Abstract
Atmospheric nitrogen (N) deposition is recognized as a pivotal nutrient input in forest ecosystems. However, significant gaps persist in our comprehension of the global-scale fate of N in forest ecosystems. In a pioneering effort, this study analyzed the fluxes and determinants of deposited N by 234 observations from 52 published articles. Our findings indicated that plant uptake, soil retention, and N losses, respectively, accounted for 27.4, 57.9, and 14.6% of the total deposited N. The fate of deposited N was significantly influenced by a suite of factors, including forest type, climatic parameters such as mean annual temperature (MAT) and precipitation (MAP), edaphic characteristics such as soil pH and the carbon to nitrogen ratio (C/N), and experimental factors like nitrogen addition rate (NR), nitrogen forms (NF), plot size (PS) for (15)N studies, and the duration of study. For the uptake of deposited N, MAP emerged as the predominant positive factors, whereas NR was the dominant negative factors; for deposited N soil retention, NR was the key positive factors, while MAT was the key negative factors; for N losses, MAP was the predominant positive factors, with the C/N ratio serving as a significant negative factor. Thus, for a given forest ecosystem with relatively stable climate and soil conditions, NR, NF, and the soil C/N were the main controlling factors regulating the fate of deposited N. These insights significantly advance our grasp of the N cycle in forest ecosystems. Consecutive monitoring of the impact of deposited N on soil N transformations and carbon sequestration is needed in future studies.