Quantifying peat carbon mass in Kenai Peninsula peatlands with
ground-penetrating radar (GPR) and probing
Abstract
Peat carbon (C) is one of the largest pools of soil C globally and is
sensitive to environmental and climatic changes. Peatlands in the Kenai
National Wildlife Refuge have been studied for their hydrology,
vegetation composition and succession, peat accumulation, and similar
characteristics, but their mass of stored C remains unknown. We use a
synthesis of soil and wetland surveying techniques to generate estimates
of C mass at two sites selected for suitable topography and hydrology.
Manual probing of peat depth at 208 points across both sites provided
calibration for radar velocity (medians 0.039 m·ns-1 and 0.037 m·ns-1)
of a low-frequency (100 MHz) ground-penetrating radar (GPR), utilized to
identify peat basal horizons. GPR surveys collected data points more
efficiently than probing: >26,000 traces over 4.9 km of lines
in half the time. We calculated total C mass from basin volume estimates
via kriging interpolation surfaces with peat core C content and bulk
density values, yielding estimates of 4,172 and 3,473 metric tons C (tC)
for the two sites. Nearly equal site surface areas of 2.1 hectares
yielded areal densities of 1,948 and 1,628 tC per hectare, respectively.
Peat core analyses of C isotopes, organic matter content, nitrogen
content, and 14C dating illustrate a similar Holocene history, but site
conditions vary despite proximity. Variances in bulk density, vegetation
abundance and diversity, and surface water presence are likely
influenced by local topography, subsurface hydrologic connectivity, and
the establishment history of peat-forming vegetation.