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Abundance, biomass and density boundaries in the Hymenoptera : analysis of the abundance - weight relationship and differences between forest and open landscape habitats

Ulrich W.

Polish Journal of Ecology

1999

Vol. 47, no 1

73-86

The density - weight distributions of the hymenopteran species in a beech forest on limestone and a dry meadow on limestone near Gottingen (FRG) were studied. Species and density distributions (logarithmic size classes) turned out to follow normal and log-normal distributions with the meadow having the more narrow shape. Upper weight classes accumulated more total biomass m^-2 than lower ones, resulting in a rejection of the equal biomass hypothesis in the case of the Hymenoptera. An analysis of the density - weight relationship revealed an upper density boundary for the hymenopteran species which can be defined by second order polynomial functions. Mean and upper densities of small hymenopteran species ranged well below their boundaries, with an asymptotic relationship between distance from the boundary and species weight. The area defined by the boundaries may mark the area of stability: exceeding the species specific boundary was always followed by a marked decline oreven a collapse of population density.