Tracking the fate of deposited nitrogen and its redistribution in a subtropical watershed in China

Vegetation cover and soil infiltration can result in nitrogen (N) redistribution and associative isotopic fractionation. This study investigated N and its isotopic characteristics from deposition to baseflow under different vegetation canopy cover types in a subtropical watershed in China. Results showed that canopy interception via vegetation cover types exhibited notable dilution effects on reactive nitrogen (N r ) deposition during the rainy season, with the highest maximum value of 287.4%. The range of δ 15 N changed from 3.0‰ to 11.9‰ in throughfall, which may have resulted from an increase in N taken up by vegetation and particles washed away from plant leaves during rainfall events. Throughfall, soil water, precipitation, and rainfall run‐off were the sources of D and 18 O‐H 2 O in baseflow river water, wherein the rainwater and rainfall run‐off contributed 73% ± 8% and 15% ± 12%, respectively. Soil water was the main source of 15 N‐NO 3 in baseflow river water, which contributes 78% ± 4% of overall source, but precipitation only contributes 10%. The average annual N r deposition flux was 24.4 ± 4.2 kg·ha −1 ·yr −1 , whereas the annual total nitrogen exportation flux was 1062 ± 269.8 kg·yr −1 . The 46% of HDO or D 2 O for river water came from rainfall run‐off, which would transport a maximum nitrate flux of 354 kg·yr −1 . Moreover, vegetation cover and soil infiltration resulted in δ 15 N enrichment and a decrease in N r in river flow.