How lawn mowing frequency influences soil fauna and functions in urban parks?

Background/Question/Methods

In order to guide cities in their current ecological transition, there is a paramount need to consider urban soils, which are largely understudied despite providing multiple benefits to people. Differentiated lawn management within parks (i.e. mowing frequency reduction in some sections), could potentially be a simple cost-effective strategy to better support soil biodiversity and associated ecological functions, but data remain scarce. Our study aims to determine the short- (< 1 year), mid- (2-3 years) and long-term (5-10 years) effects of lowering lawn mowing frequency on soil ecosystems. Pitfall trap and soil samples were collected during summers 2021 and 2022 in 11 sites (public parks and the botanical garden arboretum) across Rosemont La-Petite-Patrie, an eastern borough of Montreal, Qc, where differentiated management is practiced since at least 10 years. We characterized soil fauna community composition based on indicators of taxa representing micro-, meso- and macrofauna (i.e. nematodes, springtails, ants). In addition, multiple soil ecological functions were measured (available nutrients, compaction, water infiltration, carbon stocks, basal respiration and glucose-mineralization). Structural equation models will be performed to assess direct and indirect effects (mediated by soil biodiversity) of lawn mowing frequency on soil ecological functions.

Results/Conclusions

Preliminary 2021 results demonstrated no significant difference in nematode density across mowing treatments in each site with a mean density of 1167 ± 805 nematodes 100 g-1 dry soil (n=120). Heatwaves during which sampling was performed might have hindered potential mowing frequency effects as dry soils were likely limiting to nematode communities that depend on soil water content to live. Forthcoming results on nematode richness (assessed with metabarcoding of bulk nematode samples) and from 2022 samples will be necessary to confirm if lawn mowing frequency had no impact on soil microfauna. Further preliminary results on soil compaction, water infiltration and springtail diversity will be presented to explore if soil functions and/or epigeic fauna living on soil surface are more sensitive to lawn mowing frequency than deeper-dwelling soil fauna. By establishing feedback effects between soil biodiversity and society (lawn management, soil benefits), this project will allow to better integrate belowground facets in urban forest management and ultimately help manage more resilient cities facing global change.