近20年天津地区植被变化及其对气候变化的响应

Dynamic change of vegetation cover and its reponse to climate change in recent 20 years in Tianjin area

植被与气候变化的相互关系在全球或区域尺度上得到了证明。研究特定地区植被动态变化及其与气候变化的关系,找出影响植被变化的关键因子,是植被重建和生态环境恢复的前提。文章利用1982～2003年8km×8km的NASA/GIMMS半月合成的植被指数(NDVI)数据和同期气候数据,分析了天津地区植被的年平均NDVI的动态变化规律及其与年平均温度和年降水的关系。结果表明:1982—2003年,年平均NDVI呈现波动性的逐渐降低趋势,并且年代际变化特征明显;近20年来,天津年平均温度明显升高,而年平均降水量总体上呈减少趋势,指示天津地区暖干化趋势明显;统计分析表明研究区年平均温度对植被指数的年际变化没有明显的影响(P>0.05),而年降水与植被指数呈显著正相关(P<0.01)。本研究证实由于天津地区持续干旱化的影响,植被生长状况逐渐向差的方向发展,降水的多寡是植被生长优劣的决定性因子,改善水分状况是推进该地区植被恢复与重建的关键因素。

The relationship of vegetation with climate change has been identified by recent studies in regional and global scales. It＇s the basis for vegetation reconstruction and eco-environment restoration through research on vegetation dynamics in specific region and its relationship with climate change to find the key factor affecting vegetation changes. In this study, the dynamic change of the annual mean NDVI in Tianjin area and its relationship to temperature and precipitation was analyzed based on 8 km NASA/GIMMS NDVI data and corresponding climate data from 1982 to 2003. The results indicated that the annual mean NDVI gradually decreased with fluctuation from 1982 to 2003, with an obvious interdecadal variation. In the recent 20 years, annual mean temperature in Tianjin area significantly increased, whereas annual precipitation showed negative pattern, indicating a warm-drying trend of climate. Statistical analysis showed that there was no significant relationship between NDVI and temperature （P〉0.05）, whereas a positive correlation was found between NDVI and precipitation （P〈0.01）. The results in this study confinned that growing status of plants mainly is becoming bad due to continuous drought in recent years in Tianjin area. The mount of precipitation is determinant factor for plant growth. Therefore, improving the climatic condition, especially water status is the most important factor to reconstruct and restore vegetation in this area.