摘要
Increasing nitrogen(N)input has been recognized as one of the important factors influencing methane(CH_(4))uptake and nitrous oxide(N_(2)O)emission in arid and semiarid grasslands.Numerous studies have examined the spatiotemporal variations of CH_(4)and N_(2)O fluxes in various ecosystems;however,the variation of the interplay between CH_(4)uptake and N_(2)O emission with increasing N has not yet been well understood.This study explored the relationship between CH_(4)uptake and N_(2)O emission in a semiarid grassland in Inner Mongolia,northern China,under a gradient of 12-year N additions.We found a synergistic relationship at low-N levels,where CH_(4)uptake and N_(2)O emission are positively correlated.Conversely,an antagonistic interaction emerged with a negative correlation between CH_(4)uptake and N_(2)O emission observed at high-N levels,which was evidenced by a 33.62%decrease in CH_(4)uptake and a 264.91%increase in N_(2)O emission.Further independent analysis,covering at least five N addition levels across grassland ecosystems in China,confirmed the general pattern:three of four cases showed a synergistic relationship at low-N levels and an antagonistic relationship at high-N levels.Given the increasing N deposition in the future,the dynamics between CH_(4)uptake and N_(2)O emission are critical for understanding the impact of external N input on net greenhouse gas emission and consequent global climate change.
氮(N)输入增加是影响干旱和半干旱草地甲烷(CH_(4))吸收和氧化亚氮(N_(2)O)排放的重要因素之一。已有大量研究探讨了不同生态系统中CH_(4)和N_(2)O通量的时空变化,但尚不清楚CH_(4)吸收和N_(2)O排放之间的耦合关系随着N输入的增加如何变化。本研究依托中国北部内蒙古半干旱草原地区开展了连续12年的N添加实验平台,探讨CH_(4)吸收与N_(2)O排放之间的耦合关系。研究结果表明,CH_(4)吸收和N_(2)O排放在低N添加条件下呈现正相关的协同关系;在高N添加条件下,呈现负相关的拮抗关系,具体表现为CH_(4)吸收减少了33.6%,N_(2)O排放增加了264.9%。中国草地生态系统至少5个N添加水平实验的独立分析证实了这一普遍规律:4个N添加实验中,有3个在低N水平上表现出协同关系,在高N水平上表现出拮抗关系。考虑到未来N沉降会增加,本研究中观察到的CH_(4)吸收与N_(2)O排放之间耦合关系的变化对于理解外源N输入对温室气体净排放及其对全球气候变化的影响至关重要。
基金
supported by the National Natural Science Foundation of China(32271681)
by Key Laboratory of Ecology and Environment in Minority Areas(Minzu University of China),National Ethnic Affairs Commission(KLEEMA202206).
