近五十年北京板栗始花物候对光合有效辐射变化的响应

与全球范围内气候变暖对植物物候影响研究相比，其他气候因素（如光合有效辐射PAR等）对物候影响报道较少，果树花期物候对光合有效辐射变化响应的研究更是未见报道。本研究以1963—2008年间北京板栗始花物候资料及相应的日光合有效辐射数据为基础，利用偏最小二乘回归法确定了PAR影响板栗始花物候的两个关键阶段，进而分析了两阶段内PAR、温度及相对湿度变化对板栗花期的具体影响。结果表明，北京过去50年两相关阶段内PAR呈显著下降趋势，其中9月24日至次年2月5日问PAR下降对板栗花期提前具有促进作用，可解释12％的花期提前趋势；2月6日至次年5月31日间PAR下降促使花期延迟，但未达显著水平（P〉0．1）。板栗花期提前主要与2月6日至次年5月31日间温度升高有关，其间温度变化可解释41％的花期提前趋势；其次是相对湿度，PAR变化对花期影响较小。鉴于PAR、温度及相对湿度间的互作效应，PAR和相对湿度对花期物候的影响可由温度效应加以解释。

Response of Chestnut Flowering Active Radiation Variation and in Beijing to Photosynthetically Change in Recent Fifty Years

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, but it 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.