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降水持续减少对元江稀树灌草丛生态系统土壤N2O排放的影响

【PDF原文: Effects of precipitation exclusion on N2O emissions in a savanna ecosystem in SW China

  N2O是一种重要的温室气体,土壤是N2O的主要来源。研究表明稀树灌草丛生态系统土壤排放的N2O约占土壤源N2O20%N2O排放速率和降雨密切相关。然而,目前对于稀树灌草丛地区N2O排放的研究多集中于雨季,且缺乏对降雨减少响应的研究。

  版纳植物园全球变化研究组博士研究生李敬在导师张一平研究员的指导下,以元江稀树灌草丛生态系统为研究对象,利用降水控制试验平台,开展了降水持续减少对土壤温室气体排放监测,探究了稀树灌草丛生态系统土壤N2O排放的基本特征及其在降水持续减少下的变化规律。研究发现:(1)稀树灌草丛生态系统土壤表现为排放N2O,排放速率与降水紧密相关,其范围为0.039~0.245 mg N m-2 day-1;(2)雨季的N2O排放速率明显高于旱季的N2O排放速率,最大N2O排放速率出现在8月,最小N2O排放速率出现在12月;(3)降水持续减少显著降低了N2O的排放,对照(CK)、减水30%PE30)、减水50%PE5)和减水70%PE7)的N2O年排放总量分别为:0.200.170.130.12 kg N ha-1 yr-1;(4)随着降水持续减少,旱季排放的N2O占比降低,雨季排放的N2O占比增加,在PE5时达到平衡;降水持续减少在旱季的抑制作用(46.38%)比雨季的抑制作用(38.04%)更为明显。研究结果表明:元江稀树灌草丛生态系统是N2O的排放源;降水持续减少将降低稀树灌草丛生态系统N2O的排放,但不能改变稀树灌草丛N2O源特征;旱季N2O排放占有重要地位,对降水减少更为敏感,应在以后的研究中予以重视,尤其是在年降水波动明显的生态系统中。

  

Abstract

Savanna ecosystems play a crucial role in global N2O emissions. However, our understanding of N2O emissions under limiting precipitation conditions is lacking. This study evaluates the effects of precipitation reduction on soil N2O fluxes from a woody savanna ecosystem in Yunnan Province, Southwest China. Precipitation exclusion shelters were installed above the tree canopy, and four total treatments were established as follows: a control (CK) and precipitation exclusions of 30% (PE3), 50% (PE5), and 70% (PE7). Two years (2015–2016) of N2O fluxes, soil temperature and soil water content data were collected. The N2O fluxes were generally low, ranging from 0.039 to 0.245 mg N m−2 day−1, and they were strongly linked to precipitation events. Additionally, the N2O fluxes during the rainy season were significantly greater than those during the dry season. The maximum N2O flux was observed in August, and the minimum flux occurred in December. Precipitation exclusion had a significant negative influence on the N2O fluxes. The N2O emissions of CK, PE3, PE5, and PE7 were 0.20, 0.17, 0.13, and 0.12 kg N ha−1 yr−1, respectively. With the exacerbation of precipitation exclusion, the decrease rate of precipitation exclusion on the N2O emissions increased over the entire year (eventually reaching 41.8% in PE7), but the decrease rate of precipitation exclusion on the soil N2O emission during the dry season was stronger than that during the rainy season. Additionally, the proportion of dry season N2O emissions to total annual emissions decreased (from 45% to 41%), and that of rainy season N2O emissions to total annual emissions increased (from 55% to 59%) over the year, whereas they exhibited a stable trend from PE5. The data show that the Yuanjiang savanna is a net source of N2O; precipitation reduction decreases the N2O emissions in the savanna regions, indicating that precipitation reduction can only slow the increase in the N2O concentration in the atmosphere and can therefore slow global warming. In addition, the N2O emissions during the dry season may play a significant role in total N2O emissions and be more sensitive to precipitation reduction than those during rainy season. These possibilities should be considered in future studies, especially in those ecosystems that experience substantial inter-annual climatic fluctuations.



相关研究结果以Effects of precipitation exclusion on N2O emissions in a savanna ecosystem in SW China为题,在线发表在Atmospheric Environment上。

  本研究得到了国家自然科学基金与云南省政府联合项目(U1602234U1202234)、国家自然科学基金青年项目(41405143)等项目的资助。此外,得到元江干热河谷生态站、公共技术服务中心和生物地球化学实验室的大力支持,在此表示衷心感谢。

【PDF原文: Effects of precipitation exclusion on N2O emissions in a savanna ecosystem in SW China

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