1. Dep. of Agriculture and Ecology, Faculty of Life Sciences; Univ. of Copenhagen; Thorvaldsensvej 40 1871 Frederiksberg C Denmark
2. Dep. of Basic Sciences, Faculty of Life Sciences; Univ. of Copenhagen; Thorvaldsensvej 40 1871 Frederiksberg C Denmark
3. Ingenieurgesellschaft Prof. Dr. Sieker mbH, Rennbahnallee 109A 15366 Hoppegarten Germany
4. Center for Forest and Landscape, Faculty of Life Sciences; Univ. of Copenhagen; Rolighedsvej 23 1958 Frederiksberg C Denmark