Funktionelle Ökologie: Die Auswirkung unterschiedlicher Landnutzungsintensität auf die Diversität chemischer Pflanzenduftstoffe, strukturelle Komplexität der Vegetation und Wirt-Parasitoid Interaktionen

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Land use (LU) may affect plant and animal species diversity not only by reducing species numbers, but also in a functional way. We expect changes in the vegetation, apart from reducing species numbers of higher trophic levels, to also influence the function of biotic interactions. Results from the previous project phase suggest that LU, plant species diversity and host plant parameters are the most important variables to affect the occurrence of the Plantago lanceolata-inflorescence feeders and their parasitoids studied. Whereas LU intensity per se and experimental fertilization mostly showed a negative influence on the host-parasitoid system, plant species diversity and host plant abundance increased the occurrence probability of all interacting organisms. Volatile chemical diversity was plot specific, correlated with plant species diversity in the Exploratory Alb, and affected insect movement patterns. We aim to continue to investigate the influence of diversity of habitat odours and to examine experimentally the proximate and ultimate reasons for the previously observed distribution patterns of the flowerhead insects in relation to LU. We hypothesize that LU influences species occurrence and the function of biotic interactions: I) LU intensity alters, along with plant species diversity, the chemical diversity of the vegetation. II) Increasing odour diversity functionally influences herbivore-parasitoid interactions by reducing the host finding success of the parasitoids. III) LU type (grazing, mowing) influences insect occurrence by a) local adaptation of host plant populations or b) disrupting the phenologies of the species investigated. IV) LU intensity and experimental fertilization have a negative impact on flowerhead insects due to a negative effect a) on host plant abundance or b) on plant species richness and possibly plant odour diversity.