Spatial-temporal analysis of the changes in Populus euphratica distribution in the Tarim National Nature Reserve over the past 60 years

P. euphratica in the Tarim National Nature Reserve has been included in the tentative list of Chinese World Heritage Sites due to its rarity and its ecological and aesthetic value. The temporal and spatial changes in P. euphratica forests in the Reserve from 1964 to 2020 have been monitored to analyze and discuss the human activities and natural condition factors that influence P. euphratica distribution based on multisource remote sensing data, including Corona, SPOT series, Sentinel-2, and Landsat series data. In the Reserve, P. euphratica was originally distributed mainly along the Tarim River channel and within 3 km of it, but gradually contracted from the upper to the lower region river with the impact of the river drying up. It has diminished significantly with the rapid expansion of farmland over the past 60 years, especially from 1995 to 2015, which was a period of rapid agricultural development. The influence of cultivated land on P. euphratica was significant along the Tarim River and within 1 km of it, while it was weakened beyond 1 km. The occurrence of P. euphratica declined with an increase in soil salinity, and it was highly restricted under extremely salinized soil conditions. P. euphratica appeared more frequently within 3 km of the river channel because the natural conditions with high groundwater levels and mild soil salinity are more suitable for its distribution, and degradation is less likely, except when impacted by human disturbance. Areas of farmland increased from 1964 to 2020, severely salinized soil along the Tarim River within 3 km increased from 1995 to 2020, and the downstream region of the Tarim River dried up in the Reserve. Therefore, we should ensure that we rationally utilize water resources, reduce land cultivation, and control soil salinization to protect P. euphratica from degradation.