Peak flowering responses to the global warming of woody species in Heilongjiang Province,northeastern China.

Phenological observations can provide a sensitive bio-indicator of temperature change. Flowering is an important phenophase and the start of plant reproduction, the shift of peak flowering is a core property of the series phenological variations. Northeast China locates on the sensitive zone of northern high latitude, many local species have significant phenological responses to global warming and are more representative. Based on the data sets of peak flowering observation and monthly average temperature during the past 52 years in Forest Botany Garden of Heilongjiang Province of northeastern China, we analyzed the peak flowering responses to the raising temperature of 50 woody species. Also the response difference of morphological function groups (tree or shrub) and the fruit types (fleshy or non-fleshy fruits) was explored. Results showed that the warming trend of study site was remarkable during the past 52 years. The rising ranges of mean annual temperature and mean springtime both reached 0.49 ℃ per 10 years, and significantly exceeded the average of global and nationwide levels; in 50 species, the peak flowering time of 38 species (76%) has significant correlation with the average temperature of April or May; peak flowering time showed advanced responses to the climate warming, averagely 2.09 days/℃ ahead, but there was obvious species-specific in advance rate. And the other 12 species(24%) did not have significant responses or were uncorrelated to the temperature warming. Varied species have difference in the response of peak flowering time to the mean temperature variation during the months of springtime. 34 earlier flowering species were highly significantly (P0.000 1, P0.01) or significantly (P0.05) correlated with the mean temperature of April, 4 relatively late flowering species were significantly (P0.05) correlated with the mean temperature of May; The above mentioned species which emerged advanced responses in peak time didn’t resemble each other in their phenological sensitivity on the morphological function group (tree or shrub) and the fruit type (fleshy or non-fleshy fruits) levels. The above results reveal the response characteristics of woody plants in peak flowering time to climate warming in northeastern China, and the results are basically identical to the relevant studies in Europe and North America and corroborate mutually. It could be a good foundation for the further studies.