Development dynamics of Ichneumondiae (Hymenoptera) communities of Pinus sylverstris L. canopies in fresh pine forest in the three health zones of Poland's forests

Warsaw

1999

152 S.

Serie

83-87660-97-3

400062517

In the paper described are the Pinus sylvestris L. canopies Ichneumonidae communities in the four stages of secondary succession: the culture, the thicket, the premature stand and the mature stand, at the site of fresh pine forest, as studied in the three health zones of Poland's forests. The zones are represented by the three study regions: Bory Tucholskie Forest (Zone 1 of the poorest health status of forest - the largest degree of threat from the side of Scots pine primary insect invaders), Puszcza Biala Forest (Zone 2 - moderate risk) and Bialowieza Primeval Forest (Zone 3 - the least degree threat). With decreasing impact of pests, decreases also the man's impact and improves the richness of the accompanying plant vommunities. A total of more than 1,100 Ichneumonidae species were found, belonging to 23 subfamilies. The comminities were characterized using a number of parameters: abundance, species composition and dominance structure as well as the parasitoid-host relationships between particular species. In the case of Ichneumoninae subfamily, analyzed were also the following indices: species diversity, coenotic diversity, eveness, niche width and habitats overlap and the indices of communities complexity. The communities were compared by studying similarities and differences in their species composition and dominance structure. The studied re-creative succession was connected with the rise-and-fall succession type, with both the number of species and the values of indices of species diversity and communities complexity were clearly growing between the stage of culture - thicket, and then an opposite trend was observed with the stands maturation so that at the final (climax) stage of succession all the indices reached similar values regardless the region. The thicket communities' structural parameters were of intermediate character between the culture ones' and those of the older stands. Pine thickets play the role of ecotone in the landscape of clear-cut managed coniferous forest (pine monoculture). Some differences were noted in the course of succession that could be ascribed to the regional differentiation: along the west-east direction growing was the number of species, as well as the species diversity, the eveness, the mean habitat overlap and the complexity of the communities. The ichneumonidae communities became stabilized at the stage of about 50 years old forest stands: in those stands the most basic group of species were those parasitoids of pine Microlepidoptera. The nalyses of trophic relationships of the noted Ichneumonidae allowed for the identification of 13 trophic complexes of varying importance during the consecutive stages of succession. Regional differences were rather slight and they resulted from the massive occurrence of some hosts.