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NDVI能够反映地表覆盖和生态环境变化。在祁连山东延余脉采集树轮样本,分析树木径向生长与植被NDVI的相关关系,并重建历史时期植被NDVI变化。结果表明:树木径向生长与夏季NDVI受到水热条件变化的显著影响,且树轮宽度与夏季NDVI显著正相关,采用简单线性回归方法建立二者的拟合方程,方差解释量达0.600(R2adj=0.582,F=34.472,P<0.0001);公元1845年以来,重建的NDVI序列显示植被覆盖相对较低时期有19世纪60年代,80年代初期,20世纪初期和20-30年代,其中20世纪20-30年代NDVI低值期与中国北方大范围旱灾一致;重建的NDVI与旱涝指数显著负相关,证实重建NDVI序列的可靠,且显示该区旱涝演化趋势;周期分析表明公元1845年以来,NDVI序列存在2-3年、5年左右、13年左右和15年左右的振荡。
NDVI can reflect the change of surface cover and ecological environment. Tree ring samples were collected from the extension of the eastern Qilian Mountains to analyze the relationship between tree radial growth and vegetation NDVI and to reconstruct vegetation NDVI changes during the historical period. The results showed that the radial growth of trees and summer NDVI were significantly affected by the changes of water and heat conditions, and the tree wheel width was significantly and positively correlated with summer NDVI. The simple linear regression method was used to establish the fitting equation between the two. The variance explained was 0.600 (R2adj = 0.582, F = 34.472, P <0.0001). Since 1845, the reconstructed NDVI sequences showed relatively low vegetation cover in the 1960s, early 1980s, early 20th and 20-30 years, of which the 20th century The low NDVI in 20-30 years is consistent with the large-scale drought in northern China. The reconstructed NDVI is significantly negatively correlated with drought and flood index, confirming the reliable NDVI sequence and showing the evolution of drought and flood in this area. Periodic analysis shows that since 1845 , NDVI sequence exists 2-3 years, 5 years, 13 years and 15 years of oscillation.