Quantifying responses of climatic and anthropogenic factors on vegetation normalized difference vegetation index...

Climatic change and anthropogenic activities have substantially influenced vegetation distribution in recent decades. However, identifying the dominant driving factors of vegetation variation remains challenging.

This study investigated vegetation dynamics and quantified their responses to climatic factors (effective precipitation (EFPR) and active accumulated temperature ≥10 °C (ACTE)) and anthropogenic activities (urbanization, afforestation, and cultivation) for the Yellow River Basin (YRB).

The results showed that the YRB experienced vegetation greening in NDVI (as measured by normalized difference vegetation index, NDVI) during the period from 2001 to 2020. More than 90% of the regions in the YRB showed an increasing NDVI trend, with mean rates of 0.055 per decade. In regions with significant (p < 0.05) variations in NDVI, ERPE, ACTE, and anthropogenic activities contributed to vegetation dynamics at rates of 0.012 per decade, 0.007 per decade, and 0.036 per decade, respectively. Contributions of climatic and anthropogenic factors accounted for 35% and 65% of the total NDVI variations, respectively.

Both climatic and anthropogenic factors drove the vegetation growth. In the alpine source regions of the Yellow river, climatic factors were the primary drivers of significant NDVI change. In the MB_YRB (middle basin) and the LB_YRB (lower basin), human activities were the main factors driving vegetation greening. Only in areas with urban agglomeration, such as Xi'an, Zhengzhou and Xi'ning cities, were anthropogenic activities associated with vegetation browning.