Relationships between forest floor vegetation on ICP Forests monitoring plots in Europe and basic variables in soil and nitrogen deposition

摘要

Forest floor vegetation is repeatedly assessed on intensive monitoring plots of the ICP Forests programme along with environmental parameters such as deposition and soil factors. Based on the floristic composition of the herb layer, detrended correspondence analyses (DCA) were performed. The first axis of a DCA based on 720 forest plots across Europe revealed a phytogeographic differentiation of the Mediterranean plots and may moreover partly reflect nationally deviating plot selection criteria. In a DCA with a reduced data set of 488 plots restricted to the nemoral zone of Europe the acidity status of the soil was the most decisive environmental factor. None of the available environmental factors was correlated with plot scores of the second and third DCA-axis. However, scores of the fourth axis were significantly correlated with plot specific throughfall deposition of total nitrogen (R~2 = 0.27). Nitrogen indicating species like Ceratocapnos clavicutata obtained high scores on that axis corroborating eutrophication effects of atmospheric nitrogen deposition on forest floor vegetation. The results of a DCA based on 97 plots with at least three repetitions in the years 1994-2003 did not reveal consistent temporal trends in plant species composition of the observed plots.