Long-term stabilization of 15N-labeled experimental NH4+ deposition in a temperate forest under high N deposition

High nitrogen (N) deposition levels, currently present in many industrial and agricultural regions of the world, can strongly affect functioning forest ecosystems. In a pine with strong N leaching, located Netherlands, we studied long-term fate year-long NH4+ cohort labeled 15N. A high ambient low treatment had been established at site by means roof sprinklers. Resampling pools 19 years after labeling 11 last sampling, found similar 15N deltas needles, twigs LF1 organic soil layer each treatment, indicating intensive cycling among these pools. years, label recovery decreased labile pools, while remained constant wood increased bark. Together aboveground vegetation retained less than 3% N. layers, to 23% both treatments, mineral it from 4% 13% (high N) 29% (low treatment). Within was mainly fine roots, most incorporated two density fractions, shifting fraction depth. This suggests capacity incorporate After lost substantially previous especially first, its presence 38% 54% Apparently, even this leaching ecosystem, once incorporated, well did not input-output fluxes system.