Livestock-induced N2O emissions may limit the benefits of converting cropland to grazed grassland as a greenhouse gas mitigation strategy for agricultural peatlands
Livestock-induced N2O emissions may limit the benefits of converting cropland to grazed grassland as a greenhouse gas mitigation strategy for agricultural peatlands
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DOI：
10.1016/j.resconrec.2021.105764
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发表时间：
2021-11
影响因子：
13.2
通讯作者：
Yuan Wen;B. Freeman;D. Hunt;S. Musarika;H. Zang;K. Marsden;C. Evans;D. Chadwick;Davey L. Jones
中科院分区：
文献类型：
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作者：
Yuan Wen;B. Freeman;D. Hunt;S. Musarika;H. Zang;K. Marsden;C. Evans;D. Chadwick;Davey L. Jones
排干的泥炭地支持着高利润的农业，但也是全球重要的温室气体排放源。草地通常可以保持比农田更高的水位，因此将农田转化为草地是一种潜在的二氧化碳减排战略，可以继续进行农业生产。然而，草原上高水位和牲畜的存在有产生大量一氧化二氮排放的风险，特别是与牲畜尿斑有关。通过中尺度控制试验，定量研究了地下水位（10 cm、30 cm和50 cm地下水位）和绵羊尿沉降对泥炭土温室气体排放的交互影响。我们的研究结果表明，由于有利于硝化和不完全反硝化相互作用的条件，尿处理和对照的中生态系统在30 cm处的N2O排放量都明显更高。尿N2O排放因子在WTD 30 cm时为0.25±0.17%，在WTD 50 cm时为0.20±0.07%，低于草地典型值。生态系统呼吸和甲烷通量在30 cm和50 cm湿地间无显著差异。总体而言，我们得出结论，通过将农田转化为草地来提高排水泥炭地水位的策略需要考虑到N2O排放的潜在影响，同时寻求最大限度地减少总体温室气体排放。为缓解气候变化而将泥炭地从农田管理转向草地管理，还需要考虑牲畜甲烷排放的影响，以及其他地方作物生产对土地需求增加所造成的替代排放。
Drained peatlands support highly profitable agriculture, but also represent a globally important source of greenhouse gas (GHG) emissions. Grasslands can typically be maintained at higher water levels than croplands, so conversion of cropland to grassland represents a potential CO2mitigation strategy that allows for continued agricultural production. However, the presence of high water levels and livestock on grasslands risks generating high emissions of N2O, particularly associated with livestock urine patches. In the present study, a controlled mesocosm experiment was carried out to quantify the interactive impacts of groundwater level (10 cm, 30 cm and 50 cm water table depth, WTD) and sheep urine deposition on GHG emissions from peat soils. Our results showed that N2O emissions were significantly higher at 30 cm for both urine-treated and control mesocosms, due to the conditions favouring the interplay of nitrification and incomplete denitrification. The urine N2O emission factor was 0.25±0.17% at the 30 cm WTD and 0.20±0.07% at 50 cm WTD, lower than typical values for grasslands. No significant difference was observed in ecosystem respiration or methane flux between 30 cm and 50 cm WTDs. Overall, we conclude that strategies to raise water levels in drained peatlands through conversion of cropland to grassland need to account for the potential impacts of N2O emissions when seeking to minimise overall GHG emissions. Shifting from cropland to grassland management on peatlands for climate change mitigation also requires consideration of the effects of livestock methane emissions, and displaced emissions resulting from increased land demand for crop production elsewhere.