Abstract: Using the univariate linear trend method and buffer analysis,this study analyzed the spatio-temporal variation characteristics of the normalized difference vegetation index(NDVI)and enhanced vegetation index(EVI)in nature reserves in Yunnan Province.The differences in the conservation effectiveness evaluation results based on NDVI versus EVI were compared.The results showed that from 2000 to 2023,the NDVI/EVI indices of most nature reserves in Yunnan Province exhibited significant or highly significant growth.NDVI showed minor fluctuations,EVI exhibited more pronounced fluctuations.On the one hand,this indicates improving vegetation growth and effective conservation in Yunnan’s nature reserves.On the other hand,it shows that vegetation ecological stability characterized by NDVI is more stable than that characterized by EVI.Certain differences exist in the conservation effectiveness results for some nature reserves based on the two vegetation indices.From the perspective of NDVI/EVI change trends,nature reserves in Yunnan Province exhibit pronounced spatial heterogeneity and clustering.conservation effectiveness is better in the eastern, western, and southwestern parts of Yunnan. However, in northwest Yunnan, the number (and area) of nature reserves with poor conservation effectiveness identified by EVI is significantly larger than that identified by NDVI

Key words:  vegetation index, normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), nature reserve, Yunnan Province