Ammonium Compounds 2 Journal Article 2 N762921K75 2 Nitrates 2 Nitrogen 2 Soil 2 ammonium 2 plus ... nitrate 2 nitrogen uptake preference 15N labeling 1 Research Support, Non-U.S. Gov't 1 conifers 1 nitrogen deposition 1 organic nitrogen 1 stable isotopes 1 temperate forests 1 moins ...