Cauliflower strip cropping promotes ground-dwelling arthropod richness and spider abundance

Samenvatting

While large-scale agriculture is an important driver of biodiversity loss, diversified agricultural cropping systems may have potential to support farmland biodiversity. Strip cropping is a form of crop diversification in which crop strips are alternated in the same field and thereby increasing in-field crop heterogeneity and edge-density while using existing farm machinery. Although strip cropping may provide more diversity in habitat, food, and shelter at small spatial scales, it is still unknown how arthropod communities respond to a variety of strip widths of intensively managed vegetable crops, and whether strip cropping can provide nearby refuge sites for arthropods during and after harvest. We studied responses of the ground-dwelling arthropod community to strip widths of 6, 12, 24 and 48 m, both pre- and post-harvest. The study was conducted in cauliflower strips in a large-scale, commercial organic strip cropping field in 2018 and 2019. The cauliflower strips were bordered by annual flower strips on one side and by grass-clover (year 1) or potato (year 2) on the other side. Increasing strip width was associated with lower spider activity density and lower richness of the ground-dwelling arthropod community, and higher rove beetle activity density. Ground beetles showed variable responses to strip width depending on genus and year. Ground beetles of the genus Harpalus showed negative responses to increasing strip width in both years and genera Bembidion and Pterostichus showed positive responses to increasing strip width in 2019. Crop harvest had a negative influence on ground-dwelling arthropod activity density and community richness, and this effect was more pronounced in narrow strips than in wider strips. Our results indicate that strip cropping cauliflower can support ground-dwelling arthropod community richness and activity density of certain species groups in large-scale agricultural fields, but does not enhance short-term post-harvest recolonization.