Navegando por Orientadores "MOUTINHO, Paulo Roberto de Souza"

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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)
Impactos da exploração madeireira sobre a fauna de formigas e conseqüências para a remoção de sementes florestais na Amazônia Oriental
(Universidade Federal do Pará, 2001) KALIF, Kemel Amim Bittencourt; MOUTINHO, Paulo Roberto de Souza; http://lattes.cnpq.br/7277077476036269
Logging in the Amazon Forest affects approximately 1.5 million hectares of forestlands each year. These activities result in forest structural and microclimatic changes that could potentially affect diversity and animal species composition. Regeneration of these areas could be jeopardized since animals disperse most seeds. On the other hand, it is possible not to affect seed dispersal mechanisms by maintaining forest fauna integrity through the implementation of reduced impact logging techniques. By using ants as an ecologically representative animal group and integrated into the regeneration processes through dispersion and predation, this work evaluated; (1) if logging affects fauna (diversity and species composition), (2) if reduced impact logging techniques are capable of preserving it, and (3) if logging affects ants ecological efficiency in seed removal (dispersion and predation). Logging effects on ants' diversity and species composition, as well as seed removal done by these insects, were studied in three different forest areas in the municipality of Paragominas in the state of Pará. The first area was a forest that went through high impact logging (FC), the second a forest affected by reduced impact logging techniques (FB), and the third one a primary forest used as the control group (FP). Ants’ were sampled four times during 1998 using the Winkler method at four transects per area. The seed removal experiment was conducted by distributing seeds of six wood species through twelve points in each area. During the experiment the daily number of ants and other arthropods that visited the seed points was quantified. The amount of seeds removed was counted at the end of the experiment. Diversity and abundance of ant species were not affected by logging activities. However, species composition changed by 36% in FB and by 37% in FC. The Pheidole genus experienced richness and abundance reduction only in FC. Seed removal was also significantly lower (-33%) in FC compared to the ones registered in FB and FP. Ants represented 92% of all arthropods that visited the seed points in the three forest areas. The bigger seeds were the most removed ones, independently of its seed disperser adaptations and of the studied forest area. The results obtained suggest that forest logging can affect ant species composition, without affecting its diversity (except that of Pheidole). Reduced impact logging techniques have the capacity of preserving Pheidole species diversity, which guarantees seed movements similar to those of a primary forest. Nevertheless, conventional logging can reduce, both the number of species and occurrences of this genus, thus resulting in a reduced number of removed seeds. Such reduction probably jeopardizes forest regeneration after wood extraction.
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.