Although numerous studies have been conducted on nitrogen (N) cycle, they have focused primarily on N dynamics during the growing season. Accumulating evidences demonstrate that soil N dynamics during winter could greatly influence annual N budget. Climate changes results in increase in snow depth in Mongolia plateaus. At the same time, grasslands in this region are facing high pressure from land use changes. Combining in situ 15N isotope labelling with snow manipulation under different land use practices, we assessed how deepened snow and its interaction with land use changes could affect soil N dynamics of temperate grasslands during non-growing season.
Results/Conclusions
We found that deepened snow reduced total 15N recovery by an average of 21.67% and 19.20% during the first and second winter, respectively. The decreased in 15N recovery was primarily due to that depended snow increased soil temperature and thus microbial activity. The higher microbial activity further resulted in more gaseous N loss. Compared with ambient snow, depended snow increased N2O emission by 57.41% during non-growing season. Although deepened snow reduced soil N recovery, surface soil N concentration was marginally increased after 5 years’ deepened snow treatment, especially for the sites experiencing lower land use intensity. The increase trend in surface soil N concentration was because deepened snow significantly reduced soil N loss via wind erosion, and increased the interception of N-enriched dust due to better vegetation coverage.
Overall, our study demonstrates that winter processes play a critical role in determining annual N budget in temperate grasslands. Deepened snow and land use change could great alter the interaction between biotic and abiotic processes, and thus the balance between vertical and lateral N flux. Soil N dynamics during non-growing season is needed to be considered to improve land management in aeolian landscapes.