Ecological networks
Prof. Dr. Nico Blüthgen

How do ecosystems work, and why is biodiversity important for ecosystem functioning? Ecosystems are characterized by numerous players (species, individuals) interacting in complex ways (ecological interaction networks). Such interactions are the basis for ecosystem processes (nutrient cycling, biomass production, etc.) and ultimately for the benefits of nature to humans.

Species and networks

To understand mechanisms of interaction networks, we are using a combination of empirical field observations, experiments, ecophysiological measurements, functional traits and modelling, but also chemical analyses (signals, defensive compounds and nutrients). We develop conceptual tools and metrics for network analysis. We compare a broad spectrum of systems, including plant-pollinator, plant-herbivore, host-parasitoid and dung-beetle networks, as well as associations between nestmates or different species of social insects. Our studies relate natural and disturbed ecosystems in central Europe but also in tropical rainforests where biodiversity is particularly striking.

Mechanisms and consequences

We aim to understand why certain pairs of species interact while others do not (resource partitioning). What are the benefits and costs of being a specialist? Why are consumers specialised on certain resources – because of nutrition, chemical signals or other constraints? Does specialisation enhance the functional performance of the target system (functional complementarity), but represent an extinction risk? In turn, does biodiversity buffer the system against environmental disturbances (response diversity, functional redundancy)? The structure of ecological networks has important consequences for ecosystem processes and their stability. We particularly investigate how land-use intensity affects species communities, interactions and ecosystem processes, and how forest recovery can lead to re-assembly of species interactions.

Managing natural systems for biodiversity

A high diversity of interactions between species of different trophic levels (plants, herbivores, predators and decomposers) is crucial for high biodiversity in general (diversity of genes, species and ecosystems). The way humans interact with and manage ecosystems and habitats has a strong influence on this biodiversity and the interactions between species. By understanding how management decisions (especially in grasslands and forests) affect biodiversity and their interaction networks, we can help managers and users of natural systems to find and implement management regimes which benefit biodiversity. In order to improve the communication of scientific knowledge to stakeholders and the communication of management decisions to the public, we work together with social scientists and local stakeholders in inter-/and transdisciplinary projects.

Impressions of ongoing project in tropical rainforest in Ecuador