Forest lakes affected by forestry - how resilient are dragonfly communities to logging in Central Sweden?

Abstract: The main cause of environmental disturbance in the Fennoscandian boreal forests today is forestry. Natural disturbances are important to maintain diversity, but anthropogenic disturbance, such as forestry, differs in many ways from the natural ones. Forestry is a big industry in Sweden and only a small remnant of old-growth forest is left. Several studies have shown an initial decrease in e.g. dragonfly diversity a few years after logging, followed by an increase up to numbers comparable with the original species number. In this study I examined whether the new, quite diverse, species composition is similar to the one present before the logging or if some species are disappearing and are replaced with other, maybe opportunistic species. Other factors such as ongoing changes in climate also will be considered. A resampling of 34 (and an additional 4) lakes that also were sampled in 1996-97 was done during summer of 2006. Analyses of data from the two sampling occasions were done. I found that even if the diversity is just temporarily affected (or not affected at all), it is not always the same species involved. This means that the diversity in a single lake can appear to be high, but the total diversity in Sweden, or Scandinavia, is declining. I also found some interesting new species for the area, such as Nehalennia speciosa, Sympecma fusca and Aeshna mixta.