Dynamics of magnesium in rangeland areas of Southeastern region of the State Rio Grande do Sul/Brazil. 2. Correlations

We aimed to evaluate the dynamics of magnesium (Mg) in the soil - plant – animal chain. It was conducted in two natural rangeland areas on two types of undisturbed (virgin) soils (medium/clayey texture) in the Serra do Sudeste (Rio Grande do Sul State, Brazil). In each of these areas, 12 animals (heifers) were kept under continuous extensive grazing for twelve months without mineral supplementation. Every month, samples of soil and vegetation were collected at 16 fixed points (radius: 25 m) as well as blood serum from each of the animals in each area for the determination of Mg and other minerals levels. The data were analyzed using the analysis of variance, decomposition of the annual variation of the response variables and periodic regression (harmonic analysis) for adjustment of function to express this variation. The relationship of Mg with other variables within the links of the soil-plant-animal chain is influenced by some factors such as physicochemical and biological soil reactions, floristic composition and environmental conditions. In natural non perturbed rangeland areas the organic matter is the main colloid of the soil for the availability of magnesium to plants and, consequently, to the animals.