Fig. 4

Spatial distribution of OLDI in the Sanjiangyuan Region from 2001 to 2023. (a) OLDI distribution in 2001. (b) OLDI distribution in 2005. (c) OLDI distribution in 2010. (d) OLDI distribution in 2015. (e) OLDI distribution in 2020. (f) OLDI distribution in 2023.