Navegando por Assunto "Floresta de Transição Amazônia-Cerrado"

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Acesso aberto (Open Access)
Efeitos do fogo recorrente na serrapilheira: consequências para artrópodes, decomposição e mineralização de carbono e nitrogênio em uma floresta de transição da Amazônia
(Universidade Federal do Pará, 2008) SILVEIRA, Juliana Miranda da; MOUTINHO, Paulo Roberto de Souza; http://lattes.cnpq.br/7277077476036269
Arthropods play an important role in ecosystem functioning, participating in nutrient cycling, decomposition and the breaking up and mixing of the leaf litter. Forest fires are increasing across the Amazon basin, and destroy the litter layer and kill the invertebrates that live within it. The objective of this thesis is to investigate how recurrent fires affect these processes, investigating the abundance and density of leaf-litter arthropods and the rate of decomposition of organic material and the mineralization of C and N, in a transitional Amazonian forest in the municipality of Querencia in the state of Mato Grosso, Brazil. The study was conducted in 50 ha of primary forest (500 x 1000 m) that was experimentally burned every year from 2004, and an unburned primary forest control of the same size. The arthropods were collected in 40 pitfall traps and 40 funnel Berlese traps, located randomly. The collections were undertaken in February, April (wet season), June, and August (dry season) of 2007, after the third experimental burning. The arthropods were identified to the level of Order, and the ants were identified to the level of Genera. The decomposition study was undertaken using 480 litter bags, randomly distributed with 240 in each plot, 4 months after the last burns. The litter bags were constructed with 2 mm nylon mesh (fine mesh), and 50% of them had 1 cm² holes cut in their sides (coarse mesh). 10g of dry leaves were placed in each litter bag, and 30 bags were collected from each plot every 2 months, equalling 2 collections in the wet season and 2 in the dry season. The litter bags were dried in an oven, and litter was weighted again to calculate decomposition. The difference between inicial and final weight showed the decomposition rate. Ten litter bags were selected randomly from every collection, mesh size, and plot, and subjected to a C and N analysis. The arthropods demonstrated strong seasonal differences. Springtails were less abundant and ants were more abundant in the dry season. Along with the seasonal effects, arthropods had diverse effects to the recurrent fires: Orthoptera were always more abundant in the burned plots in all post-fire samples when compared to controle plot. In general, macro-predators (ants, beetles, and others) were more abundant in the burned forest, while the ecosystem engineers and decomposers (cockroaches, Acaridae, and others) were less abundant in the burned forest, when compared to control plot. Ants were more diverse in the dry season, and also showed strong seasonal differences in composition. There was also a marked difference in ant diversity between the two plots, and fires favoured generalists ants. The decomposition rate in the burned forest were lower than in the control, and the fine mesh litter bags had a lower rate of decomposition than those with holes cut in their sides (coarse mesh). The level of C and N was also different between the plots, and the C/N ratio (indicating microbial activity) was stable over time in all post-fire collections, while the C/N ratio in the control plot declined gradually during the 4 collections. These results indicate that fire modifies the leaf-litter fauna, affecting the abundance and composition of various taxonomic groups. The fine mesh litter bags indicate that the exclusion of macroarthropods reduces the rate of organic matter decomposition and that microarthropods are more affected by fires. Fire also reduces the mineralization of C e N as C/N was stable in burned plot. Overall, this study shows that recurrent fires have strongly effects on leaf-litter fauna and nutrient cycling in Amazonian transitional forests.
Acesso aberto (Open Access)
Estudo da comunidade de pequenos mamíferos não-voadores, sob efeito do fogo e da borda, em área de floresta de transição Amazônia-Cerrado, Querência, MT
(Universidade Federal do Pará, 2008-10-10) SANTOS, Paulo Guilherme Pinheiro dos; OLIVEIRA, Ana Cristina Mendes de; http://lattes.cnpq.br/1199691414821581
The deforestation of the Amazon, caused by farming and agribusiness activities in the northern state of Mato Grosso, has committed Transition Forests Amazon-Savanna, before the biodiversity of these areas is known by researchers. The fauna of small non-flying mammals is part of the little-known groups in the region, and may be suffering impacts of human activities, primarily effect of fire, used for cleaning of pastures and deforestation for the soybean plantations. This study characterized the diversity of small mammals not flying in an area of Amazon forest-savannah transition in the northern state of Mato Grosso and investigated the effect of fire and the effect of edge on this group of fauna. Two areas of 150 hectares were sampled, a preserved and another under impact of fire, with 183 traps of the type live-trap for three years in two season (dry and rainy seasons). The method used was the capture-mark-recapture. The sampling effort was 23,424-traps night. 390 individuals were captured with a successfully capture of 1.66%. A total of 11 species were caught, 6 rodents and 5 marsupials. Hylaeamys megacephalus was the most abundant species. The diversity of small mammals in the study area was more related to the Savanna than Amazon. In relation to fire, the species richness was not statistically different, but the abundance was significantly higher in transects located in an area without fire. Two distinct groups of transects were characteristic depending on the presence or absence of fire based on the composition of small mammals. The abundance of Hylaeamys megacephalus was significantly higher in transects that suffered no impact from fire. Regarding the effect of edge in Area 2, despite the richness of species was not significantly different, the abundance was significantly higher regarding distance from the border. Already in Area 1, nor richness nor abundance was statistically different regarding distance from the edge. This fact could be masked by both the direct and indirect effect of experimental fire on small mammals. When considered together fire and distance from the border, the relationship between them became clearer, since all transects sampled under effect of the fire had minor abundances. The population size of Hylaemys megacephalus was calculated over five seasons (dry and wet) in the area without influence of fire, and the rainy season of 2006 was statistically different peak and the other that growth can be explained by the “Alle effect”. There was no statistically significant differences in the structure of the community of small non-flying mammals between the dry and rainy seasons. This work contributed to the search of mammal knowledge at this region threatened by human pressures.
Acesso aberto (Open Access)
Influências dos ninhos de saúva (Formicidae: Attini) na nutrição, crescimento e proteção da vegetação contra o fogo, em uma floresta de transição Amazônia-Cerrado
(Universidade Federal do Pará, 2008) CARVALHO, Karine Santana; STERNBERG, Leonel; http://lattes.cnpq.br/2673570808369028; MOUTINHO, Paulo Roberto de Souza; http://lattes.cnpq.br/7277077476036269
The leaf-cutting ant nests are important natural disturbances which may create mosaics of certain types of vegetation and affect the structure and composition of Neotropical ecosystems. So, this study evaluated the effects of leaf-cutting ant nests (Atta spp.) on dynamic of vegetation growth in a Amazon-Cerrado transitional forest submitted to subsequent fire events, in south Amazon basin, Mato Grosso State, Brazil. Specifically, it was evaluated the effects of the nests on: (1) vegetation growth and nutrition; (2) vegetation protection against fire and (3) the forest regeneration pos-fire. The nests and associated vegetation (within a 10-meter radius of the nests) established in 150-hectare areas of transitional forest were mapped and monitored in order to determine such effects. These areas subdivided in 50-ha parts with different treatments: triannual fires, annual fires and fire protection (control) take part in the project “Savannization” coordinated by Amazon Environmental Research Institute – IPAM. The experiments about the effects of the nests on vegetation growth and nutrition indicated that plants next the nests have a facilitated nutrient absorption and therefore they present a higher foliar concentration of Phosphorus. Consequently, it was registered a higher growth in diameter of stem to these plants when compared to those far from the nests. The nests worked as active firebreaks (due to accumulation of land on mound resulting from leaf-cutting ants diggings) reducing the total burned area around them, mainly in areas with high number of nests and protecting the surrounding vegetation from the mortality by fire. In opposition to these benefits, it was verified higher herbivory of seedlings and the removal of seeds by leaf-cutting ants in areas with high density of active colonies, a result which compromise the early stages of pos-fire forest succession. This study shows the importance of leaf-cut ants in the redistribution and nutrient recycling and demonstrates, for the first time, the vegetation protection against fire, by their nests. On the other hand, it also shows that anthropic disturbances, such as fire, increase the leaf-cut ant population. This can stop the pos-fire forest regeneration. Considering this study, it can predict that natural environments may have the vegetation growth accelerated due to the presence of leaf-cut ant nests, but in disturbed environments the action of leaf-cut ants may be the main threat to the original vegetation regeneration. So, it can conclude that the effects (beneficial or harmful) of the leaf-cut ants depend on the level of disturbance or maturity of biome in which their nests are established.
Acesso aberto (Open Access)
Setting boundaries: Environmental and spatial effects on Odonata larvae distribution (Insecta)
(2015-03) MENDES, Thiago Pereira; CABETTE, Helena Soares Ramos; JUEN, Leandro
Environmental characteristics and spatial distances between sites have been used to explain species distribution in the environment, through Neutral (space) and Niche theory (environment) predictions. We evaluated the effects of spatial and environmental factors on Odonata larvae distribution along the Suiá-Missú River Basin, state of Mato Grosso. We tested the hypotheses that (1) the environment is the main factor structuring the community due to its ecophysiological requirements; and (2) the pattern, if present, is clearer for Zygoptera. Samples were made in 12 sites on the Suiá-Missú River Basin in three seasons (2007/2008), with a total of 1.382 Odonata larvae, comprising 10 families, 51 genera and 100 morphospecies. The Anisoptera were more abundant than Zygoptera, comprising 81% of all specimens. The environment affected Zygoptera (R=0.291; p=0.007) and was the main factor structuring the assembly. Thus, Niche theory was confirmed. The absence of this effect on Anisoptera may be due to the ecophysiological adaptations that enable it to occupy different habitats. Zygoptera larvae are indicators of changes in habitat structure. The effects of environmental variables on larvae ecology emphasize the strong relationship between these organisms and environmental integrity.