RUI: Carbon Accumulation in the Fens of Boreal, Western Canada

寒带和亚北极泥炭地生态系统覆盖了地球陆地表面的3- 4%，并以泥炭的形式储存了世界上约1/3的土壤C。泥炭地代表着一个主要的全球碳库，但目前尚不清楚它们在今天和未来是作为大气碳的来源还是汇。根据最近对加拿大北部西部（阿尔伯塔省、萨斯喀彻温省和马尼托巴省）泥炭地的调查，泥炭地生态系统总共覆盖了365,157平方公里的陆地表面，并以泥炭的形式储存了42 Pg （10 15 g）的碳。以前的研究，包括我们自己的研究，主要集中在加拿大北部西部的大陆沼泽，永久冻土沼泽和内部草坪（最近永久冻土融化的地区）泥炭地特征，但我们现在知道，三分之二的泥炭地面积和碳储量不在这些类型的系统中，而是在沼泽中，泥炭地在水文上与地表水和地下水系统相连。我们建议使用我们用于研究加拿大北部西部沼泽的方法来比较加拿大北部西部大陆沼泽，贫穷沼泽和富裕沼泽之间的碳积累和碳循环。我们将解决三个具体目标：1)通过取心、210pb测年和建模来描述和比较最近的碳积累；2)量化苔藓生成分解速率和气态碳通量；3)通过取心、宏观化石分析、14C测年和模拟来表征碳积累的长期历史发展。结果将检验一个整体的工作假设，即大陆沼泽的净碳积累量大于贫穷或富裕的沼泽。沼泽中的高积累归因于褐藻对分解的抵抗力，尽管沼泽中有相对较厚的好氧acrotelm（上层、好氧、不饱和泥炭层）。虽然贫沼和富沼也会积累碳，但它们积累碳的速度相对较慢——泥炭沼和褐色苔藓在接近地表的地方分解相对较快，但由于地下水位较高，表层很薄。正是薄的胞膜促进了沼泽中碳的积累。C积累速率的差异更多地是由分解的差异而不是NPP的差异决定的。这项研究的发现将改善我们对加拿大西部北部泥炭地生态系统是否代表大气二氧化碳净汇的程度的估计。

Boreal and subarctic peatland ecosystems cover about 3-4 % of the earth's land surface and store about 1/3 of the world's soil C as peat. Peatlands represent a major global C pool, yet it is unclear whether they function as sources or sinks of atmospheric C, both today and into the future. Based on a recent inventory of peatlands in boreal western Canada (Alberta, Saskatchewan, and Manitoba), peatland ecosystems collectively cover 365,157 km 1 of the land surface and store 42 Pg (10 15 g) of C as peat. Previous research, including our own, has focused on continental bog, permafrost bog, and internal lawn (areas of recent permafrost melt) peatland features in boreal western Canada, but we now know that 2/3 of the peatland area and C storage are not in these types of systems, but rather are in fens, peatlands hydrologically connected to surface water and groundwater systems. We propose to use approaches that we have used to study bogs in boreal western Canada to compare carbon accumulation and carbon cycling between continental bogs, poor fens and rich fens of boreal western Canada.We will address three specific objectives: 1) to characterize and compare recent C accumulation through coring, 210Pb-dating and modeling; 2) to quantify moss production and decomposition rates and gaseous C fluxes, and 3) to characterize the long-term historical development of C accumulation through coring, macrofossil analysis, 14C dating and modeling. Results will test an overall working hypothesis that net C accumulation is greater in continental bogs than in poor or rich fens. High accumulation in bogs is attributed to the resistance of Sphagnum fuscum to decomposition, despite a relatively thick aerobic acrotelm (upper, aerobic, non-saturated peat layer) in bogs. Although poor fens and rich fens also accumulate C, they do so at comparatively lesser rates - fen Sphagnum and brown mosses decompose comparatively rapidly very near the surface, but because of high water table positions, the acrotelm is thin. It is the thin acrotelm that promotes C accumulation in fens. Differences in C accumulation rates are determined more by differences in decomposition than by differences in NPP. Findings from this research will improve our estimate of the extent to which peatland ecosystems of boreal western Canada do or do not represent a net sink for atmospheric CO2.