基于NOAA NDVI和MSAVI研究中国北方植被生长季变化

The variability of vegetation growing season in the northern China based on NOAA NDVI and MSAVI from 1982 to 1999

利用1982～1999年的NOAA／AVHRRNDVI和MSAVI指数监测了中国北方植被生长季变化规律，主要内容包括：（1）不同植被类型的生长季变化监测。提取植被的1982～1999年NDVI和MSAVI时间序列，利用阈值法和滑动平均法逐年估测植被类型的生长季的开始、结束日期及长度。对估测的生长季开始、结束时间和长度进行一次线性拟合，得到了18a中植被生长季的开始、结束日期和长度的线性变化趋势；（2）不同区域的植被生长季变化监测。将中国北方13省、区按纬向划分为32～36°N，36～40°N，40～44°N，44～48°N，48-52°N等5个区域。基于最大变化斜率法估测了不同年份的生长季开始、结束和长度；（3）研究区域植被生长季的空间变化监测。利用曲线拟合出1982～1999年像元对应的空间位置的植被平均生长季变化，然后讨论了多年平均的植被生长季的空间分异规律，并利用一次线性拟合分析了这18a的植被生长季的变化趋势。结果表明：部分植被类型生长季的开始日期提前，结束日期推迟，而生长季长度延长，提前或推迟的天数不一，如典型草原、荒漠草原、寒温带山地落叶针叶林。而一些植被类型的生长季并没有表现出这样的趋势，而是开始日期延迟或结束日期推迟，如温带落叶阔叶林。不同纬度带的植被生长季变化监测表明，大部分纬度带植被生长季开始日期都表现出不同程度的提前趋势，生长季结束日期表现出推迟的趋势，整个生长季长度表现出延长的趋势。中国北方植被生长季空间变化研究表明，青海、甘肃、陕南地区的植被生长季开始较早。新疆天山、东北北部、青海、甘肃的部分地区植被生长季结束较早。东北、青海、新疆的大部分地区的植被生长季有明显的延长趋势，整个研究区内有一部分地区的植被生长季长度表现出缩短的趋势。

NDVI and MSAVI based on NOAA/AVHRR from 1982 to 1999 are used to monitor variable rules for the growing season of vegetation in northern China. The following, mainly, are included： （ 1 ） an estimation of the beginning, end and length of growing season for each type of vegetation with threshold method and moving average method; the beginning, end and length of growing season of vegetation from 1982 to 1999 linearly fitted; and finally, an analyzation of the linear trend of the beginning, end and length of growing season of vegetation; （2） the area in northern China is divided into 32 --36° N ,36 -- 40°N,40 -- 44°N ,44 -- 48° N ,48 -- 52°N zones in latitudinal direction. The beginning, end and length of growing season in different years and zones are estimated based on greatest changes of slope method, （ 3 ） growing season of vegetation in different spatial locations from 1982 to 1999 are fitted based on curves. Then, the average spatial difference rules of multi-year growing seasons are discussed in article. Results show that ： （ 1 ） Beginning of growing season of most types of vegetation, such as typical steppe, desert steppe and temperate mountain deciduous coniferous forest, has advanced; end has postponed; length has prolonged; and advancing and postponing days are different. Moreover, the beginning of the growing season of less types of vegetation, such as temperate deciduous broadleaf forest, doesnt indicate such a trend, but its beginning has postponed or its end has advanced. （2） Beginning of growing season of desert and nondesert vegetation in most and length has prolonged latitude zones has an exhibition of the trend of the advance, as well as the trend of the postponed, （3） There is early start to the growing season of vegetation in Qinghai, Gansu, southern area of Shannxi and an early end to the growing season of vegetation in Tian mountain of Xinjiang, northern area of Dongbei Qinghai, Gansu. The growing season of most areas in Dongbei, Qinghai, Xinjiang shows a prolonging trend, however, that of some areas show a shortening trend.