Urban landscapes need to become more biodiversity-friendly. One way to do this is to increase the quantity and quality of green spaces. Urban community or allotment gardens, in particular, can be very diverse green spaces and can serve as habitat refuges for many beneficial organisms, including natural enemies of pests. Ground-dwelling arthropod predators (GDPs) are important pest control agents. Because they are less dependent than flying natural enemies on the landscape context in which the gardens are embedded, garden management practices could be more easily manipulated to enhance their populations. We aimed to study how vegetation and ground cover of community gardens affected the abundance, species richness, and diversity of these important predators. We also assessed whether these effects changed throughout the growing season. We sampled GDPs, vegetation, and ground cover in 18 urban community gardens in the California Central Coast. We found that, in these community gardens, vegetation and ground cover did not change much throughout the growing season. This was reflected by only one significant interaction between vegetation, ground cover variables and sampling month. Crop cover had a positive effect on ants but a negative effect on other GDPs groups (but not spiders). Increased ornamental cover had a positive overall effect on spiders. We found some evidence of negative interactions between ants and spiders on other GDP groups but not between each other. It is important to investigate whether these intraguild interactions are affecting pest control services.
