The BernClim plant phenological data set from the Canton of Bern (Switzerland) 1970-2018

In 1970, the Geographical Institute of the University of Berne initiated the phenological observation network BernClim. Seasonality information from plants, fog and snow originally served for applications in urban and regional planning, agricultural and touristic suitability and are now a valuable data set for climate change impacts studies. Covering the growing season volunteer observers record key development stages of hazel (Coryllus avellana), dandelion (Taraxacum officinale), apple tree (Pyrus malus) and beech (Fagus sylvatica). All observations consist of detailed site information including location, altitude, exposition and inclination that make BernClim unique in detail-richness and temporal coverage. Quality control by experts and statistical analyses system of the data has been performed to flag impossible dates, outliers of the biological range, repeated dates in the same year, four consecutive identical dates after removing non-first and dates outside of +/-3 sd of each series and all series for a given years after removing non-first. Here, we report BernClim data of 7414 plant phenological observations from 1970 to 2018 from 1304 sites at 110 stations, the quality control procedure and selected applications. QC points to a good internal consistency and likely a quality of the data. Variability tests flagged five dates (0.07%) were outside 3 sd per series and ten dates (0.13%) were outside 3 sd of all series in a given year. BernClim data indicate a trend towards an extended growing season. They also well track the regime shift in the late 1980s.