Arthropod diversity as affected by agricultural management (organic and conventional farming), plant species, and landscape context
Arthropods were inventoried in crop fields and adjacent woody hedgerows of organic and conventional farms situated in south-central Ontario, Canada. The objective was to assess the total abundance, family richness, and composition of beneficial and phytophagous arthropods in the 2 farming systems and to examine the contributions of the vegetation present and landscape features on arthropod abundance and composition. Two hundred and forty sticky traps were installed (24 sites) and 170 sweep net collections were conducted (17 sites) in crop fields and adjacent woody hedgerows of organic and conventional sites. A total of 30 807 individual arthropods belonging to 131 families were recorded during the study. No spatial autocorrelation was detected among the arthropod samples. The study showed that beneficial and phytophagous arthropod abundance differed between organic and conventional sites (only with sweep net) but family richness did not. Beneficial arthropods were more abundant in woody hedgerows, while phytophagous arthropods were more abundant in crop fields. This study also demonstrated a strong relationship between plant and arthropod composition. Habitats (total old field cover, total hedgerow length, and Shannon diversity index, all within 250 m radius) in the surrounding landscape influenced arthropod composition but were not leading factors in explaining richness and abundance. It is therefore of prime importance to consider both local factors (management practices and local vegetation) and regional factors such as landscape features as explanatory variables when attempting to explain biodiversity.
Author(s): Boutin, C; Martin, PA; Baril, A