It is a therma sensitive stage on spring phenophase. (4) The temporal variation curve of spring phenophase in Beijing shows that at present spring phenophase in Beijing appears earlier.

• (4)近50年来，北京春季物候经历了3个周期的早晚振荡，近十几年来北京春季物候持续偏早，特别是近10年，其偏早天数创历史记录，这与北京近年持续的暖冬相一致。