Nitrogen deposition does not alter the temperate forest soil carbon pool: A 14-y experiment on varied nitrogen fertilization

Soil carbon (C) pools in nitrogen-limited temperate forests are critical to the global C cycle, but there are no long-term experiments examining soil C, with various nitrogen (N) forms. Here, a 14-y experiment (100 kg N ha −1 y −1 ), with added N simulating atmospheric deposition proportions (~70% inorganic, ~30% organic) did not affect soil C pools, whereas organic N (ON) and inorganic N (IN) individually significantly increased values by 2.7-fold and 1.8-fold, respectively. Although no treatment significantly affected soil pH, treatment effects on pH were negatively associated with soil C pools. In addition, treatments containing ON forms increased mineral-associated organic C fractions, indicating enhanced C stability vs. IN. These findings enhance our understanding of N deposition-soil C pool interactions.