Biogeochemistry and ecology of peatlands: response to global change and linking the C, N and P cycles

泥炭地的生物地球化学和生态学：对全球变化的响应以及连接碳、氮和磷循环

• 批准号: RGPIN-2014-04317
• 负责人: Moore, Tim
• 金额: $ 2.48万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=631638
• 关键词: Biogeochemistry; ecology; peatlands; response; global

Peatlands cover ~12% of the land surface of Canada, store ~100 Gt of C, emit 5 - 10 Tg CH4 /yr and are significant sources of DOC (~10 Tg/yr) to water bodies. Although we have made significant progress in measuring and modeling these fluxes, it is clear that further advances depend on a better identification of the role of nutrients, such as N and P, in influencing C cycling in peatlands, through increased atmospheric loading and through drainage and accelerated rates of mineralization. Our long-term NPK fertilization experiment at the Mer Bleue peatland has shown shrub replacement of mosses, no increase in photosynthesis despite N uptake, and increased respiration resulting in reduced C uptake or possibly loss, contrary to the expectation of fertilization. Analysis of foliar tissues shows that the Mer Bleue is N/P co-limited and responds in a conservative manner to increased fertilization. The stoichiometric cascade of C, N and P from plants through senescent leaves and litter to the peat profile shows that much of the N is conserved, resulting in a relatively narrow C:N ratio in peat and large rates of N accumulation (0.5 – 1.0 g m2/yr), yet the C:P increases as peat forms - P is drawn out of the peat (C:P 1500 to 2000:1) and maintained in the upper 0.5 m, accumulating at only 15 mg m2/yr. The peatland stoichiometry of P is very different from Canadian forest litter/soils, but the processes responsible remain unknown and this is a focus of my proposal. The sources of the large amount of N accumulated in peatlands are unknown and our estimates of N2 fixation by cyanobacteria at Mer Bleue are small compared to the accumulation rate. Our fertilization experiment provides an opportunity to test whether increasing N deposition (or P addition) affects N2 fixation rates. We shall test mosses and peat from the fertilization plots and rhizospheres for N2 fixation potential; methanotrophs are known to have N2 fixation potentials and we shall quantify this by laboratory incubations of peat profiles varying in water table position and CH4 concentration. Rates of litter and peat decomposition are important controls on peatland biogeochemistry and sources of DOC, CO2 and CH4. We are using peatland sites near Montreal, thawing permafrost in the NWT, pocosins in North Carolina and restiad bogs in New Zealand to broaden our understanding on the controls of litter and peat decomposition rates and release of N and P.

泥炭地覆盖了加拿大约 12% 的陆地表面，储存了约 100 Gt 的碳，每年排放 5 - 10 Tg CH4，并且是水体 DOC（约 10 Tg/年）的重要来源，尽管我们已经取得了重大进展。在测量和模拟这些通量时，很明显，进一步的进展取决于更好地确定养分（例如氮和磷）在影响泥炭地碳循环方面的作用，通过增加大气负荷以及通过排水和加速碳循环速率。我们在 Mer Bleue 泥炭地进行的长期 NPK 施肥实验表明，灌木取代了苔藓，尽管吸收了氮，但光合作用并未增加，呼吸作用增加，导致碳吸收减少或可能损失，这与施肥分析的预期相反。叶组织表明，Mer Bleue 是 N/P 共同限制的，并且以保守的方式响应来自 C、N 和 P 的化学计量级联的增加。通过衰老叶子和凋落物到泥炭剖面的植物观察表明，大部分氮是保守的，导致泥炭中的 C:N 比率相对较窄，氮积累率较高（0.5 – 1.0 g m2/年），但 C: P 随着泥炭的形成而增加 - P 从泥炭中排出（C:P 1500 至 2000:1）并保持在上部 0.5 m，仅累积 15 mg平方米/年。泥炭地的磷化学计量与加拿大森林凋落物/土壤有很大不同，但造成的过程仍然未知，这是我提案的重点。泥炭地中积累的大量氮的来源尚不清楚，我们的估计也是如此。与积累率相比，Mer Bleue 的蓝藻固定 N2 的速度较小。我们的施肥实验提供了一个机会来测试增加 N 沉积（或 P 添加）是否会影响 N2 固定率。施肥区和根际的泥炭具有 N2 固定潜力；众所周知，甲烷氧化菌具有 N2 固定潜力，我们将通过实验室培养不同地下水位和 CH4 浓度的泥炭剖面来量化这一点。关于泥炭地生物地球化学以及 DOC、CO2 和 CH4 的来源 我们正在使用蒙特利尔附近的泥炭地，解冻永久冻土。 NWT、北卡罗来纳州的 pocosins 和新西兰的 Restiad bogs，以拓宽我们对控制凋落物和泥炭分解速率以及氮和磷释放的理解。