天津植被指数对气候因子响应的敏感性分析

探索植被覆盖与气候变化相互关系是全球环境变化研究领域的重要内容之一,研究特定区域植被对气候变化响应特征对植被重建和生态恢复具有重要意义。然而,目前植被对气候因子响应的敏感性研究还十分缺乏。利用1982—2003年8km×8km的NASA/GIMMS半月合成的归一化植被指数（NDVI）和同期气候数据,研究了天津地区NDVI对气候因子响应特征及其敏感性。结果表明：植被NDVI与气温及降水均有显著非线性正相关关系（P〈0.0001）;在半月平均气温低于0℃时,植被NDVI与气温没有显著性相关,而从气温高于0℃,一直到高于22℃,NDVI与气温的关系均达到显著性水平（P〈0.05）,但相关性是逐渐降低的;当半月平均气温高于23℃及以上时,NDVI与气温没有显著的相关关系（P〉0.05）;当半月降水量〉0mm时,NDVI与降水存在极显著正相关关系（P〈0.0001）,随着降水量的增加,相关关系减弱,在降水量大于50mm时,NDVI与降水没有显著相关关系（P〉0.05）;研究结果证实,天津地区植被指数对气候的响应存有明显的非线性特征,在低温和低降水量条件下植被的响应更为敏感,23℃和50mm分别是该地区影响植被生长的气温和降水阈值。结合1982—2003年逐半月气候条件分析发现,气温的影响主要是春、秋两季,而降水的影响主要表现在春、秋及夏初。

Sensitivity analysis on response of NDVI to climate factors in Tianjin

Investigating the relationship of vegetation cover with climatic variation is one of the major aspects of global environmental change studies.Research on response of vegetation variability to climate change is of ecological significance for vegetation reconstruction and eco-environmental restoration.It is,however,rather limited for study on response sensitivity of vegetation to climate change.Using semi-monthly averaged NASA/GIMMS NDVI with a spatial resolution of 8 km×8 km and local climatic data from 1982 to 2003,we analyzed response characteristics and sensitivity of NDVI to climatic factors.Results showed that semi-monthly NDVI was nonlinearly and positively correlated with both temperature and precipitation over the same period（P 〈0.0001）.There was no significant correlation between NDVI and temperature when semi-monthly temperature is lower than 0 ℃.However,NDVI was significantly correlated with temperature while semi-monthly temperature is higher than from 0 ℃ to 22 ℃（P〈 0.05） although significance level declined gradually.At the temperature up to 23 ℃ or above,semi-monthly NDVI showed no significant correlation with temperature（P〉 0.05）.When semi-monthly precipitation is more than 0mm,NDVI was significantly and positively correlated with precipitation.With the increase of precipitation,the statistical significance was gradually down.Until precipitation up to 50 mm,no significant existed between NDVI and precipitation（P 〉0.05）.The results in the present study indicate that there is apparent nonlinear characteristic in the response of NDVI to climate in Tianjin area.At low temperature and precipitation conditions,the vegetation is more sensitive,and the threshold for temperature and precipitation determining plant growth is 23 ℃ and 50 mm,respectively.Combination of semi-monthly climatic condition,it is found that the effect of temperature on NDVI focuses on spring and autumn,whereas for precipitation,the effect dominantly lies in spring,autumn and early summer.