A comprehensive evaluation of soil quality in the Three River Headwaters Region, China

Soil quality in the Three River Headwaters Region (TRHR) has a direct connection with the vegetation restoration and ecosystem health of the whole region, however, the evaluation of soil quality on a regional scale is still lacking. We analyzed the distribution pattern of the regional soil quality index (SQI), explored the dominant factors affecting SQI, and proposed measures to improve soil quality based on 638 soil samples collected at surface soil and subsurface soil. The results showed that in the TRHR, the SQI was higher in the southeast, and lower in the northwest. The average SQI were 0.52 for surface soil and 0.50 for subsurface soil, indicating better soil quality in the surface soil. Among different vegetation types within the TRHR, the SQI was ranked as follows: the alpine shrub (0.52–0.55) > the alpine meadow (0.51–0.52) > the alpine steppe (0.44–0.45). The study explored that NDVI was the dominant factor driving SQI, with geographical and climatic factors indirectly affected it through vegetation. This study proposes the corresponding strategies based on the distribution of SQI in different vegetation types and its main driving factor for the better development of soil quality in the TRHR, and it can provide practical guidance for remediating degraded soil, restoring degraded vegetation, and alleviating the impact of climate change. • The SQI varies significantly in different soil layers and vegetation types. • Vegetation had the strong control on the soil quality in the TRHR. • Ecological restoration strategies of different vegetation types were proposed.