Arthropod dynamics on sagebrush (Artemisia tridentata): effects of plant chemistry and avian predation

摘要: We conducted a field experiment to assess interrelationships between leaf- tissue secondary chemistry, avian predation, and the abundance diversity of arthropods occurring on sagebrush (Artemisia tridentata) in central Oregon. Arthropods were removed from individual shrubs, some which then caged exclude birds. Secondary chem- istry sampled at intervals up 56 wk following defaunation/ caging treatment. Recovery rates differed among arthropod taxa functional groups. Several sap- sucking homopterans hemipterans reached control levels within 2-4 treat- ment, whereas abundances ofparasitoids predators recovered match numbers only 6 after defaunation. Abundances several herbivorous leaf-chewing (pri- marily lepidopteran larvae) remained significantly depressed even Fungivores (oribatid mites) greater defaunated than shrubs by end experiment. There also significant changes concen- trations or frequency occurrence chemical compounds defauna- tion hydrocarbons, sesquiterpenes, monoterpenes that present most exhibited sharply reduced concentrations leaf tissues 4 treatment, alcohols ketones (linalool, borneol, thujone), occurred relatively low frequencies plants, increased dramatically their fre- quencies removal. Both persisted for du- ration found associations groups compounds, but these prevalent lepidopterans. suggest responded removal herbivorous, altering allocation patterns; chemistry over year because recolonization plants herbivores was slow. Effects treatment much less obvious. The recovery known constitute prey birds this system slower