Long-Term 15N Balance After Single-Dose Input of 15N-Labeled NH4+ and NO3− in a Subtropical Forest Under Reducing N Deposition,Global Biogeochemical Cycles

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Long-Term 15N Balance After Single-Dose Input of 15N-Labeled NH4+ and NO3− in a Subtropical Forest Under Reducing N Deposition
Global Biogeochemical Cycles ( IF 5.4 ) Pub Date : 2021-07-03 , DOI: 10.1029/2021gb006959
Danni Xie ₁ , Lei Duan _{2,

3} , Gaoyue Si ₄ , Wenjing Liu ₅ , Ting Zhang ₆ , Jan Mulder ₇

Affiliation

Nitrogen (N) deposition in Europe and North America decreased in the 1990s, whereas N deposition in China began to decline in the early 2010s. The response of temperate forests to decreasing N deposition implied a delay recovery, but it remains unknown whether recovery in subtropical forests follows a similar trend. Therefore, the effects of decreased N deposition on N leaching were simulated in an N-saturated forest in southwest China following ten years of N application 4.00 g N m⁻² yr⁻¹. The addition of N (NH₄⁺ or NO₃⁻) was stopped in 2014. In 2017, a single in-situ ¹⁵N addition as NH₄⁺ or NO₃⁻ was performed to trace the fate of N under reducing N deposition. Combining the monitoring results of the N fluxes and ¹⁵N fates, both the actual N leaching and contribution of a “new” N input to N leaching were significantly reduced in response to decreasing the N input. The termination of N addition resulted in immediate decreases in the N mineralization and immobilization rates, which were even lower than those in the control plots with moderate (naturally occurring) deposition reduction. The ratio of N leaching from mineralization was also reduced, implying the critical role of N mineralization in the recovery from N saturation. Because the forest was still N-saturated, decreasing N deposition slightly reduced the N leaching to the gross N input ratio (including both N deposition and N mineralization). The significant decrease in the ratio and thus leaching recovery may occur due to a significant N deposition reduction.

更新日期：2021-07-28

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