Greenhouse gas emissions from excreta patches of grazing animals and their mitigation strategies
Greenhouse gas emissions from excreta patches of grazing animals and their mitigation strategies
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放牧动物排泄物斑块的温室气体排放及其减缓策略
DOI：
10.1016/j.earscirev.2017.05.013
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发表时间：
2017-08-01
影响因子：
12.1
通讯作者：
Cheng, Yi
中科院分区：
文献类型：
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作者：
Cai, Yanjiang;Chang, Scott X.;Cheng, Yi
由于对畜产品的需求不断增加，全球正在饲养更多的牲畜(根据粮农组织2017年的数据，牛、绵羊、山羊和马的畜牧业从2000年的35.5亿只增加到2014年的42.4亿只)，这不可避免地导致粪便(尿液和粪便)沉积到草原上。尿液和粪便斑块是放牧草原排放的三种主要温室气体(温室气体)的热点：一氧化二氮(N2O)、甲烷(CH4)和二氧化碳(CO2)；然而，控制温室气体排放的潜在机制仍未得到很好的了解，也没有制定出减少此类温室气体排放的战略。在这里，我们回顾了关于排泄物斑块温室气体排放的研究，并提出了可能的缓解策略。排泄物斑块的N2O排放主要是由于硝化和反硝化作用的增加，伴随着氨氧化细菌(AOB)和反硝化细菌的增加。无论尿液类型如何，尿液沉积后N2O的排放量都会增加(净增量从1.06到6.51 kg N ha(-1))，而只有在牛粪沉积之后N2O的排放量才会增加(2.42+/-1.95 kg N ha(-1；平均+/-95%可信区间)，这也增加了CH4(11.8+/-5.32 kg C ha(-1))和CO2(893+/-693 kg C ha(-1))的排放。尿液对甲烷排放的影响是复杂的，还需要进一步的研究。双氰胺(DCD)的应用能有效减少黄牛尿液(-4.24+/-1.10 kg N ha(-1))和粪便(-0.66+/-0.61 kg N ha(-1))斑块的N2O排放。在尿液斑块中，DCD可以减少AOB菌群数量，但不影响反硝化细菌数量。饮食控制和放牧管理也是减少排泄物斑块温室气体排放的潜在措施。需要进一步研究，以确定生态系统一级排泄物斑块的温室气体总排放量，并探索放牧草原生态系统可持续发展的战略。
More livestock is being raised globally (increasing from 3.55 billion in 2000 to 4.24 billion in 2014 for cattle, sheep, goats and horses, based on 2017 FAO data) due to the increasing demand for livestock products, which inevitably results in increased excreta (urine and dung) deposition onto grasslands. Urine and dung patches are hotspots for emissions of the three principal greenhouse gases (GHGs): nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from grazed grasslands; however, the underlying mechanisms controlling GHG emissions are still not well understood and few strategies have been developed to mitigate such GHG emissions. Here, we review research on GHG emissions from excreta patches and propose possible mitigation strategies. The emission of N2O from excreta patches is mainly caused by increased nitrification and denitrification, in association with the increased abundance of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria. Emission of N2O increases after urine deposition regardless of the type of urine (net increases ranged from 1.06 to 6.51 kg N ha(-1)), while it increases (2.42 +/- 1.95 kg N ha(-1); mean +/- 95% confidence interval) only after cattle dung deposition, which also increases CH4 (11.8 +/- 5.32 kg C ha(-1)) and CO2 (893 +/- 693 kg C ha(-1)) emissions. The effect of urine on CH4 emission is complex and further research is required. The application of dicyandiamide (DCD) is effective in reducing N2O emissions from both cattle urine (- 4.24 +/- 1.10 kg N ha(-1)) and dung (- 0.66 +/- 0.61 kg N ha(-1)) patches. In urine patches, DCD can reduce AOB population size, but does not influence the denitrifying bacteria population size. Diet manipulation and grazing management are also potential measures for mitigating GHG emissions from excreta patches. Further research is required to ascertain the overall emission of GHGs from excreta patches at the ecosystem level and to explore strategies for the sustainable development of grazed grassland ecosystems.