Patterns of nitrogen processes across soil mineral nitrogen gradient in terrestrial ecosystems: A global synthesis

Background/Question/Methods The enhanced nitrogen (N) deposition has largely increased soil mineral N concentration in terrestrial ecosystems. However, how N cycling processes change with soil mineral N is still unclear. Furthermore, the current N cycling and C-N coupling models have some limitations to simulate N processes of soil mineral N. In this study, we synthesized the results of 197 individual studies to explore the patterns of N cycling processes across soil mineral N gradients at individual, biome, and global levels.

Results/Conclusions Our results showed a diverse pattern in individual studies (e.g., linear, quadratic, exponential and no trend) for N cycling processes. Interestingly, N cycling processes showed clear patterns at global level. For example, In-situ and potential N mineralization and N fixation rates exhibited quantic relationships with soil mineral N, while in-situ potential N₂O emission rates increased exponentially across soil mineral N gradient. N uptake rate has exponential increased to a maximum. Soil N leaching and volatilization were both found significant linear correlated with soil mineral N. At biome level, however, the trend differed for most of the processes except for potentials mineralization. Our study revealed clear patterns of N cycling processes across soil mineral N gradient which provides useful information for future modeling and experimental studies.