Spatial and temporal patterns of Ellenberg nutrient values in forests of Germany and adjacent regions - a survey based on phytosociological databases

摘要: Within the last 30 years role of nitrogen in Central European forests has changed fundamentally from limiting resource to environmental problem. As retrospective tracking nutrient availability by soil chemical and biogeochemical measurements faces serious problems, bioindication based on understorey species composition is indispensable for monitoring broad-scale eutrophication. Based on a broad survey more than 100,000 forest vegetation plots accessible electronic data-bases Germany and adjacent countries, we calculated unweighted average Ellenberg nutrient values (mN) as proxy plant-available macronutrients. quantiles frequency distribution mN a regionally stratified sample, define five trophic classes, which can be used compare dimensionless values. We studied spatial patterns values within 17 regions compared periods 1899 1975 1976 to 2006. After eutrophic (mN > 5.67) hypertrophic > 6.28) conditions were common everywhere except Alps and Saxony-Anhalt, but very oligotrophic < 3.44) were still widespread regions with nutrient-poor bedrock. Before plots had been lower after all but southeastern regions. Between pre- post-1975 data proportion increased 5.7 to 11.8%, that oligo-trophic decreased 14.6 to 8.3%. To remove bias resulting uneven distribution, the dataset was tree layer dom-inance types, period region resampled. In pre-1975 medians of mN order Pinus sylvestris, Quercus spp., Picea abies, Fagus sylvatica Alnus spp, whereas increase highest types historically low nutrient values. Therefore, change must be attributed pronounced changes and Pinus stands, indicating importance land-use change, i.e. recovery cycles hundreds of exploita-tion through coppicing, grazing litter use. The analysis confirms eutrophication megatrend modern vegetation demonstrates high research potential of linking plot databases across large