Plant Phenological Reconstructions and Temperature Sensitivity in Beijing in the Past 100 Years

Plant phenology can reflect the climate change very sensitively. Reconstructing long-term phenological time series could contribute to the study of the climate-vegetation relationship from a historical perspective. However, previous studies have some problems in the interpolation method of missing data, the reconstruction method of time series as well as the uncertainty analysis. To overcome these problem, we use modern phenological observation data to calibrate the transfer functions between different phenophases and first flowering date (FFD) of lilac (Syringa oblata), and reconstructed the lilac FFD in Beijing over the past 100 years based on the historical records. Meanwhile, we assess the associated reconstruction uncertainty. In addition, the 30-year moving trend, temperature sensitivity and abrupt change in the reconstructed phenological time series are analyzed. The moving linear trend analysis suggests that the spring phenophase in Beijing fluctuated about 36 days in the past 100 years. The spring phenophase showed advancing trend in all the 30-year period after 1980. The maximum trend of -0.46 days/year is found between 1979 and 2009. However, the trends slowed down in the recent 10 years. The sensitivity of spring plant phenology to the March-May temperature ranged from 1.5 days /°C to 5.6 days /°C. Temperature sensitivities were greater during every 30-year periods with the center year from 1930s onwards. It is worth noting that after the 1980s, temperature sensitivities became continuous greater. Finally, the moving t-test showed a common shift towards earlier FFD in 1982 in temperature and plant phenological records.