## 4 Discussion  
The overall ESV of the study area was CNY 26,297.967 million, and the area share of each land use type in the study area was in the following order: paddy field > broad-leaved forest > built-up land > scrub > artificial wetland > water system > coniferous forest > natural wetland > grassland, and the corresponding ESV share of each land use type was in the following order: water bodies > broad-leaved forest > artificial wetland > scrub > paddy field > coniferous forest > natural wetland > grassland. Among the various types of ESVs in the study area, the ESV of water bodies accounted for the highest proportion, with a total amount of CNY 894.5469 million, accounting for 34.02%, and its provisioning service value was the most prominent, accounting for 65.844% of the value of all ecosystem provisioning services, followed by the regulating service value, with a proportion of 38.80%. Next, broad-leaved forest ecosystems accounted for 20-40% of the overall ESV. However, the ecosystems of paddy fields, which accounted for the largest area of land use types in the study area, all accounted for less than 11% of the ESV of all types and supplied CNY \(-\)570.818 million, accounting for \(-\)57.14% of all ecosystem supply service values. The provisioning service value of the paddy field ecosystem was negative because the paddy field ecosystems in the study area were dominated by rice cultivation, which consumes a large amount of water resources during the growth process, and its water conservation function is weak and shows a negative growth trend; if the paddy field areas were transformed into other types of ecosystems, the provisioning service value would increase [28; 29; 30; 31; 43]. The artificial wetlands in the Guangdong section of the Xijiang River mainstream are a relatively unique type of wetland. It is mainly used for the aquaculture of fish and shrimp and other aquatic products, with a regular layout, presenting low species richness compared with natural wetlands, reflecting the influence of factors such as market demand and the government's subjective willingness to make decisions on the landscape ecosystems. In the course of this study, based on the different wetland utilization patterns in the study area, the ESV equivalent factor of artificial wetlands in the Guangdong section of the Xijiang River mainstream was corrected using the shadow engineering method, which distinguished the ESV of artificial wetlands from that of natural land and was conducive to the explanation of the differences in the service value of the same area of artificial and natural wetland site types. However, the correction method is rough and needs to be further subdivided by the local aquatic products' aquaculture price data and the impacts of farmland and aquaculture on the artificial wetland ecosystems to explore a more realistic artificial wetland ESV equivalent factor. Within the 1 km gradient along the river, as an important interface between water and land, which is the most frequent and intense area of material exchange and energy flow in the land-water interface zone, the value of the water bodies is ES-dominated, contributing to about 80% of the provisioning services and 85% of the regulating services. Then, as the distance from water increases, the ecosystems of the water bodies gradually transition to ordinary terrestrial ecosystems. Instead, the service value of artificial wetlands and broad-leaved forest ecosystems gradually dominate, with the artificial wetland ecosystems having the highest service value in the 2-5 km gradient along the river and broad-leaved forest ecosystems having the highest service value in 6-10 km gradient along the river. Waters and wetlands play a positive role in flood control, water purification, and soil conservation and are an irreplaceable part of regional socio-economic development.