Microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants in lead contaminated soil

The goals of this study were to evaluate the microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants (Caesalpinia ferrea, Mimosa tenuiflora and Erythrina velutina) in lead contaminated soil from the semi-arid region of northeastern of Brazil (Belo Jardim, Pernambuco). Dilutions were prepared by adding lead contaminated soil (270 mg Kg-1) to uncontaminated soil (37 mg Pb Kg soil-1) in the proportions of 7.5 percent, 15 percent, and 30 percent (v:v). The increase of lead contamination in the soil negatively influenced the amount of carbon in the microbial biomass of the samples from both the dry and rainy seasons and the metabolic quotient only differed between the collection seasons in the 30 percent contaminated soil. The average value of the acid phosphatase activity in the dry season was 2.3 times higher than observed during the rainy season. There was no significant difference in the number of glomerospores observed between soils and periods studied. The most probable number of infective propagules was reduced for both seasons due to the excess lead in soil. The mycorrhizal colonization rate was reduced for the three plant species assayed. The inoculation with arbuscular mycorrhizal fungi benefited the growth of Erythrina velutina in lead contaminated soil.

Evaluation of pasture soil productivity in the semi-arid zone of Brazil by microbial analyses / Avaliação da produtividade de um solo de pastagem na zona do semi-árido através de análises microbianas

The productivity of a pasture soil (caatinga) located in the region of São João do Cariri, PB, Brazil was evaluated based an the following microbiological parameters: biomass (measured by fumigation-incubation method), activity (estimated from basal respiration and cellulose decomposition rate), qCO2, and Cmic : Corg ratio. This analysis demonstrated that livestock management in the 'caatinga' is probably causing environment damage by affecting the soil properties, reducing the microbial biomass and soil respiration and increasing the qCO2, affecting the recovery of this ecosystem.

A produtividade de um solo de pastagem (caatinga) na região de São João do Cariri, PB, Brasil foi avaliado através dos seguintes parâmetros microbiológicos: biomassa (medidas pelo método de fumigação incubação), atividade (estimada com base na respiração basal e taxa de decomposição de celulose), qCO2 e a razão Cmic : Corg. Estas análises demonstraram que o manejo de rebanhos na caatinga pode causar danos a este ambiente devido a modificações das propriedades do solo como diminuição da biomassa microbiana e da atividade e aumento do qCO2, afetando a recuperação deste ecossistema.