Abstract:
Objective The process of soil nitrogen mineralization in the bank zone of the Three Gorges Reservoir has a significant impact on water eutrophication and ecological security of the Three Gorges reservoir. However, the response and driving factors of soil nitrogen mineralization to warming have not been paid attention.
Method A total of 108 topsoils were collected from the riparian area (elevation 145-155 m, 155-165 m, 165-175 m) and the non-flooded area (elevation 175-185m) of the Three Gorges Reservoir bank zone in nine sections of the Yangtze river. The soils were incubated at 15, 22, 29 and 36℃ for 28 days. The contents of soil ammonium nitrogen and nitrate nitrogen before and after incubation were measured, and the net ammoniation rate, net nitrification rate and net nitrogen mineralization rate and their response to warming were calculated.
Result The results showed that the soil net nitrification rate and net nitrogen mineralization rate in the reservoir bank were significantly positively correlated with the elevation under the four temperatures (P < 0.05), but the net ammoniation rate had no significant difference between the elevations (P > 0.05). In general, the temperature sensitivity (Q10) of the net nitrogen mineralization rate in the reservoir bank is between 0.62 and 3.21, and the soil net nitrogen mineralization in the riparian area is more sensitive to warming than that in the non-flooded area. Rainfall is the common driving factor of Q10 change in the riparian area and non-flooded area. In addition, Q10 in the riparian area was significantly negatively correlated with elevation, pH value, annual precipitation, microbial biomass carbon (P < 0.05) and the distance to the Three Gorges Dam (P < 0.01).
Conclusion Therefore, it is expected more nitrogen in the riparian area will enter the water through mineralization, thus increasing the eutrophication load of the Three Gorges reservoir in the context of global warming.
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