Temporal and spatial characteristics of grassland ecosystem service value and its topographic gradient effect in the Yellow River Basin.

Grassland is the largest terrestrial ecosystem in the Yellow River Basin and an important ecological barrier in the basin. Scientific and accurate estimation of the service value of grassland ecosystems in the Yellow River Basin is of great significance for maintaining the ecological security of the Yellow River Basin. This study was based on Constanza, a method based on the correction of natural grassland ecosystem service value in the Yellow River Basin. This method considers grassland biomass, estimates the ecological service value of each type of grassland item by item, and analyzes their spatial distribution and topographic gradient differentiation characteristics. The results showed that the unit price of soil conservation services provided by the grassland ecosystem in the Yellow River Basin has an advantage (6.2 times) which is the lowest unit price of raw materials. The total value of grassland ecosystem services in the Yellow River Basin is 100.82 × 1010 Yuan. Among the various services, the adjustment service has the largest value, accounting for 50.56% of the total value, while the sum of the supply service, support service and cultural service amounted to 49.44%. The high-value areas of grassland ecosystem services are mainly distributed in the upper and lower reaches of the basin, as the low-value areas are located in the Ningxia and Hetao Plains and most parts of the Loess Plateau. The ESV per unit area of grassland in the Yellow River Basin showed a decreasing to increasing trend with the increase in elevation and topographic relief, as the ESV continued to increase with slope increase.