Main research in agroecology is on patterns and mechanisms of biodiversity and ecological functions in agricultural landscapes. This includes the relative importance of local and regional scales as well as bottom-up and top-down effects with respect to the regulation of population size in multitrophic food webs. Such basic ecology is related to the conservation and enhancement of beneficial interactions in agroecosystems.
The general topic is "Biodiversity and plant-insect interactions in fragmented landscapes" with the following specific topics:
- Interactions among plant-feeding insects and their natural enemies (parasitoids, predators) in agroecosystems (e.g., wheat, oilseed rape, legumes, tropical systems with cacao, coffee, grassland).
- Wild bees and honey bees as pollinators, fruit set, and seed predation of wild and cultivated plants (e.g., oilseed rape, legumes, coffee).
- Population dynamics of plantsi n dependence on herbivory and pathogen infections (e.g., Creeping Thistle, invasive plants, grasses).
- Multitrophic Interactions between plants, pathogens, phytophagous and entomophagous insects and insectivorous birds, between below- and aboveground processes, between plants (interplant signal transfer) and herbivores, between herbivory and pollination.
- GIS-based management of man-made landscapes, to enhance biodiversity and ecological functions (biological weed and pest control, pollination).
- Landscape complexity and habitat fragmentation as determinants of local processes and community structure (vegetation of arable fields, grasslands, and fallows, phytophagous and entomophagous insects, also butterflies).
- Land-use systems in the tropics (Indonesia, Ecuador, Madagascar) and temperate regions, their biodiversity in relation to biotic interactions and their importance for conservation.
The significance of the research topics for teaching is particularly evident with respect to the knowledge of species identifications (plants, insects), GIS-based landscapes analyses and geostatistics, relation of biodiversity and ecological functions, biological control of pests and the enhancement of beneficials, bee keeping, statistics and experimental designs, population genetics and plant chemistry, landscape management and nature conservation.
For example, effects of set aside, extensification of grasslands, and field margin strips on the species richness of flora and fauna are studied. These analyses do not only deal with biodiversity and the survival of endangered species, but also with the ecological effects of species loss. For example, the local extinction of natural enemies (predatory insects and parasitoids) affects the biological control of pest insects. Similarly, many bee species are endangered by the destruction or fragmentation of their habitats. Local extinction of these pollinators leads to reduced seed set of many wild and crop plants. Accordingly, possibilities to augment beneficials by alternative cultural practices are wanted. Two examples: (1) In a comparison of crop fields in structurally complex and simple landscapes, we found that simple landscapes (with high land-use intensities) led to reduced levels of mortality of rape pollen beetles (due to parasitism) and thereby, to enhanced rape damage. (2) In a comparison of agroforestry systems differing in shade and distance to forests, bee diversity differed greatly and could be related to fruit set of coffee.
General research perspectives
The relative importance of local and regional effects on biodiversity and ecological functions (habitat vs. landscape management).
The relation of biodiversity and ecological functions (predation, parasitism, pollination).
The comparison of tropical and temperate communities (phytophagous and entomophagous insects per plant, pollinators and trap-nesting bees and wasps).
The differences between agroecosystems and near-natural ecosystems (biodiversity, biotic interactions, biocontrol).
Multitrophic interactions (direct and indirect effects, below- and aboveground interactions, insect-pathogen and herbivore-pollinator interactions).