area of 112.51 km² (0.87%) of primary forest, and an increase in the mosaic class of occupations (deforestation) with an area of 393.53 km², equivalent to 3% of deforested area. The main activities observed were: forest exploitation and mining. There is also a deforestation pattern classified as geometric and regular, with economic activities, such as agriculture, and mainly medium to large-scale grain and livestock monocultures, and an intermediate stage of occupation. The independent variables assume Bertrand's GTP model to observe landscape dynamics. It was observed that 0.28% of the primary forest was converted to deforestation. That is, from 2013 to 2020 deforestation is occurring at a net rate of 28% per year. And there is a high probability of transition from primary forest to a mosaic of occupations, and from forest exploitation to a mosaic of occupations to the north and south of the FLONA do Jamanxim, areas that may be associated with the implementation of roads (BR-163), and to the PDS Brasília and Vale do Jamanxim Project settlements, which consequently can impact the resilience of the landscape. Based on modeling and analysis of future scenarios, it appears that there may be a loss of 198.79 km² (1.52%) of primary forest, and a considerable increase in deforestation of 155.20 km² by 2030. The mapping of this study, it can support public policy actions by analyzing the impact of laws and identifying priority areas for government action in FLONA do Jamanxim. Based on the spatial modeling, together with the command, control and monitoring plans, it is possible to guide the socio-environmental, economic and cultural development in this UC, for the maintenance and conservation of natural assets.
Acesso aberto (Open Access)
Palm community transitions along a topographic gradient from floodplain to terra firme in the eastern Amazon
(Instituto Nacional de Pesquisas da Amazônia, 2015-03) SALM, Rodolfo Aureliano; PRATES, Anderson Sousa; SIMÕES, Nadson Ressyé; FEDER, Lisa
Palms show clear niche segregation patterns along topographic gradients in tropical forests, with some species associated to terra firme and others to seasonally flooded areas. The aim of this study was to quantitatively describe the fine-scale spatial variation within a palm community, tracking the changes in species' abundance along environmental gradients associated with a perennial stream the eastern Amazon. The study of palm communities was based on 60 forest plots in which all adult palms were counted. We found a total of 566 palms in a community containing 11 species. Furthermore, we found a significant separation in the palm community between seasonally-flooded and terra firme forests. We found a gradient with various densities of the three most abundant palm species within the first 100 m away from the flooded area. Other species were located exclusively in the terra firme forest. The abundance of the six most common species were distributed in relation to humidity gradients from floodplains to terra firme, with palm distribution from the most flood-tolerant to the least flood-tolerant palm species as follows: Euterpe oleracea, Attalea phalerata and Socratea exorrhiza (species with floodplain affinity), Astrocaryum gynacanthum, Astrocaryum aculeatum, Attalea maripa (species with terra firme affinity).