Decreased Functional Diversity and Biological Pest Control in Conventional Compared to Organic Crop Fields

Organic farming is one of the most successful agri-environmental schemes, as humans benefit from high quality food, farmers from higher prices for their products and it often successfully protects biodiversity. However there is little knowledge if organic farming also increases ecosystem services like pest control. We assessed 30 triticale fields (15 organic vs. 15 conventional) and recorded vascular plants, pollinators, aphids and their predators. Further, five conventional fields which were treated with insecticides were compared with 10 non-treated conventional fields. Organic fields had five times higher plant species richness and about twenty times higher pollinator species richness compared to conventional fields. Abundance of pollinators was even more than one-hundred times higher on organic fields. In contrast, the abundance of cereal aphids was five times lower in organic fields, while predator abundances were three times higher and predator-prey ratios twenty times higher in organic fields, indicating a significantly higher potential for biological pest control in organic fields. Insecticide treatment in conventional fields had only a short-term effect on aphid densities while later in the season aphid abundances were even higher and predator abundances lower in treated compared to untreated conventional fields. Our data indicate that insecticide treatment kept aphid predators at low abundances throughout the season, thereby significantly reducing top-down control of aphid populations. Plant and pollinator species richness as well as predator abundances and predator-prey ratios were higher at field edges compared to field centres, highlighting the importance of field edges for ecosystem services. In conclusion organic farming increases biodiversity, including important functional groups like plants, pollinators and predators which enhance natural pest control. Preventative insecticide application in conventional fields has only short-term effects on aphid densities but long-term negative effects on biological pest control. Therefore conventional farmers should restrict insecticide applications to situations where thresholds for pest densities are reached

Phasenstabilitaet und Phasengleichgewichte in Gemischen aus Kohlenwasserstoffen, Alkoholen und Wasser

Vielstoffgemische aus Kohlenwasserstoffen, Alkoholen und Wasser sind -beispielsweise unter dem Gesichtspunkt alkoholhaltiger Vergaserkraftstoffe - von hohem praktischen Interesse. Hier sind exakte Beschreibungen der Fluessig-Fluessig-Stabilitaetsgrenze in Abhaengigkeit von Temperatur und Zusammensetzung sowie der sich bei eingetretener Phasentrennung einstellenden Fluessig-Fluessig-Gleichgewichte gefordert. Die in dieser Arbeit entwickelten Modellierungsmethoden fuer die Phasenstabilitaet komplexer Gemische aus Kohlenwasserstoffen, Alkoholen und Wasser sowie fuer die LL-Phasengleichgewichte solcher Gemische wurden in Computerprogramme umgesetzt, die - basierend auf einem umfangreichen experimentellen Material - komprimierte, vergegenstaendlichte Erfahrung darstellen. Diese Programme ermoeglichen eine solide rechnerische Abschaetzung eines Grossteils aller Probleme, die mit der Phasenstabilitaet methanolhaltiger Vergaserkraftstoffe zusammenhaengen. Darueber hinaus sind die Programmalgorithmen prinzipiell auch fuer die Behandlung anderer Stoffsysteme geeignet. (orig./BBR)Multicomponent mixtures of hydrocarbons, alcohols and water are of great practical import, for example in serving as alcoholic carburettor fuels. Such applications require an exact delineation of the liquid-liquid stability bounds as a function of temperature and composition as well as of the liquid-liquid equilibria that occur after phase separation. In this study the modelling methods developed for the phase stability of complex mixtures of hydrocarbons, alcohols and water and for the LL phase equilibria of such mixtures were transposed into computer programmes. Based on a large quantity of experimental data these programmes, then, constitute condensed, materialized experience. They permit a sound calculational estimation of the majority of problems relating to the phase stability of carburettor fuels containing methanol. Beyond this the programme algorithms are principally suitable for dealing with other chemical systems. (orig./BBR)SIGLEAvailable from TIB Hannover: H93B3146 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman