The Impact Of Climate Change On Tree Phenology In Recent 50 Years In China

The study of the response of tree phenology to climate change is one of hot issues at present. Statistic methods were applied to investigate the impact of air temprature, precipitation and sunshine on tree phenology for the period of 1950-2000, and it was found out that air temperature is the main factor to significantly influence first-flowering phenology. Subsequently, the correlation between budding dates, flowering dates and growing season and average and accumulated air temperature were discussed.It is showed that air temperature influences first-flowering dates the most, sunshine does less and precipitation does the least. An increase in air temperature and sunshine hours leads to an advance of first-flowering dates while an increase in precipitation makes them delay. Air temperature in spring and late winter mainly influences first-flowering dates, and the higher the air temperature, the advancer the flowering dates. Air temperature in spring is characterized by average, maximal and minimal temperature, maximal temperature influences first-flowering dates the most, average temperature does less and minimal does the least. The observed trend of annual and ten-year fluctuation in flowering phenology corresponds well with air temperature in spring. In general, a deviation in temperature is bigger than that in phenology.The budding dates are mostly influenced by air temperature in winter, a warmer winter and late autumn leads to an earlier beginning of budding. The earlier species which spend longer time in budding are more sensitive to change in temperature than the latter which need shorter period to sprout, at the same time, a higher temperature in early spring leads to fewer days for the former and a higher minimal temperature in late autumn and early winter leads to more days for the latter to complete sprouting.Air temperature in early spring mostly influences growing seasons, and air temperature in late autumn does in a certain degree. An increase in air temperature in spring causes an advance of growing season, in late autumn and winter leads to a delay. Thus the length of growing season is relatively prolonged, and the former is a main reason.