Effects of temperature, phase type and timing, location, and human density on plant phenological responses in Europe

Phenological onset dates are closely linked to temperature. In this study, we analysed a phenological dataset collected during the COST 725 Action 'Establishing a European phenological data platform for climatological applications', which contained more than 36 000 phenological time series for Europe covering 1971-2000. We analysed the temperature response of the phenological phases, their regional differences, and the relationship between the sizes of the local temperature and phenology trends in connection with a high-resolution climate grid of Europe. As an external factor, we examined the influence of human population density on phenology. Our analyses confirm differences in behaviour between annual and perennial plants in Europe. The average temperature response of perennial plants was significantly greater (-4.2 d °C^-1) than that of annual agricultural crops (-3.0 d °C^-1) The correlation between temperature and phenology trends was greatest for leaf unfolding of fruit trees and deciduous trees (r = -0.63 and -0.46, respectively). The geographic coordinates (latitude and longitude) had only a modest influence on the mean onset of the groups of phases; however, inclusion of altitude improved the models for some groups.