Changes of NDVI and its response to climate factors in Ordos City during the growing season

Ordos City is located in a transitional zone between grassland and desert,with a fragile and sensitive ecological environment.In order to study the dynamic changes of vegetation and its response to climate factors,MOD13Q1 data with a resolution of 250 m and meteorological observation data from 2000 to 2023 were used.Theil Sen trend analysis and Mann Kendall test were applied,combined with coefficient of variation,Hurst index,and correlation coefficient to analyze the spatiotemporal variation characteristics,stability,sustainability,and response mechanism of NDVI in the growing season of Ordos City to climate factors.The results showed that the average NDVI in the growing season of Ordos was 0.269,and the growth rate was 0.045/10 a.The significant increase area accounted for 75.03% of the total area of the city,mainly located in the eastern region and the sandy land in the north.The average coefficient of variation of NDVI was 0.18,indicating that the overall stability of vegetation was weak,and vegetation growth was vulnerable to external environment; The average Hurst index was 0.44,indicating that the NDVI may show an anti sustainable downward trend in the future.The effect of precipitation on vegetation growth was greater than that of temperature,and the area with significant positive correlation between NDVI and precipitation accounted for 48.77%,mainly distributed in grassland and sandy land in the West; The proportion of regions with significant positive correlation between NDVI and temperature was 20.15%,which is mainly located in the grassland and farmland with relatively abundant precipitation in the Middle East.The monthly scale analysis showed that the water and heat conditions in July had an important impact on the vegetation growth,and the precipitation in July showed a continuous positive promoting effect on the vegetation growth in the current month and subsequent August and September,while the temperature in July showed a negative inhibiting effect.