Long-term geothermal warming reduced stocks of carbon but not nitrogen in a subarctic forest soil.

Autor: Peplau T; Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany., Schroeder J; Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany., Gregorich E; Ottawa Research and Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, Ottawa, ON, Canada., Poeplau C; Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2021 Oct; Vol. 27 (20), pp. 5341-5355. Date of Electronic Publication: 2021 Jul 10.
DOI: 10.1111/gcb.15754
Abstrakt: Global warming is accelerating the decomposition of soil organic matter (SOM). When predicting the net SOM dynamics in response to warming, there are considerable uncertainties owing to experimental limitations. Long-term in situ whole-profile soil warming studies are particularly rare. This study used a long-term, naturally occurring geothermal gradient in Yukon, Canada, to investigate the warming effects on SOM in a forest ecosystem. Soils were sampled along this thermosequence which exhibited warming of up to 7.7℃; samples were collected to a depth of 80 cm and analysed for soil organic carbon (SOC) and nitrogen (N) content, and estimates made of SOC stock and fractions. Potential litter decomposition rates as a function of soil temperature and depth were observed for a 1-year period using buried teabags and temperature loggers. The SOC in the topsoil (0-20 cm) and subsoil (20-80 cm) responded similar to warming. A negative relationship was found between soil temperature and whole-profile SOC stocks, with a total loss of 27% between the warmest and reference plots, and a relative loss of 3%℃ -1 . SOC losses were restricted to the particulate organic matter (POM) and dissolved organic carbon (DOC) fractions with net whole-profile depletions. Losses in POM-C accounted for the largest share of the total SOC losses. In contrast to SOC, N was not lost from the soil as a result of warming, but was redistributed with a relatively large accumulation in the silt and clay fraction (+40%). This suggests an immobilization of N by microbes building up in mineral-associated organic matter. These results confirm that soil warming accelerates SOC turnover throughout the profile and C is lost in both the topsoil and subsoil. Since N stocks remained constant with warming, SOM stoichiometry changed considerably and this in turn could affect C cycling through changes in microbial metabolism.
(© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
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