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Split-plot design
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We use a split-plot design to test for different treatment effects:
- Management ("U"/"M"): Silvicultural interventions may mask potential diversity effects because stands are kept at a constant density or basal area. One subplot will be without any management (labelled "U" for "unmanaged"). The other subplot will be thinned according to state-of-the-art management rules of close-to-nature forestry (labelled "M" for "managed").
- Additional species ("M+"): Because modern close-to-nature forestry aims to increase the tree species richness by promoting sub-dominant or minor species, we will add a third subplot where 4 additional species (see species pool) are included at each diversity level. This subplot will also be managed. The variant "unmanged plus additional species" will be ommitted due to limitations of space and because subdominants may be outcompeted by dominants without silvicultural intervention.
- Reduced genetic diversity ("M-"): At the site "Kaltenborn", another subplot at the 1-species level will be planted with clones or seedlings with low genetic variability in order to check for influences of genetic diversity on the performance of monoculture stands. These subplots will also be managed to ensure relevance for forestry. The clones will be produced in 2003/2004 and will thus be planted approximately three to four years later than the plants of the main plots.
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Plot size will be 1.02 ha (calcareous site) and 0.6 ha (acidic site). |
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