This dataset provides information about the study design, topography, geographic location and climatic conditions of the research plots of the interdisciplinary research training group 'RTG2300: Enrichment of European beech forests with conifers'. In each of forty forest stands, plots of 0.25 ha in size (called regular measurement plots, RMPs) were established in fall 2017 across the federal state of Lower Saxony, northwest Germany. The plots are grouped in eight so-called 'quintets'. Each quintet comprises five plots representing different forest stand types: three pure plots (European beech (Fagus sylvatica), Douglas-fir (Pseudotsuga menziesii), Norway spruce (Picea abies)) and two beech-conifer mixtures (beech-Douglas-fir and beech-Norway spruce). Four of the eight quintets are located in the southern part of the study area in the Solling and Harz mountain ranges. The other four quintets are located in the northern part of the study area in the North German plain. The southern plots are located in higher altitudes with lower mean annual temperatures and a higher annual precipitation. Growing conditions on the northern plots are less favorable than on the southern sites, in particular with respect to precipitation. On a subset of twenty out of the forty plots, intensive surveys such as root growth measurements, nitrogen retention analyses, or experiments on regeneration dynamics are carried out, besides the regular measurements on all plots. These intensive measurement plots (IMPs) comprise two southern and two northern quintets. Permanent, highly intensive measurements are conducted on special measurement plots (SMPs) that are a subset of 10 out of the 20 IMPs.

Annual averages of precipitation (column Precip) and air termperature (column Temp) are based on interpolations of weathers stations of the German Weather Service (DWD) (https://opendata.dwd.de/). Elevation of the plots has been included in the predictions.This dataset provides data about all research plots that were established between October 2017 and September 2020. Seven of the plots were affected by windthrow and had to be replaced at the beginning of 2018. This dataset contains information about abandoned and active plots (47 plots in total). The id of the plot is a combination of two digits that specify quintet (1 to 8) and mixture type (1: pure Douglas-fir (Pseudotsuga menziesii MIRB. FRANCO); 3: pure European beech (Fagus sylvatica L.); 5: pure Norway spruce (Picea abies L. KARST); 2: beech/Douglas-fir mixture; 4: beech/spruce mixture). For example, the pure spruce stand in quintet 3 is specified by the id '3.5'. Additionally, an optional letter is added to the ID to uniquely identify replaced plots. For example, plot '3.5a' specifies the initial research plot that was established at the end of 2017. '3.5' specifies the replacement of plot '3.5a' after all trees on the plot were thrown by a storm beginning of 2018. More plots are expected to be replaced in the future due to disturbance by windthrow or sanitary cuttings after bark beetle infestation. New datasets about these plots will be added to the collection whenever plots are being replaced.Only approximate locations of the research plots are specified. Acknowledgements:The RTG2300 is funded by the German Research Foundation (Deutsche Forschungsgemeinschaft – DFG). We would like to thank Johannes Sutmöller for providing interpolations of climatic variables for the last decades at plot locations from data of the German Weather Service (DWD).