中文摘要：

花期物候变化研究对赏花活动安排、园林景观布置和致敏花粉防治等具有重要意义。现有研究对始花期与盛花期的变化趋势已有较为深刻的认识,但很少有研究辨识了花期长度的时空变化。本文基于＂中国物候观测网＂观测数据,统计了1963-2012年中国42个站点23种广布木本植物的花期长度变化趋势,分析了花期长度变化的时空格局、种间差异和变化形式。主要结论为：所有的259条花期长度时间序列中,61.39%的序列呈延长趋势,其中显著延长的占21.24%（P〈0.05）。灌木花期的延长趋势比乔木更加显著。东北地区南部、华中和华东地区的多数站点花期长度主要呈缩短趋势。在东北地区北部、华北、西南和华南地区,大多数物种的花期长度呈延长趋势。花期长度变化趋势在20°N~22°N间最大（0.94 d/a）。西部地区（87°E~112°E）的花期长度变化趋势（平均0.28 d/a）高于东部地区（平均0.05 d/a）。花期长度的总体变化可分为3个阶段：1963-1980年（偏短）、1981-1997年（与多年平均值接近）和2001-2012年（偏长）,但不同物种的花期长度变化存在显著差异。在花期长度延长的序列中,43.39%是因开花始期提前程度大于开花末期;在花期长度缩短的序列中,62.00%是因开花始期提前程度小于开花末期。

英文摘要：

Flowering phenology is of great importance for flower tourism planning, landscape arrangement, and pollen allergy forecast. Previous studies mainly focused on the changes in the first flowering date of plants, but rarely examined the spatiotemporal changes in flowering duration. In this study, we systematically analyzed the changes in flowering durations for 23 woody plants at 42 sites from China Phenological Observation Network（CPON） during 1963-2012. Through investigations on the spatiotemporal patterns, interspecific difference, and the forms of change in flowering durations, the following conclusions are drawn.（1） Out of all the259- time series, flowering durations have lengthened in 159- time series（61.39%）, where21.24% have lengthened significantly. The extending trends for shrub species are found to be more significant than those for tree species.（2） Most flowering durations in the south of Northeast China, East China, and Central China exhibited trends of shortening, but those in the north of Northeast China, North China, parts of Southwest China, and South China exhibited extending trends. The strongest trend（0.94 d/a） occurred at around 20° N. The mean trend of flowering duration（0.28 d/a） in western China（87° E- 112° E） was larger than that in eastern China（0.05 d/a）.（3） The overall changes in flowering duration could be identified into three stages： 1963-1980（shorter）, 1981-1997（close to multi-year average） and 2001-2012（longer）,although evident difference existed among species.（4） As for the time series with extending flowering duration, 43.39% were induced by a much earlier first flowering date than the end of flowering date. For the time series with shortening flowering duration, 62% were caused by a more advanced trend at the end of flowering date than at the first flowering date.