Spatial and temporal changes of spring temperature, thermal growing season and spring phenology in Germany 1951–2015

Climate change has a strong impact on vegetation dynamics and the relationship between temperature changes and shifts in plant development is well known. However, temperature does not change homogeneously and high spatial and temporal variabilities are possible. For a 65-year period from 1951–2015, we examined trends of mean air temperatures and bioclimatic parameters such as the onset of thermal growing season and two relevant phenological stages in Germany. We focused our analysis only on statistical significant trends. In order to compare them for the same spatial and temporal resolution, gridded datasets were used. From 1951–2015 spring air temperature (March-May) increased by 1.9 K. In the same time the average onset of thermal growing season started 20 days earlier and the beginning of cherry flowering and leaf unfolding of silver birch was advanced by 11 and 13 days, respectively. Nevertheless, a high spatial variability of trends was detected for all parameters. Strongest shifts were more pronounced in coastal areas of Germany and the regional investigation showed significantly stronger trends for North Germany than for South Germany. The study confirmed a strong synchronisation of the temporal and spatial changes in air temperature and the investigated bioclimatic parameters.