Investigating the controls on soil organic matter decomposition in tussock tundra soil and permafrost after fire

• Published in: Soil Biology and Biochemistry
• Main Authors: De Baets, S., Van de Weg, M. J., Lewis, R., Steinberg, N., Meersmans, Jeroen, Quine, T. A., Shaver, G. R., Hartley, I. P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Ltd 2016
• Subjects: Alaskan arctic soils; Anaktuvuk fire; C sequestration; Soil respiration; Tussock tundra; Atmospheric temperature; Biogeochemistry; Biological materials; Carbon; Carbon dioxide; Decay (organic); Fires; Landforms; Low temperature production; Minerals; Nitrogen; Organic compounds; Permafrost; Thawing; Upper atmosphere; Arctic soil; Labile organic matter; Nitrogen availability; North Slope of Alaska; Nutrient availability; Soils; Alaska; Anaktuvuk River; North Slope; United States; Life sciences; Environmental sciences & ecology; Sciences du vivant; Sciences de l’environnement & écologie; Arctic; north slope; permafrost; Tundra
• Online Access: https://orbi.uliege.be/handle/2268/264877; https://doi.org/10.1016/j.soilbio.2016.04.020

peer reviewed Rapid warming in Arctic ecosystems is resulting in increased frequency of disturbances such as fires, changes in the distribution and productivity of different plant communities, increasing thaw depths in permafrost soils and greater nutrient availability, especially nitrogen. Individually and collectively, these factors have the potential to strongly affect soil C decomposition rates, with implications for the globally significant stores of carbon in this region. However, considerable uncertainty remains regarding how C decomposition rates are controlled in Arctic soils. In this study we investigated how temperature, nitrogen availability and labile C addition affected rates of CO2 production in short (10-day for labile C) and long-term (1.5 year for temperature and N) incubations of samples collected from burned and unburned sites in the Anaktuvuk river burn on the North Slope of Alaska from different depths (organic horizon, mineral horizon and upper permafrost). The fire in this region resulted in the loss of several cms of the organic horizon and also increased active layer depth allowing the impacts of four years of thaw on deeper soil layers to be investigated. Respiration rates did not decline substantially during the long-term incubation, although decomposition rates per unit organic matter were greater in the organic horizon. In the mineral and upper permafrost soil horizons, CO2 production was more temperature sensitive, while N addition inhibited respiration in the mineral and upper permafrost layers, especially at low temperatures. In the short-term incubations, labile C additions promoted the decomposition of soil organic matter in the mineral and upper permafrost samples, but not in the organic samples, with this effect being lost following N addition in the deeper layers. These results highlight that (i) there are substantial amounts of labile organic matter in these soils (ii), the organic matter stored in mineral and upper permafrost in the tussock tundra is less readily ...