70 Years of permanent plot research in The Netherlands

Within the framework of the Dutch `Network Ecological Monitoring¿, a large set of new permanent plots has been established to monitor selected plant communities throughout The Netherlands for studying the effects of environmental changes on species composition of semi-natural communities. This national programme will also make use of pre-existing permanent plots. These plots reflect the long and comprehensive history of research using permanent plots in The Netherlands, where the first permanent plots were established in the early 1930s. To enhance the usefulness of pre-existing permanent plots, a comprehensive permanent plot database was compiled. This database was derived from the Dutch National Vegetation Database, that was established for the recent vegetation classification of The Netherlands. This was supplemented with information from various organizations and a number of individual researchers. Currently, the permanent plot database contains ca. 6000 permanent plots. More than 2500 of these plots have been sampled at least 5 ×, and ca. 1500 plots at least 10 ×. Most of the plots are from grasslands, followed by forests and dune systems. This database not only provides insight into vegetation succession, fluctuations within plant communities over time, and the effects of changes of the environment on the vegetation but, indirectly, it also offers the possibility of studying the long-term behaviour of individual plant species (e.g. establishment, competition, longevity). For the Network Ecological Monitoring a selection of these (historical) plots will be added to the new network of permanent plots in The Netherlands, thus supplying information of past vegetation condition