En alléodlings inverkan på markfaunan i jordbruksmark
Sammanfattning: A transition from conventional to organic agricultural practices has been shown to have positive impacts on soil and ground-living fauna. Organic farming manure is on the other hand harder for the crops to absorb than conventional fertilizers, which results in more pollutants and unsatisfactory yields. This problem is mitigated in alley cropping, an agroforestry practice where rows of trees and bushes are integrated within the agricultural fields, since much of the excess fertilizers are taken up by the bigger root systems of the woody plants. Alley cropping is also beneficial for the agricultural animal biodiversity. However, most biodiversity comparisons are made between alley cropping and conventional methods and the outcomes of alley cropping in Sweden have not been studied to a great extent. The aim of this study was therefore to investigate how earthworm (Lumbricidae), beetle (Coleoptera) and spider (Araneae) populations are affected by alley cropping versus organic practices in southern Sweden. These animal groups perform vital ecosystem services in the agricultural landscape, such as nutrient recycling and pest suppression. Abundance samples of the mentioned taxa were taken in the organic fields, as well as in both the alleys and the hedgerows of the agroforestry systems. In addition, total biomass was measured for the collected earthworms. The results indicate that the abundance of spiders and earthworms was in general higher in alley cropping and specifically in the hedgerows. Total biomass of the earthworms was also higher in the hedgerows. This is probably due to better food resources and more shelter. The beetles, on the other hand, did not seem to benefit from the hedges, which could be explained by the beetles’ better adaptation to disturbed habitats. Moreover, the hedgerows appeared to facilitate the colonization of the alleys for earthworms but not for spiders and beetles. Since no vegetation existed in the alleys, the differences between the hedgerows and the alleys were probably too big, causing the arthropods to stay in the hedgerows. More research is needed to design the hedgerows to be good overwintering habitatsbut not so good that the animals rather choose to stay there instead of colonizing the alleys during the cropping season. Nonetheless, this study concluded that alley cropping in general increases bio diversity. This, along with the other ecosystem services that the method is proven to yield, makes alley cropping a good candidate for preventing the environmental costs associated with agricultural practices.
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