COS 19-4
Landscape heterogeneity induces plant and arthropod species turnover in traditional cornfields
The expansion of the agricultural frontier through clearance of remnant forests leads to landscape simplification in low-Andean tropical regions. Previous work has shown that landscape simplification reduces the richness and abundance of herbivores and their natural enemies in crops. However, in most cases the effect of natural habitats on diversity has been evaluated for arthropods at local spatial scales, in temperate regions. Little is known about their effect in more complex crop systems, such as tropical indigenous crop systems that, besides arthropods, also maintain a high diversity of weeds. Furthermore, agricultural fields also are highly disturbed and homogenization of communities can occur through dominance of superior competitors and loss of rare species. Therefore, to conserve diversity and to develop more sustainable pest management strategies, we must understand the factors influencing patterns of species distribution and abundance in human-dominated landscapes. In particular, we are interested in understanding how remnant forest affects species distribution and diversity of plants and arthropods in traditional corn crops.
We conducted surveys of plant and arthropods in twelve traditional cornfields in Colombian Andes, during the second growing season in 2011. We estimated alpha and beta diversity to analyze changes in diversity related to the amount of forest within a radius of 250m around each cornfield. We also evaluated effects of other covariates such as soil organic matter, field former land-use, altitude and perimeter-to-area-ratio of each field.
Results/Conclusions
We found that alpha diversity of plants and arthropods in cornfields was not associated with a higher amount of native forest surrounding each field. Instead, the former land-use of each cornfield affected local diversity of plants, and plant diversity was positively related to local diversity of herbivores. However, we found that the presence of forest influenced changes on plant species composition and turnover of herbivore communities among the cornfields. We also found high beta diversity for plants and predators among the cornfields. Dominant plant species varied among fields, which led to high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields but differences in composition arose among rare species.
The indigenous crop system evaluated is a highly heterogeneous habitat due to its landscape configuration, high diversity of weeds and variations in historic land-use among the cornfields. Therefore, we should consider these three factors to conserve diversity and to develop sustainable pest management strategies in more simplified agroecosystems.