Stimulation of soil gross nitrogen transformations and nitrous oxide emission under Free air CO2 enrichment in a mature temperate oak forest at BIFoR-FACE
Stimulation of soil gross nitrogen transformations and nitrous oxide emission under Free air CO2 enrichment in a mature temperate oak forest at BIFoR-FACE
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BIFoR-FACE 成熟温带橡树林在自由空气 CO2 富集下对土壤总氮转化和一氧化二氮排放的刺激
DOI：
10.1016/j.soilbio.2023.109072
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发表时间：
2023
影响因子：
9.7
通讯作者：
Ullah, Sami
中科院分区：
文献类型：
--
作者：
Sgouridis, Fotis;Reay, Michaela;Cotchim, Suparat;Ma, Jiaojiao;Radu, Aleksandar;Ullah, Sami
森林生态系统被认为是全球重要的吸收汇，可以抵消人为增加的大气二氧化碳（CO2），但是，这可能受到土壤养分供应的限制，主要是氮和磷。不确定性仍然是关于如何在成熟的森林土壤氮循环可能会对碳供应量的变化作出反应，由于缺乏实验数据，在CO2浓度升高（eCO 2）下增强光合作用。此外，一氧化二氮排放的潜在正反馈可能抵消eCO 2下额外固碳的好处。伯明翰森林研究所的自由空气碳富集实验（BIFoR-FACE）于2017年开始以高于环境的+150 ppm CO2熏蒸成熟的温带落叶林。采用15 N池稀释法研究了2018 - 2020年（熏蒸第2 - 4年）土壤氮素循环对eCO 2的响应，以评估总氮矿化、固定和硝化速率，并结合15 N气体通量法对N2 O产生进行量化和源分区。与对照处理（5.3 μg N g−1d−1）相比，eCO 2（6.6 μg N g − 1d − 1）下的土壤总氮矿化增加了20%，尽管三年（2018-2020）的趋势一致，但阵列之间的高变异性降低了统计学显著性，2019年除外。在eCO 2（3.5 μg N g−1d−1）下，微生物对铵的固定也增加了20%。总体而言，总矿化比硝化高4倍，表明铵周转率比硝酸盐高得多（1.5天与12天平均停留时间）。反硝化作用产生的N2 O排放量（0.18 ng N g−1h−1）在eCO 2下显著较高。经过四年的CO2熏蒸，有适度的迹象表明，增强土壤氮转化率和氮的可用性，以支持所观察到的增强冠层CO2吸收。eCO 2下N2 O通量的增加表明，在大气CO2上升的情况下，碳封存有可能产生正反馈。碳封存的总体影响将取决于多久上调土壤氮转化和氮的生物利用度将持续满足植物的需求之前，表现出的氮限制，如果有的话。
Forest ecosystems are considered globally important sinks for offsetting increasing anthropogenic atmospheric carbon dioxide (CO2), however, this may be limited by the soil nutrient supply, predominantly nitrogen and phosphorus. Uncertainty remains regarding how soil N cycling in mature forests may respond to changes in carbon availability, arising from enhanced photosynthesis under elevated CO2(eCO2) due to lack of experimental data. Further, potential positive feedbacks of nitrous oxide emissions may offset benefits of additional carbon sequestration under eCO2. The Birmingham Institute of Forest Research Free Air Carbon Enrichment experiment (BIFoR-FACE) started fumigating a mature temperate deciduous forest in 2017 at +150 ppm CO2above ambient. Soil N cycling responses to eCO2were investigated using the15N pool dilution approaches to assess gross N mineralisation, immobilisation and nitrification rates, in combination with the15N-gas flux method to quantify and source partition N2O production from 2018 to 2020 (2nd to 4th year of fumigation). Soil gross N mineralisation increased by 20% under eCO2(6.6 μg N g−1d−1) compared to the control treatment (5.3 μg N g−1d−1) and despite the trends being consistent over the three years (2018–2020), the high variability between arrays reduced statistical significance except in 2019. Ammonium immobilisation by microbes increased by 20% under eCO2(3.5 μg N g−1d−1) as well. Overall, gross mineralisation was 4 times higher than nitrification, indicating a much higher ammonium turnover rate compared to nitrate (1.5 vs. 12 days mean residence time). N2O emission from denitrification (0.18 ng N g−1h−1) was significantly higher under eCO2. After four years of CO2fumigation, there are modest indications of enhanced soil N transformation rates and N availability to support the observed enhanced canopy CO2uptake. Increased N2O fluxes under eCO2indicated the potential for positive feedbacks on C sequestration under rising atmospheric CO2. The overall implications for C sequestration will depend on how long upregulation of soil N transformations and N bioavailability will last to meet plant demands before manifestation of N limitation, if any.