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[摘要]
基于连续时间序列的SPOT/VEGETATION NDVI卫星遥感数据和气象数据,利用PenmanMonteith、反距离加权插值、相关分析等方法,以河北省为研究对象,深入探讨植被动态特征及气象干旱影响。结果显示:河北省多年平均归一化植被指数(NDVI)在时间尺度上呈波动上升趋势,尤其在2003年开始出现0.028/(10 a)的飞跃增长,空间尺度上呈现中部高两侧低的分布特点;河北省气温上升趋势显著,空间分布呈西北—东南增加趋势,降水量从西北部—中部—东北部呈现低—中—高的分布格局;春季发生干旱的面积及频率皆为最高,夏季干旱高频地区位于唐山、张家口地区,秋季干旱频率最低,冬季以轻旱为主;植被NDVI与标准化降水蒸散指数(SPEI)相关性夏季最强(0.529),春秋季次之,冬季相对较弱;年尺度上,以蔚县站、张北站和承德站为中心区域主要为显著负相关,显著正相关主要分布于中部地区。研究结果可为生态系统管理部门制定科学合理的植被建设决策提供参考依据。
[Key word]
[Abstract]
Vegetation as an important part of the terrestrial ecosystem,it links the atmosphere,hydrosphere,and soil circle,and is a reflection and indication of regional climate characteristics.With the construction advancement of the ThreeNorth Shelterbelt and the conversion of farmland to forest and grassland,vegetation growth is being affected by human activities.Hebei Province has a forest coverage rate of 34% by the end of 2018.At the same time,it has fully promoted the threeyear national land greening initiative.In 2019,684,000 hectares of afforestation were completed,accounting onetenth of the total number of afforestation in the country.The semihumid and semiarid continental monsoon climate in Hebei Province and the geographical location of the farmingpastoral zone determine its ecological environment selfregulation ability,and it is extremely vulnerable to meteorological disasters,especially drought.Therefore,in the context of global warming,the accelerated frequency of climate extremes,and the increase in the intensity of human activities,comprehensive exploration of vegetation growth characteristics and attribution analysis has an important practical significance. The research methods include SPEI (standardized precipitation evapotranspiration index) and correlation analysis.The SPEI index not only considers precipitation and evapotranspiration but also retains the sensitivity to temperature and precipitation such as SPI (standardized precipitation index) and PDSI (palmer drought index).Describing drought objectively,correlation analysis and the inverse distance weighted interpolation method is used in ArcGIS,SPEI raster map combined with NDVI image to calculate the spatial correlation distribution map of NDVI and SPEI,and conduct a significance test to analyze the spatial relationship between NDVI and drought index. Hebei Province′s multiyear average NDVI fluctuates and rises on the time scale,especially in 2003,and it display a rapid increase of 0.028/(10 a),showing the distribution characteristics of high and low in the middle on the spatial scale.The increase of temperature is significant,and the spatial distribution shows an increasing trend from northwest to southeast in Hebei Province.Precipitation presents a low-medium-high distribution pattern from northwestcentralnortheast.The area and frequency of droughts are the highest in spring,and the high frequency area of summer drought is located in Tangshan in Zhangjiakou,the frequency of drought is the lowest in autumn,and light drought is dominant in winter.The correlation between vegetation NDVI and SPEI is strongest in summer (0.529),followed by spring and autumn,and relatively weak in winter.The central area of Yuxian Station,Zhangbei Station and Chengde Station are mainly negatively correlated,and the positively correlated are mainly distributed in the central region. Conclusions (1) The multi-scale SPEI (1/3/12) value of Hebei Province has a large range of changes,and the seasonal drought has obvious changes with phase characteristics,which mostly occur in spring,summer and winter.The annual scale SPEI judgment shows that the drought is serious and has a large deviation "Hebei Meteorological Bulletin".The seasonal scale SPEI value shows the drought situation in Hebei Province is more reasonable,but there is a degree of deviation in some years.(2) The correlation between NDVI and SPEI on a seasonal scale,with the strongest correlation in summer,followed by spring and autumn,and the weakest in winter.On the annual scale,the correlation between vegetation NDVI and SPEI has obvious regional differences.
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