October 25, 2016

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Dynamic Vertical Profiles of Peat Porewater Chemistry in a Northern Peatland

Capturing current temporal, spatial variability in porewater chemistry pools sets baseline for how concentrations, pools, fluxes may change under future climate scenarios.

The Science

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.

The Impact

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.

Summary

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.

Principal Investigator

Natalie Griffiths
Oak Ridge National Laboratory
griffithsna@ornl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

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.

Related Links

References

Griffiths, N. A. and S. D. Sebestyen. "Dynamic vertical profiles of peat porewater chemistry in a northern Peatland". Wetlands 36 1119–1130  (2016). https://doi.org/10.1007/s13157-016-0829-5.