Earthworms of a Silvopastoral System of Northwestern State of Paraná, Brazil

Abstract

Earthworms are known to increase soil bulk density, soil porosity, mixing of organic matter, and to strengthen aggregation of soil particles. They perform important functions in the maintenance and stabilization of the soil matrix. So, earthworms can be used as indicators of the quality and health of soils. More emphasis on studying underground components, such as earthworms, is required in order to better understand the mechanisms of silvopastoral systems function. The purpose of this study was to examine the presence and the distribution of earthworms in a silvopastoral system (SSP) with Grevillea robusta trees, planted in rows, in comparison with a pasture without trees (PNA). Sampling in six areas (five in SSP and one in the PNA) was carried out in October, 2005 at Cianorte, Parana, Brazil. The samples (n=162) were collected at three distances from the tree rows and/or bulk terraces. Significant variation in earthworm quantity was found between the two pastures conditions. Sample variance was higher than average in all areas, indicating trend to negative binomial distribution and, consequently, to aggregate distribution of earthworms. The average number of earthworms and cocoons were higher in the PNA and we found significant differences (p < 0.01) between SSP and PNA employing a contrast analysis. The distribution of individuals were positively influenced by trees, whereas the number of individuals seemed to be influenced by the capacity of some species to colonize environments with scarce resources. So, to complement the present study it will be necessary to characterize the spatial and temporal distribution of individuals and species. Furthermore, the understanding of the interaction between Grevillea obusta and the population of annelids depends on studies of litterfall, other organisms and microclimatic conditions under canopies.