Weed flora monitoring data from agricultural fields under conventional use in the AgroScapeLabs Quillow in Northeast Germany from 2000 to 2019 – here: species occurrence/frequency data

Systematic vegetation surveys were performed from 2000 to 2019 yearly within the “Quillow-AgroScapeLab”, located in the north-eastern part of the German lowlands (Figure 1). The area is 290 km2, the altitude ranges between 0–100 m above sea level. The landscape is of glacial origin and is characterised by a heterogeneous distribution of the following soil types: luvisols, arenosols, phaeozem, retisols, histosols, and planosols. The monitoring was varied out on in total 43 single agricultural fields, 23 out of them belong to the basic monitoring program at AgroScapeLabs Quillow (performed by ZALF) where other parameters have been monitored over time and 20 fields belonging to the Additional program, where only the weed monitoring has been performed. The fields of the Basic program have been selected based on a soil representativeness analysis based on soil map analyses in order to cover the most common and specific soil types within the whole Quillow (river) catchment. The additional program were set up in order to reach a better spatial cover over the whole catchment and to increase the field number. For each field a soil profile description is available from ZALF data repository. Management data are only available from 2000-2006. From later years at least the crop type is available. At each field there was a subunit of 0,5-1 ha selected around the fix plots as analyzed within the Twindataset (BK-VA-AgroScapelabsQuillow) (figure 2). Surveys were repeated every year at nearly the same places. Not every field could be monitored every year due to some restrictions by the field owners. From 2019 on winter rape fields were not be monitored anymore due to monitoring overlap with plant protection measures. Vegetation surveys were carried out on a subunit of 0,5 -1 ha size, including the plots for the exact estimation from the Twindataset. The field subunits of between 0.5-1 ha were mapped and assessments of each species´ frequency of occurrence were done. The classification of frequency was based on the following scale, including their intermediate values: mf – most frequent (occurring on at least 50 % of the field), f – frequent (occurring on at least 25 % of the field), sc – scattered/diffuse (occurring on at least 10 % of the field), r – rare/infrequent (only for a few species), mr – most rare (not more than 1-3 individuals on the field). Plants that could not be clearly identified were sampled and re-identified in the laboratory. By adding the data into a databank, species names have to be corrected to the nomenclature of Wisskirchen and Häupler 1998. Vegetation surveys have been carried out after herbicide treatments (if there were any) mostly between end of april, may, and june. (see data tables!). The number of survey dates per years was 1-2. It varies over the years and crops. Please note: a separate Twindataset (https://doi.org/10.4228/zalf-96p3-5n09) is available from the same study area and from the same fields, which contains information on fixplot related vegetation surveys on the arable land using a different method (species coverage estimation according to Braun-Blanquet) from a different survey area size (3x 25m²).