德国西部生长季节的一次趋势转折

近年的研究指出 ,北半球植被的生长季节正在逐渐延长。这一根据大气二氧化碳浓度季节变化、陆地年平均气温和卫星遥感数据的推断 ,尚有待于利用对地面植被的实际观测资料予以检验。由于植物物候现象如开花、展叶、叶变秋色和落叶等客观地描述了陆地植被的季节性生长状况 ,所以 ,利用树木的物候发生期便可确定生长季节的开始与结束时间。文中分析了德国西部 10个自然区域近 30年来物候生长季节长度的时间波动 ,发现在 2 0世纪 70年代中期存在着一次趋势转折 ,从而表明 ,有关近几十年来北半球高纬地区植被生长季节在逐渐延长的结论 ,并不能代表德国西部的实际情况。进一步的研究显示 ,生长季节时间序列与指示其开始的春季物候发生期时间序列呈负相关关系 ,而与 1月或 2月气温时间序列呈正相关关系 ,由此推断 ,春季物候发生期与气温的变化可以作为检测生长季节长度波动的早期征兆。

A TREND REVERSE OF GROWING SEASON IN THE WESTERN GERMANY

For recent years, the research has showed that there is a gradual lengthening of the growing season in the Northern Hemisphere. This inference based on the records of the seasonal signal in atmospheric CO 2, the surface air temperature and the satellite data have yet to be proved by field observation data of land vegetation. Because the plant phenological events, such as flowering, leaf unfolding, leaf coloration and leaf fall, etc, describe objectively the seasonal growth in land vegetation, their occurrence dates can be used to determine the beginning and ending dates of the growing season. This article analyzes the temporal variations in the length of the phenological growing season for last 30 years in 10 natural regions in the Western Germany and finds a trend reverse during the mid 1970s.This finding implicates that the evidence on the lengthening of the growing season in the northern high latitudes could not represent the real situation in the Western Germany. Further analyses show that the time series of the length of the growing season has a negative correlation with the time series of the occurrence date of the spring phenophase that indicates the beginning of the growing season, and a positive correlation with the time series of temperature in January or February. Therefore,the changes in spring phenology and temperature can be used as an earlier indication for detecting the fluctuations in the length of the growing season.