The parasitic Hymenoptera in a beech forest on limestone. 3, The role of leaf litter for the parasitoid species

Ulrich, Werner

doi:ISSN 1505-2249

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Tytuł: The parasitic Hymenoptera in a beech forest on limestone. 3, The role of leaf litter for the parasitoid species

Abstrakt:

In a mixed beech forest growing on limestone, the effect of an enhanced and a reduced layer of leaf litter on the emergence of parasitic Hymenoptera (as well as their hosts) was studied. A long term increase (4 years with an initially 5-fold value) of the leaf layer and a short term experiment (1 year, factor 5) resulted in a rise of the total density of soil living parasitoids. The abundance of parasitoids which attack hosts in the herb layer or canopy declined. However, in both groups diversity and evenness was lowered. A reduction of the layer of leaf litter resulted in lower densities of the parasitoids of soil living hosts, but higher abundances of the parasitoids of hosts in other strata. The lacking leaf layer caused a reduction in the number of species and lowered both diversity and evenness. The lacking leaf layer also caused changes in the species composition. Experiments with dead snails to attract necrophagous insects and their parasitoids covered by different amounts of leaf litter revealed a species specific reaction to the leaf cover. Total parasitism rates were not reduced under a thick layer of leaf litter. No protective function of the leaf cover could be detected.

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