Phenological changes reflect climate change in Wisconsin

A phenological study of springtime events was made over a 61-year period at one site in southern Wisconsin. The records over this long period show tha t several phenological events have been increasing in earliness; we discuss evidence indicating that these changes reflect climate change. The mean of regressions for the 55 phenophases studied was -0.12 day per year, an over all increase in phenological earliness at this site during the period. Some phenophases have not increased in earliness, as would be expected for phen ophases that are regulated by photoperiod or by a physiological signal othe r than local temperature.