干旱区生态环境知识资源中心

Time lag cross correlation method is adopted to conduct analysis on intra-annual time lag response of vegetation coverage to hydrothermal condition based on ten-day average air temperature, precipitation data and Systeme Probatoire d’Observation de la Terre -normalized difference vegetation index (SPOT-NDVI) data in energy enrichment zone in the north of Shaanxi from 1999 to 2010. The vegetation coverage in the south of energy enrichment zone was better, characterized by high degree of correlation between ten-day NDVI (TN), ten-day mean temperature (TT) and ten-day precipitation (TP), correlation coefficient of more than 0.9, rapid response, lag time being 10 to 20 days. The windy sand grass shoal area in the south end of Mu Us desert was characterized by low degree of correlation between TN with TT and TP, correlation coefficient from 0.75 to 0.85 and longer response time, lag time for 30 to 50 days in most part of the zone, indicated that the zone with better hydrothermal condition was higher in degree of correlation and rapid in response speed and that the zone with poor hydrothermal condition was lower in degree of correlation and slow in response speed. Level of influence of Intra-annual change of air temperature on NDVI of vegetation is on the decrease from south to north. The response of vegetation to intra-annual precipitation was similar to temperature. The research finding may offer theoretical basis for optimization of type of vegetation planted in energy enrichment zone in the north of Shaanxi.