Impact of nutrient cycling on food web stability

Nutrient cycling is fundamental to ecosystem functioning. Despite recent major advances in the understanding of complex food web dynamics, food web models have so far generally ignored nutrient cycling. However, nutrient cycling is expected to strongly impact food web stability and functioning. To make up for this gap, we built an allometric and size structured food web model including nutrient cycling. By releasing mineral nutrients, recycling increases the availability of limiting resources for primary producers and links each trophic level to the bottom of food webs. We found that nutrient cycling can provide more than 50% of the total nutrient supply of the food web, leading to a strong enrichment effect that promotes species persistence in nutrient poor ecosystems but leads to a paradox of enrichment at high nutrient inputs, i.e. to destabilisation. In addition to this enrichment effect, the presence of recycling loops linking each trophic level to the basal resources stabilises species biomass dynamics in food chains but has only weak effects in complex food webs. This new model open perspectives for better linking studies on food web dynamics to ecosystem processes.