N2O emissions and product ratios of nitrification and denitrification as affected by freezing and thawing
N2O emissions and product ratios of nitrification and denitrification as affected by freezing and thawing
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DOI：
10.1016/j.soilbio.2006.05.015
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发表时间：
2006-12-01
影响因子：
9.7
通讯作者：
Bakken, Lars Reier
中科院分区：
文献类型：
--
作者：
Morkved, Pal Tore;Dorsch, Peter;Bakken, Lars Reier
农业土壤对大气中的一氧化二氮（N2 O）有很大贡献。年N2 O排放的相当一部分可能发生在寒冷的季节，可能是由反硝化（N2 O/（N-2 + N2 O））和硝化（N2 O-N/（NO3--N + NO2--N））在低温和/或响应冻融扰动的高产品比率的支持。对霜冻敏感的渔获作物和绿色肥料释放的水溶性有机物质可能进一步增加冬季排放。我们进行了短期的实验室培养下，标准化的水分和氧气（O-2）的条件下，使用氮（N）示踪剂（N-15），以确定过程速率和排放的N2 O的来源后，土壤冻融处理后，或加入冻融提取物后，从三叶草。土壤呼吸和N2 O的产生刺激冻融或添加植物提取物。N2 O排放响应呈负相关的O-2浓度，反硝化作为定量占主导地位的过程。在两个研究土壤（pH 4.5和7.0）的反硝化产物的比例仍然基本不变的冻融或冻融释放的植物材料，驳斥了假设，冬季排放量高是由于霜冻破坏的N2 O还原酶活性。当O-2浓度高于2.3vol%时，冻融处理土壤中NOD库富集量估算的硝化速率为1.5-1.8 μ g NO3-N g（-1）dw土壤d（-1），当O-2浓度为0.8vol%时，硝化速率降低一个数量级。因此，实验捕获了严重的O-2限制硝化的情况。正如预期的那样，0.8体积%的O-2胁迫导致高硝化产物比率（0.3 g g（-1））。尽管有这种高的产物比，但仅4.4%的测得的N2 O积累源自硝化作用，这再次证实了在冻融影响的土壤中，在各种测试的O2浓度下，反硝化作用是主要的N2 O源。N2 O排放响应冻融和植物提取物的加入似乎与碳（C）呼吸的刺激密切相关，这表明冻融诱导的可分解有机C的释放是我们土壤中N2 O排放的主要驱动力，既通过燃料发酵剂，也通过消耗O-2。可溶性C（作为植物提取物施用）诱导与冻融相当的CO2和N2 O产生速率所必需的是20-30 pg C g（-1）土壤dw。这在文献报道的捕捞作物和绿色粪肥地块越冬可溶性碳损失的估计范围内。因此，冻融释放的有机C从植物可能发挥重要作用，冻融相关的N2 O排放。(c)2006爱思唯尔有限公司保留所有权利。
Agricultural soils contribute significantly to atmospheric nitrous oxide (N2O). A considerable part of the annual N2O emission may occur during the cold season, possibly supported by high product ratios in denitrification (N2O/(N-2 + N2O)) and nitrification (N2O-N/ (NO3--N + NO2--N)) at low temperatures and/or in response to freeze-thaw perturbation. Water-soluble organic materials released from frost-sensitive catch crops and green manure may further increase winter emissions. We conducted short-term laboratory incubations under standardized moisture and oxygen (O-2) Conditions, using nitrogen (N) tracers (N-15) to determine process rates and sources of emitted N2O after freeze-thaw treatment of soil or after addition of freeze-thaw extract from clover. Soil respiration and N2O production was stimulated by freeze-thaw or addition of plant extract. The N2O emission response was inversely related to O-2 concentration, indicating denitrification as the quantitatively prevailing process. Denitrification product ratios in the two studied soils (pH 4.5 and 7.0) remained largely unaltered by freeze-thaw or freeze thaw-released plant material, refuting the hypothesis that high winter emissions are due to frost damage of N2O reductase activity. Nitrification rates estimated by nitrate (NOD pool enrichment were 1.5-1.8 mu g NO3-N g(-1) dw soil d(-1) in freeze-thaw-treated soil when incubated at O-2 concentrations above 2.3vol% and one order of magnitude lower at 0.8 vol% O-2. Thus, the experiments captured a situation with severely O-2-limited nitrification. As expected, the O-2 stress at 0.8 vol% resulted in a high nitrification product ratio (0.3 g g(-1)). Despite this high product ratio, only 4.4% of the measured N2O accumulation originated from nitrification, reaffirming that denitrification was the main N2O source at the various tested 02 concentrations in freeze-thaw-affected soil. N2O emission response to both freeze-thaw and plant extract addition appeared strongly linked to stimulation of carbon (C) respiration, suggesting that freeze-thaw-induced release of decomposable organic C was the major driving force for N2O emissions in our soils, both by fuelling denitrifiers and by depleting O-2. The soluble C (applied as plant extract) necessary to induce a CO2 and N2O production rate comparable with that of freeze-thaw was 20-30 pg C g(-1) soil dw. This is in the range of estimates for over-winter soluble C loss from catch crops and green manure plots reported in the literature. Thus, freeze-thaw-released organic C from plants may play a significant role in freeze-thaw-related N2O emissions. (c) 2006 Elsevier Ltd. All rights reserved.