COS 1-1 - Variability in permafrost depth and potential biogeochemical indicators in Alaskan peatlands

Monday, August 8, 2016: 1:30 PM
304, Ft Lauderdale Convention Center
John E Anderson, Army, Geospatial Research Lab, Woodford, VA, Robyn A. Barbato, Army, US Army Cold Regions Research and Engineering Lab, Hanover, NH, Thomas Douglas, Army, Cold Regions Research Laboratory, Fairbanks, AK and Stephen Newman, Army, Cold Regions Research and Engineering Laboratory, Hanover, NH

Boreal wetlands in interior Alaska include bogs, fens, muskegs and associated aquatic regions that are underlain by sporadic bodies of discontinuous permafrost. Permafrost, cryotic soil at or below 0°C for multiple years, is situated in the earth’s higher latitudes where it acts as a confining layer in the shallow subsurface on which wetlands are perched.  Much of the permafrost in interior Alaska is blanketed by surface vegetation, organic mat, and soil components that are thermally stable. When this protection is altered, the response of permafrost is rapid. As mean annual temperatures in interior Alaska are projected to increase 5°C within the next 80 years, this warming is expected to initiate widespread permafrost degradation altering biogeochemical conditions affecting soils, vegetation, and microbial communities. It is these conditions that, once changed, act as ‘accelerants’ in the degradation of permafrost.  At three sites in the Alaska interior near Fairbanks we are measuring plant species composition and diversity, REDOX (Eh), pH, permafrost depth, soil microflora activity, terrain elevation, and temperature (by thermistor).  Our goal is to use these data to model these processes to better understand and forecast the conditions that foster acceleration dynamics. 

An assessment of 30 plant species along transects within 2 m2 quadrats indicates species diversity and composition vary greatly among the sites with the greatest diversity corresponding to sites having shallower permafrost depths (< 50 cm). The sites with deeper permafrost (> 100 cm) and greater water content exhibited the lowest plant diversity.  We also found through correspondence analysis that three plant species are highly correlated with deeper permafrost while the remainder either correlate with elevation or soil pH.  Furthermore, REDOX (Eh) changes occurring from permafrost degradation may impact plant uptake of nutrients and the regulation of soil processes, though there appears to be little association between plant diversity and redoxymorphic condition.  In sites with shallower permafrost depth , soil conditions were significantly more reducing (P<0.0001) and total C and N utilization by soil microflora were elevated.  In these reducing systems, β-glucosidase targeting sugars and leucine aminopeptidase targeting proteins were active at both 5 and 25°C, suggesting a sustained activity under low temperature regimes.  Finally, soil temperatures along bog-to-forest transitions showed fluctuations for deep versus shallow measurements during the growing season.  These measurements indicate warmer trending soil temperatures at depths below 1 m as the transition moves to forested conditions, while bog temperatures remain colder and more stable.