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Nitrogen addition, rather than altered precipitation, stimulates nitrous oxide emissions in an alpine steppe

Citation

Yang, Yang et al. (2022), Nitrogen addition, rather than altered precipitation, stimulates nitrous oxide emissions in an alpine steppe, Dryad, Dataset, https://doi.org/10.5061/dryad.fj6q573vz

Abstract

Anthropogenic-driven global change, including changes in atmospheric nitrogen (N) deposition and precipitation patterns, is dramatically altering N cycling in soil. How long-term N deposition, precipitation changes, and their interaction influence nitrous oxide (N2O) emissions remains unknown, especially in the alpine steppes of the Qinghai-Tibetan Plateau (QTP). To fill this knowledge gap, a platform of N addition (10 g m−2 yr−1) and altered precipitation (± 50% precipitation) experiments was established in an alpine steppe of the QTP in 2013. Long-term N addition significantly increased N2O emissions. However, neither long-term alterations in precipitation nor the co-occurrence of N addition and altered precipitation significantly affected N2O emissions. These unexpected findings indicate that N2O emissions are particularly susceptible to N deposition in the alpine steppes. Our results further indicated that both biotic and abiotic properties had significant effects on N2O emissions. N2O emissions occurred mainly due to nitrification, which was dominated by ammonia-oxidizing bacteria, rather than ammonia-oxidizing archaea. Furthermore, the alterations in belowground biomass and soil temperature induced by N addition modulated N2O emissions. Overall, this study provides pivotal insights to aid the prediction of future responses of N2O emissions to long-term N deposition and precipitation changes in alpine ecosystems. The underlying microbial pathway and key predictors of N2O emissions identified in this study may also be used for future global-scale model studies.

Methods

The experiments consisted of six different treatments (NP: ambient nitrogen with ambient precipitation; NP−: ambient nitrogen with 50% reduced precipitation; NP+: ambient nitrogen with 50% increased precipitation; N+P: nitrogen addition with ambient precipitation; N+P−: nitrogen addition with 50% reduced precipitation; N+P+: nitrogen addition with 50% increased precipitation). We monitored the N2O flux during the 2020 growing season (May to October) based on in-situ experiments. To identify the key abiotic and biotic factors regulating N2O emissions, we measured N2O flux on six consecutive days in mid-August (during peak plant growth). Soils were also collected to measure abiotic parameters and functional microbes, including nitrifiers (ammonia-oxidizing bacteria: AOB; ammonia-oxidizing archaea: AOA) and denitrifiers (nirS-, nirK-, and nosZ gene-containing microorganisms).

Funding

The Natural Science Foundation of Qinghai Province, Award: 2019-ZJ-910

The National Key Research and Development Program of China, Award: 2019YFC0507404

The International Exchange and Cooperation Project of Qinghai Province, Award: 2019-HZ-807

The Natural Science Foundation of Qinghai Province, Award: 2019-ZJ-910

The National Key Research and Development Program of China, Award: 2019YFC0507404

The International Exchange and Cooperation Project of Qinghai Province, Award: 2019-HZ-807