Data from: Transformation from NHx to NOy deposition aggravated China’s forest soil acidification

Elevated nitrogen (N) deposition and changes in reduced or oxidized
component contribution greatly affect soil acidification. China has
experienced a significant transformation of N deposition components from
NHx to NOy over the past 40 years, but the effects of component
transformation on soil acidification are poorly understood. Therefore,
long-term monitoring data and literature on N deposition, combined with
the results of isotope experiments, were used to explore the contributions
of different N forms on soil acidification in China’s forests. Here, all
processes related to NHx and NOy, including the transformation to NH4+ and
NO3-, and subsequent N cycling in the soil, were considered. We found that
N-induced soil acidification in 80% area of China's forests was
dominated by NHx deposition, and the other areas (South China) were
dominated by NOy deposition in 2010s. From 1980 to 2019, the average
contribution of NHx was higher than that of NOy but the latter
contribution continued to increase. Meanwhile, the results showed that
soil acidification increased with the decrease of the ratio of NHx to NOy
(RNHx/NOy), this is mainly because NOy is more easily leached in the form
of NO3- than that of NHx under the influence of different plant
preferences and soil retention rates, resulting in a higher net proton
production of NOy. Our research has powerful implications for
policymaking, provides a theoretical basis for formulating different N
reduction policies in different regions, and points out that the
synergistic effect of RNHx/NOy changes should be considered to alleviate
soil acidification.