Forecasting the Decomposability of Organic Matter in Warming Tundra Soils
Infrared spectroscopy predicted the initial decomposition of active layer and permafrost organic matter in Arctic soils.
Calibration models derived from the mid infrared (MIR) spectra of arctic tundra soils reasonably estimated the amount of carbon dioxide released from decomposing soil organic matter during short-term laboratory incubations. Clays, phenolics, aliphatics, silicates, carboxylic acids, and amides were identified as the most influential soil components predicting the initial decomposition of tundra soil organic matter (SOM).
The potential decomposability of soil organic matter is usually determined from soil incubations, which require a substantial investment of time and effort. Application of MIR calibration models to already collected and archived soils could enable widespread assessments of the potential decomposability of Arctic soil organic matter, which are needed to constrain and benchmark model simulations of the responses of these soils to changing environmental conditions.
Vast amounts of SOM are preserved in arctic soils due to the limiting effects of cold and wet environments on decomposer activity. With rapid high-latitude warming due to climate change, the potential decomposability of this soil organic matter needs to be assessed. A team led by Argonne National Laboratory investigated the capability of MIR spectroscopy to quickly predict the amount of organic matter mineralized to carbon dioxide during short-term incubations of arctic soils. Active layer and upper permafrost soils from four tundra sites on the North Slope of Alaska were incubated for 60 days. A partial least square regression (PLSR) model, constructed from the MIR spectra of all incubated soils, reasonably predicted the amount of carbon mineralized during the incubations. Comparing PLSR models for soil subgroups defined by soil carbon or nitrogen contents and tundra type revealed that the best predictions were obtained for soils with <10% organic carbon and <0.6% total nitrogen. Analysis of loadings and beta coefficients from the PLSR models indicated a small number of influential spectral bands, including those indicating clays, phenolics, aliphatics, silicates, carboxylic acids, and amides present in the soils. Study results suggest that MIR spectroscopy could be a useful tool for estimating the initial decomposability of tundra SOM, particularly for mineral soils and the mixed organic-mineral horizons of cryoturbated soils.
Argonne National Laboratory
This study was supported by the Terrestrial Ecosystem Science program (TES) under the Climate and Environmental Science Division of the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science, under Contract No. DE-AC02-06CH11357 to Argonne National Laboratory.
Matamala, R., Jastrow, J.D., Calderón, F.J., Liang, C., Fan, Z., Michaelson, G.J. and Ping, C.L. “Predicting the decomposability of arctic tundra soil organic matter with mid infrared spectroscopy.” Soil Biology and Biochemistry 129, 1–12 (2019). DOI:10.1016/j.soilbio.2018.10.014