The Effects of Trees on Peatland Evapotranspiration Across Scales

加拿大的西部北方平原（WBP）提供重要的生态系统服务，如水和碳储存，也是加拿大经济引擎的重要组成部分，通过其资源型工业（采矿、林业、石油和天然气），其中最重要的是油砂开发区。在WBP普遍干燥的气候中，水的可用性是有限的，使得主导该地区的泥炭地容易受到气候变化的影响，以及来自影响泥炭地生态和水文功能的强烈工业压力的压力。了解内部和外部的生态水文和气候过程，使泥炭地生态系统有效地利用现有的水分是重要的管理这些系统的气候和土地利用变化。文献表明，碳，能量和水的交换可以强烈影响外部的局部边界层条件，除了内部的生物物理控制。然而，很少有工作已经做了泥炭地一般和大部分的研究，迄今为止，集中在沼泽生态系统，而不是沼泽在这个气候脆弱的地区。从内部看，地表覆盖变化，特别是树木密度、土壤条件和蒸散量损失之间存在反馈。从外部看，湿地和林地的景观镶嵌图表明，泥炭地不仅为森林高地提供了水源，而且森林高地还保护了泥炭地，限制了蒸发损失。了解泥炭地如何保护自己免受水分胁迫的机制将提高我们对这些系统如何应对气候变化的预测能力，并使我们能够设计出更强大和更有弹性的再生系统。 这项研究的总体目标是研究如何在这种干燥的气候中，泥炭地和森林协同作用，以克服可用水分少，干旱期延长和广泛的土地利用干扰的障碍，景观发展战略的可持续性。本研究将研究水利用效率（WUE），以探索这些协同作用（过程）以及它们如何在不同尺度上运作。以下具体目标将得到解决：（1）量化的小规模（内）泥炭地生态水文反馈之间的表面能量和质量通量沿着梯度的树木覆盖和干扰;（2）评估大规模的景观相互作用，地面形态和树木密度/高度和森林高地的方向（方面和风向）影响泥炭地蒸散。这项研究将解决上述知识差距，并改进模型，以预测该地区对气候变暖和人类干扰的反应，对政策和管理具有重要意义。

The Western Boreal Plain (WBP) of Canada, provides important ecosystem services such as water and carbon storage and also represents a substantial component of Canada's economic engine through its resource-based industries (mineral mining, forestry, oil and gas), the most significant of which is the oil sands development region. In the generally dry climate of the WBP, water availability is limited, making the peatlands that dominate this region vulnerable to climate variability as well as stresses from intense industrial pressures that affect peatland ecological and hydrological functioning. Understanding the internal and external ecohydrological and climatological processes that permit peatland ecosystems to efficiently use available moisture is important for managing these systems in light of climate and landuse change. The literature suggests that carbon, energy and water exchange can be strongly influenced by external local boundary layer conditions in addition to internal biophysical controls. However, little work has been done on peatlands in general and much of the research thus far has focused on bog ecosystems rather than fens in this climatically tenuous region. Internally, feedbacks exist between changes in surface cover, particularly tree density, soil conditions and evapotranspiration losses. Externally, the landscape mosaic of wetlands and forestlands suggests that not only do peatlands provide water to forested uplands, but that the forested uplands shelter peatlands, limiting evaporative losses. Understanding the mechanism of how peatlands protect themselves against moisture stress will refine our predictive capacity of how these systems will respond to climate change, as well as permit us to design more robust and resilient reclaimed systems. The overall goal of this research is to examine how the landscape has developed strategies for sustainability in this dry climate where peatlands and forests interact synergistically to overcome the barrier of little available moisture, prolonged drought periods and extensive landuse disturbance. This research will examine water use efficiency (WUE) to explore these synergistic interactions (processes) and how they operate at different scales. The following specific objectives will be addressed: (1) quantifying the small-scale (within) peatland ecohydrological feedbacks among surface energy and mass fluxes along a gradients in tree cover and disturbance; and (2) assessing large-scale landscape interactions, where ground surface morphometry and tree density/height and orientation of forested uplands (with respect to aspect and wind direction) influence peatland evapotranspiration. This research will address the above knowledge gap and improve models for predicting the response of this region to climate warming and human disturbance at scales of importance to policy and management.