Agroecosistem roden communities in Río Cuarto, Córdoba, Argentina.

Abstract

Rodent sampling was carried out in fields of Río Cuarto Department, Córdoba Province, particularly in cultivated land.
Equitability, diversity and species richness indices,proved higher inenvironment undergoing mild antropic disturbance, than in land under cultivation or devoted to cattle raising.
Cropland differs from natural habitat more than field borders, which in turn may be discriminated as a function of adjacent land use. Thus, Calomys predominates in cultivated fields, whereas Akodon dolores and Oligoryzomys flavescens are dominant in natural habitat. Wider borders adjoining less disturbed areas may be interpretad as great islands near the continent, whose similarity indices closely follow those of the above areas. In contrast, highly disturbed borders, due to cattle action or because they are limited by cultivated fields, exhibited an increase in Calomys density, together with a drop or disappearance of A. dolores. Habitat amplitude showed maximum values for C. musculinus, closely followed by A. dolores, and with a greater margin, C. laucha. The occurrence of C. musculinus both in borders and in cropland explains its leading habitat amplitude. As more types of longitudinal habitat have been identified than cropland ones, there is some bias in assigning to A. dolores an habitat amplitude value close to C. musculinus, and much higher than C. laucha, in spite of the fact than A. dolores and C. laucha are limited to only one major kind of habitat, namely stable environments and borders for the former, and cultivated or pastured fields for the latter. Figure 2 shows trends of the ecologic regression.
Thus when natural fields are used for crops or cattle raising the Calomys species predominates, particularly C. musculinus at first, although continual disturbances favour C. laucha. When crops are sown density falls due to agricultural machinery and the loss of protective coverage. As crops ripen Calomys still predominate in higher densities. After Harvest the cycle restarts if sowing takes place. However if the land is allowe to rest, A dolores becomes the leading species as in natural lands.