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首页> 外文期刊>Ecological Applications >Nitrous oxide nitrification and denitrification N-15 enrichment factors from Amazon forest soils
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Nitrous oxide nitrification and denitrification N-15 enrichment factors from Amazon forest soils

机译：亚马孙森林土壤中的一氧化二氮硝化反硝化N-15富集因子

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The isotopic signatures of N-15 and O-18 in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarem, ParA, and Nova Vida Farm, Rondonia. The N-15 enrichment factors for nitrification and denitrification differ with soil texture and site: -111 parts per thousand +/- 12 parts per thousand and -31 parts per thousand +/- 11 parts per thousand for a clay-rich Oxisol (TNF), -102 parts per thousand +/- 5 parts per thousand and -45 parts per thousand +/- 5 parts per thousand for a sandier Ultisol (TNF), and -10.4 parts per thousand +/- 3.5 parts per thousand (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (delta N-15(alpha) - delta N-15(beta) where alpha indicates the central nitrogen atom and beta the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2 parts per thousand +/- 8.4 parts per thousand and 31.6 parts per thousand +/- 8.1 parts per thousand, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different N-15 site preference fingerprints. Our data set strongly suggests that N2O isotopomers can be used in concert with traditional N2O stable isotope measurements as constraints to differentiate microbial N2O processes in soil and will contribute to interpretations of the isotopic site preference N2O values found in the free troposphere.
机译：热带土壤排放的N2O中N-15和O-18的同位素特征在空间和时间上都变化，从而导致整个热带源特征的不确定性很大，从而限制了同位素在限制全球N​​2O预算方面的效用。确定同位素特征时空变化的原因需要我们知道硝化和反硝化的同位素富集因子，这是在土壤中产生N2O的两个过程。我们设计了一种利用土壤温育实验测量这些富集因子的方法，并报告了该方法对巴西亚马逊河采集的三种雨林土壤的结果：三种土壤的沙子和粘土含量均来自帕拉州圣塔伦附近的塔帕霍斯国家森林（TNF）和Rondonia的Nova Vida Farm。硝化和反硝化作用的N-15富集因子随土壤质地和部位的不同而不同：对于富含粘土的Oxisol（TNF），每千份中-111份+/- 12份和-31千份+/- 11份），沙迪尔Ultisol（TNF）的-102千分之+/- 5份和-45千分之+/- 5千分，以及-10.4千分之+/- 3.5千分之（浓缩）反硝化因子）分别用于另一种Ultisol（Nova Vida）土壤。我们还表明，同位素异构体位点偏好（δN-15α-δN-15β，其中α表示N2O中的中心氮原子，β表示N2O中的末端氮原子）可能允许在生产过程和消耗过程之间进行区分N2O和N2O可以潜在地用于确定硝化作用和反硝化作用。从TNF-Ultisol培养的土壤中进行硝化和反硝化的场所偏爱分别为：千分之4.2 +/- 8.4千分和31.6千分+/- 8.1千分之三。因此，在我们的研究条件下，硝化和反硝化细菌种群表现出明显不同的N-15位点偏好指纹。我们的数据强烈表明，N2O同位素可以与传统的N2O稳定同位素测量结合使用，作为区分土壤中微生物N2O过程的约束条件，并将有助于解释在对流层中发现的同位素位点偏好N2O值。

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