Distribution of Damaged Oaks and Annual Oak Biomass Removal by Oak Nut Weevil(Mechoris ursulus) in Korea

다국어 초록 (Multilingual Abstract)

Herbivory is an important selective forces on plants by reducing the ability of the plant to compete with its neighbors and to produce offspring. Oak nut weevil (Mechoris ursulus Roelofs) females lay eggs in unmatured acoms and cut off the branch of oviposited acoms. To investigate the influences of branch-cutting behavior of oak nut weevils on oak production, we surveyed the horizontal and vertical distribution ranges of damaged oaks and depth of sites of overwintering larvae and quantified the amounts of biomass and acom removed by the weevils on deciduous oak species. All of the endemic oak species in Korea were damaged by oak nut weevils in all of the study sites including Mt. Halla and Mt. Seorak. The upper limit of vertical distribution of damaged oak by the weevils raried from 700m to 900. Mostly their larvae were found in soil from 8.1㎝ to 10.0㎝ depth in winter. Percentaged of annual net primary productivity(720g·m^-2·yr^1) of oak species removed by the weevils was about 7%, which is higher than the percentage removed by all the herbivores in typical temperate forest(5%) and equivalent to that by all the herbivores in tropical forest. The predation percentage of annual acom production by oak nut weevil was 27% in Q. mongolica and 33% in Q. acutissima. This results indicate that the branch-cutting behavior of oak nut weevil may be the most important factor regulating oak population and affecting other predators dependent on acoms.