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Metabolic pathways in natural systems: A tracer study of carbon isotopes.

机译：自然系统中的代谢途径：碳同位素的示踪研究。

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摘要

Anthropogenic contributions of greenhouse gasses to the atmosphere have initiated changes in environmental conditions around the world. The response of climate to these anthropogenic emissions is complex and global climate models are often used to predict future environmental conditions. Response of ecosystem-level net atmospheric flux to changing environmental conditions can be complex and is often the net result of two large opposing fluxes such as ecosystem assimilation and respiration. Bulk-flux measurements can be insufficient to resolve the two flux endmembers. The use of stable isotope tracers coupled to mass-balance equations can provide the higher resolution necessary to determine greenhouse gas flux rates and stable isotopic concentrations.;The delta13C value of foliage respiration has been considered a constant in the past and modeling efforts have assumed that the delta 13C value of foliage respiration is constant and is directly related to substrate without any fractionation. Consecutive delta13C measurements of foliage dark-respired CO2 (delta13C r) for slash pine trees (Pinus elliottii) over several diel cycles were used to test the hypothesis that significant variation in delta 13Cr would be observed. delta13Cr values collected in daylight from all time series showed mid-day 13C enrichment (5--10‰) relative to bulk biomass, but values become more 13C depleted following shading and at night and approach bulk-biomass delta 13C values by dawn. Assimilation model results suggest that respiration during daylight has the potential to significantly affect Delta13 C by as much as 1.6‰, but night dark respiration has little impact on 24-hour integrated Delta13C (0.1‰).;Net greenhouse gas flux from permafrost peatlands in the Discontinuous Permafrost Zone of northern Canada is small relative to the two larger component fluxes: carbon assimilation and methane production. These permafrost peatlands are sensitive to changes in global temperature because of the direct link between increased temperatures and permafrost thaw. Permafrost thaw will undoubtedly change the ecological conditions and alter the CO2/CH4 flux balance. We sampled methane and CO2 from collapse scar bogs (transient permafrost degradation features in permafrost peatlands) to test the hypotheses that microbial respiration and methane production are stimulated by permafrost degradation and collapse and that the fen-like vegetation (i.e. Carex and Eriophorum) found in collapse scar bogs near the collapsing edge stimulates acetate fermentation. Our results show that collapse scar bogs have an evolution of spatial variation in methanogenic pathways that is related to surface vegetation cover type. (Abstract shortened by UMI.)
机译：温室气体对大气的人为贡献已引发全球环境状况的变化。气候对这些人为排放的响应非常复杂，并且全球气候模型通常用于预测未来的环境条件。生态系统水平的净大气通量对变化的环境条件的响应可能很复杂，并且通常是两个较大的相反通量（如生态系统吸收和呼吸）的最终结果。散装通量测量可能不足以解析两个通量端部件。将稳定的同位素示踪剂与质量平衡方程式结合使用可以提供确定温室气体通量率和稳定的同位素浓度所需的更高分辨率。在过去，叶子呼吸的delta13C值被认为是恒定的，并且建模工作已假定叶子呼吸的δ13C值是恒定的，并且与底物直接相关，没有任何分馏。在几个diel周期内连续分析阔叶松树（Pinus elliottii）的叶子暗呼吸的CO2（delta13C r）的delta13C，以检验假设将观察到delta 13Cr的显着变化。白天从所有时间序列中收集到的delta13Cr值相对于整体生物量显示出中午13C富集（5--10‰），但在遮阴和夜间，其13C值消耗更多，到黎明时接近整体生​​物量δ13C值。同化模型结果表明，白天的呼吸有可能对Delta13 C产生高达1.6‰的显着影响，而夜间暗呼吸对24小时综合Delta13C的影响很小（0.1‰）。加拿大北部的不连续多年冻土带相对于两个较大的组分通量而言较小：碳同化和甲烷产生。这些多年冻土泥炭地对全球温度变化敏感，因为温度升高与多年冻土融化之间存在直接联系。多年冻土融化无疑会改变生态条件，并改变CO2 / CH4通量平衡。我们从坍塌的疤痕沼泽（多年冻土的泥炭地的瞬时多年冻土退化特征）中采样了甲烷和CO2，以检验以下假设：微生物的呼吸作用和甲烷的产生是由多年冻土的退化和塌陷刺激的，并且发现了类似fen的植被（即Carex和Eriophorum）坍塌边缘附近的疤痕沼泽塌陷会刺激醋酸盐发酵。我们的研究结果表明，坍塌的疤痕沼泽在产甲烷途径中具有与地面植被覆盖类型有关的空间变化。 （摘要由UMI缩短。）

著录项

  • 作者

    Prater, James L., Jr.;

  • 作者单位

    The Florida State University.;

  • 授予单位 The Florida State University.;
  • 学科 Biogeochemistry.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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