The biogeochemistry of peatlands: linking nutrients, stoichiometry and greenhouse gases

我的研究计划的总体目标是在自然和干扰条件下建立土壤与环境之间的关系。我把大部分注意力集中在泥炭地上，它在加拿大覆盖了100多万平方公里，在全球碳(C)循环中发挥着重要作用，并对气候变化产生反馈。这涉及泥炭地关键过程的实地和实验室研究，并与模型的开发和应用紧密结合。许多泥炭地是在养分有效度有限的条件下发展起来的，但大气中N和P的沉积增加了，提高了养分有效度。我在这里的部分研究考察了氮磷有效性增加对泥炭地功能的影响，包括植被、水文、温室气体交换和碳封存的变化。作为生态化学计量学的一部分，植被和泥炭中碳、氮、磷和其他营养物质之间的关系至关重要。在本建议中，我概述了有助于回答这些问题的三个目标。营养物添加对全营养化沼泽功能的影响我计划继续对增加N添加进行长期研究，模拟增加的大气沉积，到Mer blue泥炭地。作为北美地区进行时间最长的泥炭地营养物添加试验，我们观察到泥炭地植物和微生物群落的变化，导致CO2汇减弱，CH4排放增加。许多变化在几年之后才出现，这凸显了长期实验的重要性。该沼泽将继续施肥至2024年，并将测量CO2交换、CH4和N2O排放，以及使用13CO2和14CO2来确定根和泥炭呼吸的比例（一名博士生）。我的工作已经确定了植物物种之间C:N:P养分维持的差异，这可能解释了它们承受营养添加的相对能力，以及加拿大森林和泥炭地的“红地比”。我将测试这些关系是否更广泛地适用，使用在不同于加拿大泥炭地条件下形成的新西兰植物和泥炭营养含量的大型数据库和深泥炭岩心（一名硕士学生）。树木沿干湿梯度的CH4排放尽管已经对土壤和大气之间CH4交换做了大量的研究，但现在有证据表明树木可能是CH4排放的重要贡献者。我建议沿着两条样带测量树干排放CH4的作用，这两条样带代表了从排水良好的泥炭土到沼泽和沼泽的泥炭土的序列，沿着梯度有常见的树种。树干和土壤表面的CH4通量将与环境变量相关，并在空间上推断，以测试我们是否需要考虑树木的作用（一名博士生）。

The overall objective of my research program is to establish the relationships between soils and the environment, under natural and disturbed conditions. I have focused much of my attention on peatlands which cover over 1 million km2 in Canada and play an important role in the global carbon (C) cycle with feedbacks to climate change. This involves field and laboratory studies of key processes in peatlands, with a strong integration with the development and application of models. Many peatlands have developed under conditions of limited nutrient availability but there have been increases in the atmospheric deposition of N and P, enhancing nutrient availability. Part of my research here examines the effect of increased N and P availability on the functioning of peatlands, including changes in vegetation, hydrology, greenhouse gas exchange and C sequestration. Critical to this are the relationships between C, N, P and other nutrients, in vegetation and peat, as part of ecological stoichiometry. In this proposal, I outline three objectives to contribute to answering these issues. The effect of nutrient addition on the functioning of an ombrotrophic bog I plan to continue a long-term study of increased N addition, simulating increased atmospheric deposition, to the Mer Bleue peatland. As the longest running peatland nutrient addition experiment in North America, we have observed changes in plant and microbial communities, resulting in a weaker CO2 sink and increases in CH4 emission. Many of the changes did not appear for several years, highlighting the importance of long-term experiments. The bog will continue to be fertilized to 2024 and measurements will be made of CO2 exchange and CH4 and N2O emissions as well as using 13CO2 and 14CO2 to determine the proportion of root and peat respiration (one PhD student). The ecological stoichiometry of peatlands My work has identified differences in C:N:P nutrient maintenance among plant species, which may explain their relative ability to withstand nutrient addition and in a `Redfield Ratio' in Canadian forests and peatlands. I will test whether these relationships are more broadly applicable, using a large data base of plant and peat nutrient content in New Zealand and deep peat cores, formed under different conditions than Canadian peatlands (one MSc student). CH4 emission by trees along dry-wet gradients Although much work has been done on exchange of CH4 between soils and the atmosphere, there is now evidence that trees can be significant contributors to CH4 emission. I propose to measure the role of tree stem emission of CH4 along two transects representing a sequence from well drained to peat soils at a bog and a swamp, with common tree species along the gradient. Fluxes of CH4 from tree stem and soil surface will be related to environmental variables and spatially extrapolated to test whether we need to take into account the role of trees (one PhD student).