Hypothesized changes in beta diversity of stand structural elements, vascular plants, wood-inhabiting fungi and saproxylic beetles at three stages of bark beetle-induced forest succession. Mature: mature spruce forest, Initial ES: initial early-seral stage, Adv. ES: advanced early-seral stage. Beta diversity is defined here as among-plot heterogeneity of one successional stage on the landscape scale and can therefore be a measure of both structures and species.

On the Structural and Species Diversity Effects of Bark Beetle Disturbance in Forests During Initial and Advanced Early-Seral Stages at Different Scales

Abstract

Following disturbances, early-seral stages of forests provide a variety of structures. Whether this variety is a short-term phenomenon or influences forest succession for several decades or even longer is not known. We tested the hypotheses that after spruce dieback caused by bark beetles, a high spatial heterogeneity of stand structures will persist within stands and among stands even in advanced early-seral stages and that species taxonomical and functional diversity measures will reflect this heterogeneity. We used a chronosequence of unmanaged forests in the Berchtesgaden National Park (Germany) consisting of mature undisturbed spruce stands (control), stands belonging to an initial early- seral stage (3 years after disturbance) and stands in an advanced early-seral stage (20 years after disturbance). We analysed diversity and heterogeneity of these forest stands including stand structure, species density, species composition and functional–phylogenetic diversity of vas- cular plants, wood-inhabiting fungi and saproxylic beetles within plots, among plots of the same successional stage and among stages. Stands of the advanced early-seral stage were characterized by a high spatial heterogeneity of structural attributes, such as crown cover, regeneration density and spatial distribution of trees. Among-plot taxonomic beta diversity was highest in the advanced early-seral stage for beetles, but lowest for fungi, while beta diversity of plants among plots remained unchanged during succession. The mosaic of successional stages initiated by bark beetles increased the gamma diversity of the study area, especially for fungi and beetles. Our findings support the hypothesis that structural heterogeneity continues for at least two dec- ades at stand and landscape scales and that species turnover among successional stages is a major mechanism for gamma diversity in forests after bark beetle disturbance.

Publication
In European Journal of Forest Research, Eur J Forest Res.
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