Microclimatic Effects of Forest to Peatland Transitions Within the Boreal Plains

peatland;flow separation;hydrometeorology

Green, Adamadvisor:Petrone, Richard ; affiliation1:Faculty of Environment ; Petrone, Richard ;

University of Waterloo

关键词: flow separation;    Master Thesis;    peatland;    hydrometeorology;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/14605/3/Green_Adam.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Peatlands cover approximately 50% of the total landscape of the Western Boreal Forest, whichincludes the sub-humid Boreal Plains (BP) ecozone. The BP experiences persistent water deficitconditions, promoting anaerobic conditions, which has the potential to increase decomposition,transforming the peatlands from carbon sinks to carbon sources. With evapotranspiration (ET)being the dominant source of water loss in the BP, peatland persistence is hydrologicallyprecarious, and as such, it is necessary to understand the dynamics and controls on ET within thesesystems. Due to the heterogeneity of the landscape, surrounding upland forests often shelterpeatlands from wind. This results in spatially varying evaporative rates, which can influencesurface moisture and vegetation regimes across a peatlands surface. High-resolution turbulentmodels allow for such flow scenarios to be resolved as they resolve flow in a 3D domain.Therefore, high-resolution turbulent models are essential in assessing the spatial variability ofstresses placed on surface scalars such as ET, by displacement height transition.This study uses a canopy resolving large-eddy simulation (RAFLES) to study the impactof displacement height transitions on surface-atmosphere exchanges of moisture within peatlandsof the BP. The dimensions, vegetation structure and energy dynamics of the modeled peatlandswere generated from observations of natural peatlands of the BP. Within the sheltered regionleeward of a backward-facing step transition, the simulated peatlands experienced higherresistances to surface-atmosphere exchanges of moisture when compared to the reattachment andrecovery regions. However, this trend was muted when the surface roughness of the peatland wasincreased as the roughness lowered the overall resistance of the surface. This study also found thatthe length of the peatland did not influence the flow reattachment dynamics within the peatland.However, it was observed that the peatlands with a narrow shape and a curved front-facing stepgeometry resulted in faster regional wind velocities. Understanding the turbulent dynamics withinheterogeneous landscapes can help to control the rate and variability of surface to atmosphereexchanges of moisture within disrupted and reclaimed landscapes which can increase thepredictability of moisture demands within future landscapes.