利用遥感监测长江三角洲森林植被物候对气候变化的响应

植物的物候与气候等环境因素息息相关,是指示气候与自然环境变化对生态影响的重要指标。目前,气候变暖日益为人所关注,使用遥感技术研究植物物候与气候变化之间的关系具有重要的意义。监测人口密度高和城市经济发达地区的植物物候对气候变暖的响应,可以揭示区域热环境变化及其产生的生态效应。本研究选取长江三角洲地区为研究区域,使用SPOT卫星VGT传感器的长时间NDVI数据序列,对经济发达区域森林植被的NDVI序列进行非对称性高斯函数拟合法平滑处理,并提取与研究其物候特征,发现①NDVI与气温具有较强相关性,随气候变暖,森林植被NDVI年均值有增加趋势;②森林植被生长活跃期起始日期提前,终止日期延后,时长有明显的延长趋势,生长活跃期内NDVI有所增加;③森林植被NDVI极大值与极小值出现日期均明显提前,NDVI极大值有增大趋势,而极小值呈下降趋势,年内极差增加,NDVI增长期缩短,衰落期延长;④森林植被在春、夏两季NDVI均值有所增长,秋季无明显变化,冬季略有降低。

Monitoring the Respond of Forest Vegetation Phenology to the Climate Changing in Yangtze Delta Region Using Remote Sensing

The vegetation phenological changes are closely linked with the ecological process and agriculture,forestry and environmental changes.Recently,the phenological responding to climate changing has been becoming a new hot research point.These studies showed that vegetation index（VI） could indicate the characters of each phenophase,and most of them were conducted by remote sensing technique.To reveal the effects of global warming on the biological phenomena in the high-density populated and economically developed regions,inter-annual and seasonal variability of NDVI for phenological characteristics of forest in the Yangtze delta region and its correlations with climatic variables are analyzed for the time period 1998-2008,using a dataset of 10-days averaged SPOT/VGT NDVI and local climatic data.A smoothing algorithm based on an asymmetric Gaussian function was firstly applied to the NDVI dataset to minimize the effects of anomalous values caused by atmospheric haze and cloud contamination.The result showed that（1） either in multi-year average or in each year,the variations of seasonal phenology and those of temperatures were synchronous,and the latter stably drove the former.The NDVI of forest has an increasing trend with the global warming from 1998 to 2008.（2） Forest had an earlier start of active growing season,later end of active growing season,longer active growing season and larger NDVI in the active growing season,with the time going.（3） For forest,an advancing of the time of maximum NDVI and a delaying of time of minimum NDVI are obvious.The maximum NDVI value had an increasing trend while the minimum NDVI value decreased,the difference of maximal and minimal NDVI in a year became larger,and the NDVI of forest had a shorter growing season but a longer senescence season.（4）The NDVI value of forest increased both in spring and summer,decreased in winter,and there is no significant change in the autumn.