24 October 2016
Capturing temporal and spatial variability in porewater chemistry under current conditions establishes a baseline for considering how concentrations, pools, and fluxes may change under future climate scenarios.
Researchers examined weekly to monthly variation in peat porewater chemistry [pH, cations, nutrients, and total organic carbon (TOC)] depth profiles in an experimental bog in northern Minnesota and compared this temporal variation to spatial (among plot) variation in chemistry.
These data provide baseline information on porewater chemistry in the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) experimental bog, highlighting the importance of collecting samples across both space and time. Capturing temporal and spatial variability is needed especially for solute pool and flux calculations and for parameterizing process-based models.
Research findings showed strong gradients in chemistry depth profiles. For example, ammonium increased and TOC decreased with depth, likely reflecting mineralization of deep peat or TOC. These depth profiles were also temporally dynamic, with ammonium, soluble reactive phosphorus, and potassium concentrations more temporally variable in near-surface porewater than deeper porewater; pH, calcium, and TOC concentrations were more temporally variable at deeper depths. When temporal variation in porewater chemistry at one location was compared to spatial variation in porewater chemistry across 17 locations (SPRUCE plots), findings showed that temporal variation in chemistry at one location was often greater than spatial variation in chemistry, especially in near-surface porewater. These results suggest that representative sampling of porewater requires measurements across both space and time.
BER Program Managers
Daniel Stover and Jared DeForest
Oak Ridge National Laboratory
Oak Ridge, TN 37831
This research was part of the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) project and supported by the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, and the Northern Research Station of the U.S. Department of Agriculture’s Forest Service.
Griffiths, N.A., and S.D. Sebestyen. “Dynamic vertical profiles of peat porewater chemistry in a northern Peatland.” Wetlands 36, 1119–30 (2016). [DOI:10.1007/s13157-016-0829-5]
ORNL TES SFA (SPRUCE) and the Northern Research Station of the USDA Forest Service.