Maria Elizabeth Fernandes Correia

Caracterização da fauna edáfica em sistemas de manejo para produção de forragens no Estado do Piauí

Resumo - O objetivo desse trabalho foi avaliar a distribuicao da fauna em funcao da umidade do solo em diferentes sistemas de manejo para a producao de forragens com capim-Tifton 85 (Cynodon dactylon Pers. x C. niemfuensis Vanderys), capimTanzânia (Panicum maximum Jacq. cv. Tanzânia), capim-Andropogon (Andropogon gayanus Kunth), Leucena (Leucaena leucocephala (Lam.) R. de Wit.) tendo como controle uma Mata dos Cocais. A coleta da fauna foi feita utilizando-se armadilhas do tipo Pitfall em duas epocas do ano: setembro de 2007 e marco de 2008, periodo seco e chuvoso, respectivamente. Os sistemas com capim-Tifton, capim-Tanzânia e Leucena mostraram maior numero de individuos nos dois periodos avaliados. A queimada ocorrida no capim-Andropogon antes da primeira coleta resultou em uma reducao na abundância e diversidade da fauna edafica. Os maiores valores em riqueza, diversidade e uniformidade de fauna foram obtidos na amostragem realizada no periodo umido. A mata mostrou maior diversidade e equitabilidade nos dois periodos avaliados. Em situacao de estresse hidrico alguns grupos como Formicidae e Collembola predominaram nos sistemas de manejo diminuindo a uniformidade, enquanto no periodo umido varios grupos mostraram boa representatividade o que favoreceu a uniformidade. A analise multivariada de componentes principais evidenciou que os sistemas com mata, capim-Tifton e capim-Tanzania e Leucena mostraram associacao com varios grupos da fauna edafica nos dois periodos avaliados enquanto que o sistema com capim-Andropogon, que sofreu queimada, apresentou afinidade apenas com o grupo Heteroptera, no periodo seco. Plavras-chave - Leguminosa arborea. Pastagem. Sazonalidade.

Soil fauna as an indicator of soil quality in forest stands, pasture and secondary forest

The interactions between soil invertebrates and environmental variations are relatively unknown in the assessment of soil quality. The objective of this study was to evaluate soil quality in areas with different soil management systems, based on soil fauna as indicator, in Alem Paraiba, Minas Gerais, Brazil. The soil invertebrate community was sampled using pitfall traps, in the dry and rainy seasons, from areas with five vegetation types (acacia, mimosa, eucalyptus, pasture, and secondary forest). The abundance of organisms and the total and average richness, Shannons diversity index, the Pielou uniformity index, and change index V were determined. The fauna was most abundant in the areas of secondary forest and mimosa plantations in the dry season (111.3 and 31.7 individuals per trap per day, respectively). In the rainy season, the abundance of organisms in the three vegetation types did not differ. The highest values of average and total richness were recorded in the secondary forest in the dry season and in the mimosa stand in the rainy season. Shannons index ranged from 1.57 in areas with acacia and eucalyptus in the rainy season to 3.19 in the eucalyptus area in the dry season. The uniformity index was highest in forest stands (eucalyptus, acacia and mimosa) in the dry season, but higher in the rainy season in the pasture and secondary forest than in the forest stands. The change index V indicated that the percentage of extremely inhibited groups was lowest in the area with mimosa, both in the dry and rainy season (36 and 23 %, respectively). Of all forest stands, the mimosa area had the most abundant soil fauna.

Aporte e decomposição da serapilheira e produção de biomassa radicular em florestas com diferentes estágios sucessionais em Pinheiral, RJ

The aim of this study was to evaluate litter input and decomposition and root biomass of three forest fragments at different successional stages (advanced, medium and initial) in Pinheiral Municipality, in the state of RJ, Brazil. To evaluate litter input, 10 conic collectors were installed in each fragment. The root biomass was quantified by monolith method in two periods (wet and dry) at depths of 0-10, 10-20 and 20- 30 cm , and 10 samples were collected in each area. To evaluate the decomposition rate in each area, 12 litter bags were distributed. No significant differences were observed for litter input between the areas, but there was a tendency to increase litter input with successional evolution. No significant differences were observed for seasonal litter input between areas during the year, but there was a small increase in the months of July and August. At the advanced stage, litter input could be grouped into two periods: February to July, with lower values; and August to January, with higher values. The leaf fractions and reproductive material input were reduced, while branch and other fractions increased with succession. For litter decomposition, the intermediate stage showed the lowest decomposition constant (k) ( 0.0038 g g -1 day -1 ) and the highest half life time (182 days) , followed by the initial ( 0044 g g -1 day -1 and 154 days) and advanced ( 0.0064 g g -1 day -1 and 108 days) stages. The root biomass in different areas and depths for both two periods studied showed higher values in the advanced stage, followed by the intermediate stage and the lowest values were found in the initial stage. The seasonal root biomass difference occurred mainly in the intermediate stage, with higher values in June.

Ecotoxicology of mercury in tropical forest soils: Impact on earthworms

Mercury (Hg) is one of the most toxic nonessential trace metals in the environment, with high persistence and bioaccumulation potential, and hence of serious concern to environmental quality and public health. Emitted to the atmosphere, this element can travel long distances, far from emission sources. Hg speciation can lead to Hg contamination of different ecosystem components, as well as biomagnification in trophic food webs. To evaluate the effects of atmospheric Hg deposition in tropical forests, we investigated Hg concentrations in earthworm tissues and soils of two Forest Conservation Units in State of Rio de Janeiro, Brazil. Next, we performed a laboratory study of the biological responses (cast analysis and behavioral, acute, chronic and bioaccumulation ecotoxicological tests) of two earthworms species (Pontoscolex corethrurus and Eisenia andrei) to Hg contamination in tropical artificial soil (TAS) and two natural forest soils (NS) spiked with increasing concentration of HgCl2. Field results showed Hg concentrations up to 13 times higher in earthworm tissues than in forest soils, while in the laboratory Hg accumulation after 91-days of exposure was 25 times greater in spiked-soils with 128mgHgkg-1 (dry wt) than in control (unspiked) soils. In all the toxicity tests P. corethrurus showed a higher adaptability or resistance to mercury than E. andrei. The role of earthworms as environmental bioremediators was confirmed in this study, showing their ability to greatly bioaccumulate trace metals while reducing Hg availability in feces.

Characterization of soil fauna under the influence of mercury atmospheric deposition in Atlantic Forest, Rio de Janeiro, Brazil

The increasing levels of mercury (Hg) found in the atmosphere arising from anthropogenic sources, have been the object of great concern in the past two decades in industrialized countries. Brazil is the seventh country with the highest rate of mercury in the atmosphere. The major input of Hg to ecosystems is through atmospheric deposition (wet and dry), being transported in the atmosphere over large distances. The forest biomes are of strong importance in the atmosphere/soil cycling of elemental Hg through foliar uptake and subsequent transference to the soil through litter, playing an important role as sink of this element. Soil microarthropods are keys to understanding the soil ecosystem, and for such purpose were characterized by the soil fauna of two Units of Forest Conservation of the state of the Rio de Janeiro, inwhich one of the areas suffer quite interference from petrochemicals and industrial anthropogenic activities and other area almost exempts of these perturbations. The results showed that soil and litter of the Atlantic Forest in Brazil tend to stock high mercury concentrations, which could affect the abundance and richness of soil fauna, endangering its biodiversity and thereby the functioning of ecosystems.

Influência do sistema de plantio sobre atributos dendrométricos e fauna edáfica, em área degradada pela extração de argila

The intercropping of Eucalyptus with legumes can promote an improvement of soil biological quality in degraded areas and also be advantageous for the species of the consortium. The aim of this study was to evaluate the influence of planting systems (monoculture and consortium) of Acacia mangium (AM), Sesbania virgata (SV) and Eucalyptus camaldulensis (EC) on the biological characteristics of the plants (dendrometric attributes) and specifically on the fauna in the litter and the surface soil layer (0-0.05 m). An experiment in a randomized block was conducted with six treatments and three replications. The treatments used to evaluate the dendrometric attributes were: 100 % EC and 100 % AM; 50 % EC + 50 % AM; 50 % EC + 50 % SV; 50 % AM + 50 % SV). To evaluate the soil fauna, biological characteristics were assessed in treatments with: 100 % EC; 100 % AM; 100 % SV; 50 % EC:50 % SV; and 50 % AM:50 % SV. Forty-eight months after planting, the height (H) and diameter at breast height (DBH) of the species EC and AM were measured, and estimates of basal area (BA) and wood volume with bark per tree (WBT). The abundance and diversity of the soil fauna were evaluated in leaf litter and soil (0.0-0.05 m). When intercropped with legumes, the DBH, BA and WBT of EC were higher. In contrast, for AM these variables were unaltered when intercropped with EC and SV. Plantations of EC-SV consortium promoted higher total abundance of organisms and highest values of Shannon diversity and evenness indices, especially with regard to the litter compartment.

Análise multivariada de atributos pedológicos e fitossociológicos aplicada na caracterização de ambientes de cerrado no norte de Minas Gerais

The Cerrado is one of the main Brazilian expanding regions for agriculture, but the fragility of its ecosystems limits the support capacity for agriculture activities, jeopardizing the preservation of its biodiversity. The objective of this study was to define local patterns of edaphic and vegetation characteristics, of a small watershed in Rio Pardo de Minas municipality (Minas Gerais State, Brazil), as the basis for the sustainable planning for local usage. For such, techniques of phytosociological survey and soils were applied and associated to multivariate statistical procedures, dendrogram and PCA, in order to correlate the spatial distribution of groups of species with soil attributes. The results showed the classification of the environments into two groups, based on the nature of parent materials: arenitic-quartzitic and sandy-clayey and clayey sediments. The selection of variables using the multivariate analysis was able to discriminate the environments represented in the phytosociological plots. The patterns identified by the local farmers corresponded, in general, to the variations in the floristic and phytosociological parameters and edaphic attributes. The absolute density , basal area, Shannon index and the granulometric fractions were the determinant parameters in the differentiation of the environments.

Ecotoxicity of mercury to Folsomia candida and Proisotoma minuta (Collembola: Isotomidae) in tropical soils: Baseline for ecological risk assessment.

Mercury (Hg) is a highly toxic nonessential trace metal. Despite its natural occurrence in the Earths Crust, its concentrations have been steadily increasing in the environment due to anthropogenic sources. Recent studies have showed great concern about soil fauna, once the potential adverse effects of mercury concentrations in the environment of these invertebrates are still poorly understood, especially when linked to forest soils and tropical biota. Different collembolan species can show distinct toxicity effects to the contaminants, impairing its developing lifelong and affecting its diversity and abundance in the environment. Laboratory studies were performed to evaluate the ecotoxicity of Hg(II) to collembolan species collected in Brazil, Proisotoma minuta (autochthonous) and Folsomia candida (allochthonous), as a tool to predict effects in ecological risk assessment of tropical regions. Behavioral, acute and chronic tests were carried under temperatures of 20°C and 24°C using two test soils, natural and artificial, spiked with increasing mercury concentrations. F. candida was more sensitive to mercury contamination than P. minuta, presenting the most restrictive values of EC50 and LC50. Reproduction was a considerably more sensitive endpoint than avoidance and mortality. The 28-day lower EC50 values were found in chronic tests for F. candida in natural soil to 24°C (3.32mgHgkg(-1)), while for P. minuta was in tropical artificial soil to 20°C (4.43mgHgkg(-1)). There were similarity for each collembolan species to respond at the Hg(II) effects when exposed at 20°C and 24°C. F. candida can be suitable as a bioindicator species to mercury ecotoxicity tests in tropical forest soils.

Impacto do monocultivo de café sobre os indicadores biológicos do solo na zona da mata mineira

This study aimed to evaluate the effect of the coffee monoculture in an oxisol of the Zona da Mata (MG, Brazil) through changes in total organic carbon in the soil and microbiological indicators of soil quality. Four areas were selected: a) culture of coffee (Novo Mundo) during 22 years (C22); b) culture of coffee (Catuai) during 16 years (C16) c) secondary forest with approximately 30 years old (M30) and d) secondary forest during 40 years (M40). Soil samples were collected in the depth of 0-10cm in January, April, July and October. The biological variables studied were sensitive to characterize changes in soil quality from coffee monoculture. The results varied with the season and climate. In the driest period, a reduction in the values occurred, affecting more drastically the coffee systems. The index of soil quality showed that the C22 system presented greater loss of quality in relation to the M40, indicating less sustainability commitment.

Response of soil mites to organic cultivation in an ultisol in southeast Brazil

Soil-dwelling mites of four plots under organic management were investigated in April and December 1998 and in December 1999. Their populations were compared with mite populations in a pasture and forest in the vicinity. It was observed that there was always an initial reduction in the populations of soil mites and in the activity of the epigeic forms whenever a plot was opened up and disturbed mechanically in preparation for cultivation, irrespective of previous organic inputs. With time, the densities and activities of mites recovered under organic management. The uropodine and oribatid mites in particular benefited more from organic management than gamasine and actinedid mites. Uropodine mites increased tremendously under banana where there was fresh cow dung manure. Oribatid mite species Nothrus seropedicalensis and Archegozetes magnus were dominant in organic plots where the soil was moist and temperatures were lower than the ambient. Protoribates rioensis was dominant in organic plots where the soil was drier and temperatures were higher than the ambient. Galumna was the most active oribatid taxon on the floor of all plots, with the highest activity recorded under maracuja and in pasture plots. The results suggest that while densities and activities of soil mites increased in the organic plots, the community structure and recruitment period of oribatid mites were altered. Oribatid mite diversity was higher in the organic plots than in the pasture but lower than in the forest, where Belba sp. and many Eremobelboid brachypiline genera were present, but absent in the organic plots and pasture.