A framework for assessing the effects of afforestation and South-to-North Water Transfer on nitrogen and phosphorus uptake by plants in a critical riparian zone

The uptake of nitrogen (N) and phosphorus (P) by plants in riparian zones can significantly decrease the water pollution risk. Moreover, the vegetation area in riparian zone can be impacted by raising of water level and afforestation. As the largest reservoir in North China, the Miyun Reservoir is affected by the South-to-North Water Transfer (SNWT) and large-scale afforestation. However, few efficient technology frameworks that can be used to assess the effects of similar anthropogenic projections on N and P uptake by plants at riparian zone catchment scale have been reported. Therefore, this study proposed a framework including an ecological simulation tool coupled with multi-source data and scenario setting methods to identify the effects of these two projects on the uptake of N and P by plants in Miyun Reservoir riparian zone from April to September in 2015. The results show that the total N and P uptake by plants in Miyun Reservoir riparian zone are 1214.18 t and 148.66 t in growing seasons. After afforestation, the N (P) removal will increase by 2.56 (2.17) times in the impacted area (below 160 m in elevation). When the water level rises to 150 m in elevation, the joint effects of afforestation and SNWT will increase the total N and P removals by 851.18 t and 83.33 t. This implies that the afforestation can offset the negative effect on N (P) removal caused by SNWT. Overall, this study can provide useful scientific reference for the design and effective management of the riparian zone.