Response of chestnut flowering in Beijing to photosythetically active radiation variation and change in recent fifty years

Abstract

Climate warming has affected plant phenology throughout the world,but few studies have evaluated plant phenology response to other climate factors( e. g. photosynthetically active radiation-PAR). In particular,the response of fruit flowering to PAR variation has not been explored yet. Long-term( 1963-2008) of chestnut( Castanea mollissima Blume) first flowering dates from Beijing,China were related with daily PAR for the 12 months,using Partial Least Squares( PLS) regression analysis. Two relevant phases were identified,during which mean PAR,temperature,and relative humidity( RH) were correlated with flowering dates,respectively.PAR during the both relevant periods decreased significantly in Beijing over the past 50 years. Reduced PAR during 24 September-5 February showed an advance impact on chestnut flowering,and could explain 12% of advance trend in flowering timing. Deceased PAR during 6 February-31 May had a delayed effect on tree flowering,butit was not significant enough to reject the null hypothesis of no impact over time. Advanced flowering of chestnut was mainly determined by increasing temperature between 6 February and 31 May which could explain 41% of flowering trend. Relative humidity variation during this period played secondly important role on tree flowering. Considering the interaction among these three climate factors,the impacts of PAR and RH on flowering timing could partially be attributed to the effects of temperature variation