Microclimatic Effects of a Perched Peatland Forest Gap

Abstract

We use a canopy-resolving regional atmospheric–forest large-eddy simulation to investigate the impact of fetch on flow separation and microclimates within a peatland surrounded by a forest (representing a forest gap). We initiate our simulation with observed vegetation characteristics and meteorological data within a peatland and a forest to accurately estimate the natural surface roughness and energy dynamics. The heterogeneous landscape of the Boreal Plains region results in peatlands often experiencing turbulent sheltering and turbulent effects from their surrounding ecosystems. This landscape configuration results in spatially dynamic surface–atmosphere exchanges of momentum, heat, and moisture, produced by flow-separation dynamics within the peatland that regulate the transport of such scalars in the sheltered region while promoting transport in the reattachment zone. Peatlands of the Boreal Plains are often small irregular shapes, which add further complexity when estimating the transport of scalars within these systems. As evapotranspiration is the dominant hydrologic flux in Boreal Plains, it is necessary to understand the dynamics and controls on evapotranspiration within these fetch-limited peatlands. Our simulations show that fetch limitations have no impact on the turbulent and evaporative dynamics of the peatland relative to the distance from the surface transition. However, we observe that a combination of peatland geometry (i.e., the ratio of peatland length to width) and/or the shape of the exit transition influences the flow region where greater funnelling of the flow of the peatland increases the regional wind speeds.