Estudo de indicadores ambientais e de padrões de uso do espaço por pequenos roedores silvestres em áreas de campo alterado na apa do Banhado Grande, Viamão, RS: subsídios para conservação e para recuperação de áreas degradadas

Abstract

The space of the landscape most often utilized by fauna joins the most favorable ecological, or least extreme, conditions for its establishment and maintenance. The spatial and temporal heterogeneity of the habitats affects the faunistic patterns of abundance and distribution, prompting populations to exploit the physical space differently. Monitoring makes up the main part of environmental control and studies for the conservation of its inheritance. Its indicators are essential components in decision-making, because they allow us not only to create scenarios and reference environments that point out changes and conditions of the environment but also to measure or follow the results of a decision taken. Periodic evaluations of the natural behavior of biotic elements (fauna of small non-flying mammals and phytostructural of the habitat volume) and abiotic elements (level of soil moisture) were carried out in the Protected Environmental Area (PEA) of Banhado Grande, in the municipality of Viamão, RS, such that both monthly variations patterns and the use of habitats by fauna allow establish local environmental references (ER’s) of the study area and constituted in technical knowledge to help management strategies and faunistic conservation. Monthly evaluations were carried out in areas of altered fields, between September 2010 and August 2011, totaling 12 field expeditions. Along three transects, 30, 15 and four sampling points were defined for small non-flying mammals, level of soil moisture, and phytostructural of the habitat volume, respectively. There was a high rate of faunistic use of environments with vegetation between 0.388 m³/4 m² and 1.550 m³/4 m², and levels of soil moisture between 9.030% and 21.747%. Calomys cf. tener and Oligoryzomys flavescens demonstrated a preference for lower vegetation strata, on average, and the capacity of recognizing a part of fields as a herbaceous matrix. C. cf. tener even made a distinction between environments with different levels of soil moisture, preferring drier places. Calomys laucha and Deltamys kempi potentially select micro-habitats, respectively with low phytostructural of the habitat volume (lower vegetation, on average) and high levels of soil moisture. C. laucha appears to select micro-habitats depending more on the structure of vegetation than on the presence of items that recognizably compose its diet. We also found a positive and significant correlation between level of soil moisture and number of captures, with moderate fit of the model. Thus, a cause and effect relationship was found between the parameters evaluated, indicating that the fauna of small non-flying mammals is influenced by natural oscillations of percentages of soil moisture. The narrow range of tolerance to variation in volume of vegetation, found for C. laucha and C. cf. tener, as well as the concentration of recordings of O. flavescens in 10 environments with lower volume of vegetation, or more humid ones in the case of D. kempi, suggests the high bioindicator efficiency of these species in the area. The monthly environmental references obtained between September 2010 and August 2011, for the parameters analyzed showed, in evaluation of non-inclusion in confidence intervals established from monthly sampling data, significant differences in the majority of the comparisons, corroborating their potential for applied use.