Structural complexity of arthropod guilds is affected by the agricultural landscape heterogeneity generated by fencerows

GHERSA, CLAUDIO M.; POGGIO, SANTIAGO L.; MOLINA, GONZALO A R

ANNALS OF APPLIED BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 168 p. 173 - 184

0003-4746

In Pampas, intensification of agricultural management imposed harsher constraints to the persistence of arthropod species within crop fields. Therefore, the arthropods that survives these conditions within fields dispersal and concentrate on nearby habitats with more abundant and varied resources, as fencerows. The areas occupied by fencerows (2 m wide beneath them) are less affected by agricultural practices sustaining more rich communities of spontaneous vegetation and associated arthropods. Here we evaluate the influence of landscape heterogeneity, generated by fencerows, in the abundance of different guilds (herbivores and natural enemies). Hence, we developed an approach based on fitting linear-mixed models to elucidate the effects of landscape heterogeneity and field position (fence and interior) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 36 crop fields.The abundance of arthropods was modulated by landscape heterogeneity, increasing the abundance of natural enemies as the landscape heterogeneity increases. Contrarily, herbivores abundance decrease with landscape heterogeneity. Arthropod communities of fencerows were structurally and functionally more complex than those present within the crop field, also decreasing the ratio herbivores/ natural enemies. Natural enemies with larger body sizes, mostly carabid beetles, were more sensitive to landscape homogenisation. Our study reveals that despite the coarse scale of the studied landscapes, fencerow density appear as important elements for structuring arthropods guilds in agricultural landscapes. In landscapes with higher density of fencerows, arthropods tend to concentrate on the fences, increasing the structural complexity of community and the predation pressure over herbivores. This structural complexity of upper trophic levels enhances the ?top-down" controls, regulating the populations of herbivores, and decreasing the probability of pest outbreaks.