Spatial distribution and driving factors of sediment net nitrogen mineralization in riparian zone of the Three Gorges Reservoir

Authors：Jia Kai-tao; He Li-ping^*; Ke-hong, Wang; Yu Zhi-guo; Liang Li-jiao; Yu Zhuo-lin; Lin Jun-jie^*

Source：Journal of Mountain Science, 2023, 20(2): 381-390.

DOI：10.1007/s11629-022-7691-0

• Inorganic nitrogen loss
• Sediment physicochemical properties
• Drying period
• Substrate quality
• Net nitrogen mineralization rate
• Temperature sensitivity

Inorganic nitrogen (N) loss through sediment N mineralization is important for eutrophication surrounding riparian zone. Sediment physicochemical properties have been changed at water-level elevation in riparian zone of the Three Gorges Reservoir (TGR) due to differences in hydrological stress and human activity intensity. However, spatial distribution and driving factor of net N mineralization rate (N-min) and its temperature sensitivity (Q(10)) based on the changes in sediment physicochemical properties are still unclear at water-level elevation in the riparian zone. A total of 132 sediment samples in the riparian zone were collected including 11 transections and 12 water-level elevations on basin scale of the TGR during drying period, to conduct a 28-day incubation at 15 degrees C, 22 degrees C, 29 degrees C and 36 degrees C. N-min, total N (TN) and substrate quality (SQ) increased with water-level elevation, while Q(10) showed an opposite trend (P<0.001). Results of the structural equation model showed that water-level elevation had direct positive effects on TN and SQ (P<0.01). In addition, TN was the major factor that had a direct positive effect on N-min, and SQ was the crucial factor that had a direct negative effect on Q(10) (P<0.001). In conclusion, increases in TN and SQ were major driving factors of N-min and its Q(10) at water-level elevation, respectively, in riparian zone of the TGR during drying period.