Factors driving soil Collembola and earthworms in Mediterranean urban parks: feedbacks from Montpellier and Naples

Within the cities, soil biodiversity is preserved in few sites, still unsealed by cement or paved roads, like urban parks, family gardens, or urban agricultural areas. These areas provide crucial ecosystem services (Haase et al. 2014). Urban parks in particular provide aesthetic and recreational services, regulate the water cycle, modify local climate, produce O2 and, filtering air pollutants, improve citizens health (Lorenz and Lal 2009). Besides, urban parks are also important habitats for biodiversity (Nielsen et al. 2014), which being valuable by itself provides also a range of other services (Haase et al. 2014). However, soil biodiversity is currently poorly known, especially in Mediterranean cities, and relatively uninvestigated are the environmental factors determining its structure and persistence. To fill this gap, we explored the environmental factors affecting soil biodiversity of Collembola and earthworms (good indicators of soil biological quality), in parks of two cities: Naples (Italy) and Montpellier (France). The investigated factors were soil inorganic pollutant contents, vegetation cover (with or without canopy) and urban landscape features. In addition, we focused on the effects of management practices, especially of turfs, studying both conventionally managed systems (high energy inputs, including irrigation and regular cuttings with exportation of organic matter) and ecologically managed systems (low energy inputs, with only 1 or 2 cutting per year and mulching). Collembola communities are both strongly affected by urban park management practices. In particular, the canopy cover was the main determinant of the Collembola community structure, which strikingly differed between areas with or without canopy. Landscape features, followed by soil local conditions, like the presence of litter and soil porosity, also influenced Collembola communities. Abundance of earthworms was greater in ecologically managed systems compared to conventionally managed systems. Our findings may help city planners to promote soil biodiversity by creating or correctly managing urban parks.