Size (QMD: quadratic mean diameter)-density relationships for the studied plots (1993 and 2005) and for some subalpine, old-growth Norway spruce forest in central Europe. Solid dots represent the Valbona plots respectively in 1993 and in 2005. VB2a is currently above 80% of the SDI that represents the biological carrying capacity of the site. VB1 is very close to this threshold. Empty dots represents size-density pairs for central European old-growth stands (see Tab. V). The relative density in old-growth stands ranges between 35 and 60% (OGZ: old-growth zone) suggesting that old-growth stage processes occur after a reduction of competition intensity due to both autogenic and allogenic disturbances