Response of Robinia Pseudoacacia First Leaf Date to temperature and Precipitation Change in China in the Past 50 Years

Plant phenology is a significant indicator of climate change. Climate change has affected plant phenology greatly over the past few decades in mid-high latitudes of the Northern Hemisphere. Previous studies mainly focus on the relationship between plant phenology and temperature, but few of them have evaluated plant response to other climate factors, e.g. precipitation. In order to explain how plant phenology responses to precipitation and compare the magnitude of the impacts of temperature and precipitation on plant phenology, long-term (1963-2012) observations of First Leaf Date (FLD) of Robinia pseudoacacia at 9 stations in China over the past 50 years were analyzed using linear regression and partial least squares (PLS) regression analysis. The results suggest that the years with more precipitation exhibit later Robinia pseudoacacia FLD in most stations except Xi'an and Haerbin, but the correlations are not significant. Compared to temperature, precipitation shows opposite and much lower effects on plant phenology. FLD of Robinia pseudoacacia correlated positively to the spring precipitation in the 2-3 months before the onset dates of FLD. Meanwhile, it is negatively associated with the winter precipitation of the former year. However, the exact dates when such relationship appears varies among different stations, ranging from the former October to February. In addition, precipitation has smaller effect on plant phenology in stations with more precipitation, especially in semi-humid regions.