1982~1999 年我国东部暖温带植被 生长季节的时空变化

利用1982~1996 年5 个站点的植物群落物候观测数据和物候累积频率拟合法, 划分各站逐年的植被物候季节, 并确定各季节初日对应的当地归一化差值植被指数(NDVI) 阈值。 在此基础上, 通过对物候站各年NDVI 曲线的年型聚类分析和区内所有像元逐年NDVI 曲线的空间聚类分析, 实现植被物候季节的时空外推估计, 从而得到我国暖温带落叶阔叶林地区1982~1999 年植被物候季节初日和生长季节长度的时空格局。结果表明, 多年平均的植被物 候季节初日和生长季节长度呈现出主要随纬度和海拔高度变化的空间格局。在这18 年中, 整 个区域的物候春季初日以提前为主, 且以华北平原提前的趋势最为显著；夏季、秋季和冬季 初日以推迟为主, 也以华北平原推迟的趋势比较显著；因此, 华北平原植被生长季节呈显著 延长的趋势。本文揭示的植被物候季节初日的趋势变化与华北地区各季节气温的趋势变化基本吻合；植被生长季节的趋势变化特征与欧洲单种植物物候生长季节, 以及欧亚大陆和我国温带遥感植被生长季节的趋势变化基本一致, 但植被生长季节初、终日期和长度的趋势值明显大于后者, 表明该地区植物物候对于气候变暖的响应更加敏感。

Spatial and Temporal Variations of the Vegetation Growing Season in Warm-temper ate Eastern China during 1982 to 1999

Phenological observation data of plant communities from 1982 to 1996 at 5 sites and a method for phenological cumulative frequency modeling were used to determine the beginning dates of local phenological seasons and their corresponding threshold values of normalized difference vegetation index(NDVI) in each year.Then,a year-type cluster analysis of NDVI profiles at each phenological station during 1982 to 1999 and a spatial cluster analysis of NDVI profiles for all of the pixels within the study area year by year were employed to fulfill a spatial-temporal extrapolation of vegetation phenological seasons.Consequently,we obtained spatial-temporal patterns of the beginning date of vegetation phenological seasons and the length of the vegetation growing season in the deciduous broad-leaved forest area of warm-temperate eastern China from 1982 to 1999.The results show that(1) the annual mean beginning dates of vegetation phenological seasons and the mean lengths of the vegetation growing season indicate changes of a spatial pattern mainly following latitude and altitude;(2) the beginning dates of the phenological spring dominate a significantly advanced trend over the entire area during 1982 to 1999,especially in North China Plain,whereas the beginning dates of the phenological summer,autumn and winter dominate a significantly delayed trend,also mainly in North China Plain,which causes a significant lengthening of the vegetation growing season in North China Plain;(3) linear trends of the beginning dates of vegetation phenological seasons are consistent with linear trends of seasonal air temperatures in North China;(4) the vegetation growing season lengthening revealed by the current study is consistent with the phenological growing season lengthening of the individual tree species in Europe,and the satellite-derived growing season lengthening in Eurasia and temperate China.