Effekte von Waldumbaumaßnahmen in Kiefernforsten auf potenzielle Schädlingsantagonisten

Alfeld

2005

S. 287-290

2 Abb., 26 Lit. Ang.

Artikel aus einer ZeitschriftUnselbständiges Werk

200124699

In the northwestern Saxon lowlands effects of conversion of pure pine stands and the tolerance of multi-layered natural regeneration were investigated on predators and parasitoid wasps. Because of regional differences in the susceptibility of pine stands against mass gradations of pest insects pure pine stands of a typical gradation area and a latency area were included in the design of study sites. The effects of planting deciduous trees in pine stands were investigated by the strategy of "space-for-time substitution" including advanced plantations of beech and oak, differing in the age-class. A pine stand with natural regeneration was used to study the influence of an increase in vertical structure. Comparing the pure pine stands of the latency and gradation area, clear differences in the structure of the predatory guild were observed. Thus, predatory arthropods reached partly significant higher density levels in the latency area than in the gradation area. In terms of biomass the community of soil dwelling predatory arthropods was dominated by carabids in the pure pine stand of the latency area, by spiders in the pure pine stand of the gradation area. Contrary to the soil dwelling predator community, spiders were always the most important predatory pest antagonists in the canopy. In both areas advanced plantings of deciduous trees resulted in the long run in a strong promotion of the dominant predatory arthropod group living on the soil surface (ground beetles in the latency area, spiders in the gradation area). The strongest effects were manifested for oak. Comparable effects - but on a lower level - resulted from the tolerance of the natural pine regeneration. Comparing the pure pine stands of the latency and gradation area, individual numbers of most families of parasitoid wasps, developing in soil dwelling hosts were lower in the pine monoculture of the gradation area, though differences were not statistically significant. Advanced plantings of deciduous trees resulted in an increase of individual numbers of parasitoid wasps. Effects were evident especially in the canopy. To a lesser extent a promotion of parasitic wasps was also obtained by tolerating natural regeneration in pure pine stands resulting in an increase in vertical structure.