Abstract:

Using MOD13Q1 data and meteorological observation data from 2000-2020, the temporal and spatial variation of the Normalized Difference Vegetation Index (NDVI) and its climatic response in Hulun Buir were analyzed using Sen trend analysis, M-K significance test, coefficient of variation, Hurst index, and correlation coefficient methods.The results show that the annual average NDVI in Hulun Buir is 0.63 during the growing season, and the annual average tendency rate is 0.028 per decade.Most regions show an increasing trend, especially in most forest areas and farmlands in the west of Daxing'anling.The average coefficient of variation in NDVI in Hulun Buir is 0.08 during the growing season, and the fluctuation in the grassland distribution in the western part of Hulun Buir is larger.The Hurst index indicates that the overall change of NDVI in the Hulunbuir area during the growing season shows an anti-persistent trend.Combined with the current change trend of NDVI, it shows a downward trend in the future, which is unfavorable to the protection of the ecological environment.As a whole, there is a positive correlation between NDVI and temperature in the forest during the growing season, while negative correlation between cultivated land and grassland.Generally, precipitation has a positive correlation with NDVI in most areas of Hulun Buir during the growing season, especially in cultivated land at the foothills of Hulun Buir grassland and Daxing'anling.That indicates that temperature is the main factor to mediate forest growth in northern Daxing'anling, while precipitation restricts the ecological balance between Hulun Buir grassland and the development of agriculture and animal husbandry.

Key words: Sen trend analysis, Hurst index, Climate change