Ecosystem-level stabilizing effects of biodiversity via nutrient-diversity feedbacks in multitrophic systems

TL;DR

This study introduces a new mechanistic model demonstrating that nutrient-diversity feedbacks in multitrophic systems can stabilize ecosystems by balancing variability and extinction risks, independent of traditional portfolio effects.

Contribution

It presents a novel nutrient-diversity feedback mechanism in a food chain model, highlighting its stabilizing effects on ecosystems beyond portfolio theories.

Findings

Nutrient-diversity feedback increases community variability.

Higher phytoplankton diversity enhances ecosystem robustness.

Diversity reduces destabilizing over-growth effects.

Abstract

Statistical averaging and asynchronous population dynamics as portfolio mechanisms are considered as the most important processes with which biodiversity contributes to ecosystem stability. However, portfolio theories usually regard biodiversity as a fixed property, but overlook the dynamics of biodiversity altered by other ecosystem components. Here, we proposed a new mechanistic food chain model with nutrient-diversity feedback to investigate how dynamics of phytoplankton species diversity determines ecosystem stability. Our model focuses on nutrient, community biomass of phytoplankton and zooplankton, and phytoplankton species richness. The model assumes diversity effects of phytoplankton on trophic interaction strength along plankton food chain: phytoplankton diversity influences nutrient uptake by phytoplankton and zooplankton grazing on phytoplankton, which subsequently affects nutrient level and community biomass of phytoplankton and zooplankton. The nutrient level in turn affects phytoplankton diversity. These processes collectively form feedbacks between phytoplankton diversity and dynamics of plankton and nutrient. More importantly, nutrient-diversity feedback introduced additional temporal variabilities in community biomass, which apparently implies a destabilizing effect of phytoplankton diversity on ecosystem. However, the variabilities made ecosystems more robust against extinction of plankton because increasing phytoplankton diversity facilitates resource consumptions when consumers prone to extinct; while, reducing diversity weakens destabilizing dynamics caused by over-growth. Our results suggest the presence of a novel stabilizing effect of biodiversity acting through nutrient-diversity feedback, being independent of portfolio mechanisms.