Fluxes project at North Temperate Lakes LTER: Predicting Peat Depth in a North Temperate Lake District 2008

Peat deposits contain on the order of 1/6 of the Earth's terrestrial fixed carbon (C),
but uncertainty in peat depth precludes precise estimates of peat C storage. To assess peat
C in the Northern Highlands Lake District (NHLD), a approximately 7000 square km region in
northern Wisconsin, United States, with 20 percent peatland by area, we sampled 21
peatlands. In each peatland, peat depth (including basal organic lake sediment, where
present) was measured on a grid and interpolated to calculate mean depth. Our study
addressed three questions: (1) How spatially variable is peat depth? (2) To what degree can
mean peat depth be predicted from other field measurements (water chemistry, water table
depth, vegetation cover, slope) and/or remotely sensed spatial data? (3) How much C is
stored in NHLD peatlands? Site mean peat depth ranged from 0.1 to 5.1 m. Most of the
peatlands had been formed by the in-filling of small lake basins (terrestrialization), and
depths up to 15 m were observed. Mean peat depth for small peat basins could be best
predicted from basin edge slope at the peatland/upland interface, either measured in the
field or calculated from digital elevation (DEM) data (Adj. R2 = 0.70). Upscaling using the
DEM-based regression gave a regional mean peat depth of 2.1 plus or minus 0.2 m (including
approximately 0.1 to 0.4 m of organic lake sediment) and 144 plus or minus 21 Tg-C in total.
As DEM data are widely available, this technique has the potential to improve C storage
estimates in regions with peatlands formed primarily by terrestrialization. Number of sites:
21 Sampling Frequency: once for each site