Fine-scaled spatiotemporal variability of surface elevation change in a northern peatland: Interactions with hydrology and vegetation
Abstract
The depth of the groundwater table below the surface (GWT) is a major control on biogeochemical processes in northern peatlands. In these wetlands, the fluctuations in GWT are stabilized by expansion and compression of the organic soil (peat) matrix (peat volume change; ΔPV). It is unclear at which spatial scale this feedback occurs and which processes control its spatial variability. We explored the fine-scale (0.5 m resolution) spatial structure of ΔPV and its relationship to vegetation and hydrology using spatially continuous data of surface elevation and point measurements on plant species composition, geohydrological, and positional factors along a transect in a northern peatland throughout a growing season. We found that ΔPV ranged between -6 cm and +1.2 cm over the growing season, showing large spatial variation. Spatial patterns of ΔPV over the whole season emerged at a spatial scale of 40.8 ± 0.6 m (± SE). Over the growing season, with progressively deeper absolute groundwater tables, peat volume change increased heterogeneity of peat surface elevation, and elevation differences became more pronounced. Spatial variation in ΔPV was mainly related to changes in aquifer thickness, and to a lesser extent also to larger vegetation units (microsites), with magnitude of ΔPV increasing from moist lawn < wet hollow < wet flark. Our results show that ΔPV can be substantial and is highly spatially variable. As a consequence of the high spatial variability, the spatial representativeness of point scale simulation models including ΔPV is restricted to a range up to about 40 m. This study provides empirical evidence of a link between large scale vegetation units and peat volume change, one of the mechanisms hypothesised to play an important role in hydrological self-regulation in northern peatlands.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2018
- Bibcode:
- 2018EGUGA..2016926N