Experimental research addressing the effect of biodiversity on ecosystem functioning (B-EF) traditionally focused on static plant communities with standing stock biomass as the ecosystem function. Theory in B-EF science yet was focused on simple mathematical descriptions mainly ignoring dynamics in multi-trophic communities, whereas modelling approaches of multi-trophic communities previously focused on stability and diversity while mostly ignoring functioning. Previous modelling approaches either examined the dynamics of complex communities with respect to only stable conditions or considered rather simplistic food-web motifs to investigate effects of ecological noise on the dynamics of a few species. Moreover, neither experimental approaches nor theoretical approaches investigating B-EF paid much attention to dynamically disturbed systems that may lead to changes in B-EF relationships.
The question how the functioning of complex multi-tropic communities react to different disturbance scenarios and biodiversity levels is crucial to understand B-EF in nature. Here we investigate how biodiversity and disturbances interactively change ecosystem functions such as respiration and gross primary production (GPP).
We used a multi-trophic dynamic bioenergetic model based on empirically estimated population parameters to simulate a community when exposed to a gradient of disturbance scenarios that differ in frequency and magnitude and measured dependent changes in functioning. Our model approach extends recent B-EF theory by providing an empirically based model framework that allows for predictions how disturbance changes (I) biodiversity and (II) ecosystem functioning. Moreover, our study represents a consequent development extending previous food-web models with complex communities to dynamics affected by stochastically changing conditions.
Results/Conclusions
We found that increasing frequency of disturbances decreased both, GPP and ecosystem respiration. Ecosystem respiration decreased stronger than GPP, indicating a higher rate of carbon binding with increasing number of disturbances. Contrasting, increasing strength of disturbances increased both, ecosystem respiration and GPP. Here, respiration increased more than GPP indicating an increase in CO2 release with increasing strength of disturbances.
Our modelling approach offered new insights and perspectives into changing ecosystem functioning in complex communities in response to disturbances. Such insights are crucial to understand consequences of extreme events caused by global change.