SGER: 13C and 15N Isotope Fractionation and Measures of Organic Matter Humification During Decomposition Across Ecosystems

SGER：13C 和 15N 同位素分馏以及跨生态系统分解过程中有机物腐殖化的测量

• 批准号: 0334793
• 负责人: Marc Kramer
• 金额: $ 7.12万
• 依托单位: University Corporation at Monterey Bay
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-15 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0334793&HistoricalAwards=false
• 关键词: SGER; 13C; 15N; Isotope; Fractionation

In a recently completed study in SE Alaska we found a strong and unexpected correlation between 15 N and aliphaticity in soils. Using Nuclear Magnet Resonance (NMR), we are developing a relatively inexpensive and simple technique for estimating humification in soils. The unusually high C content of these Alaskan mineral soils (up to 18%), we believe, facilitated obtaining reliable NMR spectra and stable isotope values. We propose here to extend this previous work to forest soil types across a broader range of climatic zones, all of which tend to be lower C content (7%) and drier than these Alaskan soils. We will determine the extent to which 15 N and 13 C values correspond to degree of soil organic matter humification (using NMR to estimate aliphaticity) in 4 contrasting ecosystems, in particular those in which illuviation is less pronounced than in the Alaskan soils, N is less limiting (open N systems), and microbial processes are faster. To do this will require exploring a variety of techniques to obtain reliable NMR spectra in the presence of paramagnetics (especially Fe). Based on the widely reported and consistent increase in 15 N values with depth (and an associated lack of consistent trend with depth reported for 13 C), our expectation is that 15 N but not 13 C values will correspond to degree of humification across ecosystems worldwide. If we successfully obtain reliable NMR spectra for the soils we study, and if this 15 N-aliphaticity pattern holds elsewhere, we will have developed a comparatively cheap proxy for degree of SOM humification, which should allow controls on this important process to be studied much more efficiently than now.

在阿拉斯加东南部最近完成的一项研究中，我们发现15n与土壤中的脂肪性之间存在强烈而意想不到的相关性。利用核磁共振（NMR），我们正在开发一种相对便宜和简单的技术来估计土壤中的腐殖化。我们认为，这些阿拉斯加矿物土壤中异常高的碳含量（高达18%）有助于获得可靠的核磁共振光谱和稳定的同位素值。在这里，我们建议将之前的工作扩展到更广泛的气候带的森林土壤类型，所有这些土壤都倾向于比阿拉斯加土壤更低的碳含量（7%）和更干燥。我们将确定4个对比生态系统中15n和13c值对应土壤有机质腐殖化程度的程度（使用核磁共振来估计脂肪化），特别是那些光照不如阿拉斯加土壤明显、N限制较少（开放N系统）和微生物过程更快的生态系统。要做到这一点，需要探索各种技术，以在顺磁性（特别是铁）存在的情况下获得可靠的核磁共振光谱。根据广泛报道的15 N值随深度的持续增加（以及相关的13 C缺乏与深度一致的趋势），我们的预期是15 N值而不是13 C值将对应于全球生态系统的腐殖化程度。如果我们成功地为我们研究的土壤获得可靠的核磁共振光谱，并且如果这种15 n -脂肪化模式在其他地方成立，我们将开发出一种相对便宜的SOM腐殖化程度的代理，这应该允许对这一重要过程的控制进行比现在更有效的研究。