Case study: biological pest control in vineyards
Vineyards are agroecosystems that strongly reﬂect man’s historical relationship with the land. In Piedmont (NW Italy), as in other countries, this kind of agroecosystem is facing land abandonment and agricultural intensiﬁcation. The latter process of transformation results in the progressive removal of natural landscape elements, in particular loss of woods in vineyard landscapes, thus contributing to loss of heterogeneity aﬀecting biotic communities (Agger and Brandt, 1988). Wise (1993) stresses the importance of the spider assemblages in limiting insect pests in agroecosystems and remarks on the need for research on prey limitation in natural communities and agroecosystems. The landscape structure then needs to be considered both in spatial and temporal terms (Merriam, 1988). Spatial diversity is given by the number of spider habitat types available and landscape heterogeneity by how intermingled they are. Temporally, the landscape can also be described with respect to disturbance synchronization, e.g., by season and by how large a proportion of the ﬁelds are at the same time aﬀected by management, crop rotation, land use, and husbandry (Thomas et al., 1990). Thus the landscape structure is not static. Spider communities are signiﬁcantly aﬀected by these factors, and different agroecosystem dynamics can show diﬀerent spider assemblages (Isaia et al., 2006b).