Rye cover crop incorporation and high watertable mitigate greenhouse gas emissions in cultivated peatland
Rye cover crop incorporation and high watertable mitigate greenhouse gas emissions in cultivated peatland
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DOI：
10.1002/ldr.3390
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发表时间：
2019-07
影响因子：
4.7
通讯作者：
Yuan Wen;H. Zang;B. Freeman;Qingxu Ma;D. Chadwick;Davey L. Jones
中科院分区：
文献类型：
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作者：
Yuan Wen;H. Zang;B. Freeman;Qingxu Ma;D. Chadwick;Davey L. Jones
泥炭土的排水和耕作几乎总是导致土壤迅速退化和土壤有机质（SOM）的损失。冬季覆盖作物种植以及随后的施肥和地下水位升高被认为是改善土壤质量和减少排水和开垦泥炭地养分损失的潜在策略。然而，剩余物掺入和地下水位管理对这些高产泥炭土温室气体排放的综合影响尚不清楚。在本研究中，在两个地下水位深度（- 50和- 30 cm），将两种碳氮比差异较大的冬季覆盖作物（紫薇[Vicia sativa]， 45-60；黑麦[Secale cereale]， 13-14）作为绿肥（不额外添加合成/有机氮）施用于泥炭土中。我们的研究结果表明，在有利的环境条件下，结合残留物的快速矿化可以引起大脉冲的温室气体释放。与裸地处理相比，施用紫薇和黑麦都增加了二氧化碳排放量，这是由于添加了不稳定的碳和消除了氮的限制。然而，两种覆盖作物对N2O排放的影响差异很大。与裸地处理相比，低碳氮比的紫薇处理促进了N2O排放（平均21.8±7.3 mg N m−2 hr−1），而高碳氮比的黑麦处理减少了N2O排放（平均0.09±0.03 mg N m−2 hr−1）。提高地下水位通过抑制SOM矿化，使CO2排放量从平均1.3±0.4（裸土）略微降低到0.9±0.3 g C m−2 hr−1，但通过刺激反硝化作用，使N2O排放量显著增加。CH4通量不受地下水位的影响，其对全球变暖总潜势的贡献可以忽略不计。因此，我们得出结论，高碳氮比覆盖作物（如黑麦）与提高地下水位相结合可能是减少沼泽泥炭土壤温室气体通量的可行管理选择。
Drainage and cultivation of peat soils almost always result in rapid soil degradation and a loss of soil organic matter (SOM). Winter cover crop cultivation and subsequent incorporation and watertable elevation have been considered as potential strategies to improve soil quality and decrease nutrient loss in drained and cultivated peatlands. However, the combined effect of residue incorporation and watertable management on greenhouse gas (GHG) emissions in these highly productive fen peat soils remains unknown. In the present study, two winter cover crops with contrasting carbon/nitrogen ratios (vetch [Vicia sativa], 45–60; rye [Secale cereale], 13–14) were incorporated into peat soils as green manure (without extra synthetic/organic N addition) at two watertable depths (−50 and −30 cm). Our results showed that fast mineralization of incorporated residues can cause a large pulse of GHG release under favourable environmental conditions. Both vetch and rye incorporation increased CO2 emissions compared with the bare soil treatments due to labile C addition and removal of N constraints. However, the two cover crops had strongly contrasting effects on N2O emissions. Incorporation of low C/N ratio vetch stimulated N2O emissions (average 21.8 ± 7.3 mg N m−2 hr−1) compared with the bare soil treatments, whereas high C/N ratio rye decreased N2O emissions (average 0.09 ± 0.03 mg N m−2 hr−1). Raising the watertable slightly reduced CO2 emissions from an average of 1.3 ± 0.4 (the bare soils) to 0.9 ± 0.3 g C m−2 hr−1 by inhibiting SOM mineralization but significantly increased N2O emissions in the vetch treatments by stimulating denitrification. CH4 fluxes were not affected by watertable depth, and their contribution to total global warming potential was negligible. Therefore, we conclude that high C/N ratio cover crops (e.g., rye) in combination with a raised watertable may represent a viable management option to mitigate GHG fluxes in fen peat soils.