The effect of geothermal soil warming on the production of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), nitric oxide (NO) and nitrous acid (HONO) from forest soil in southern Iceland

• Published in: Icelandic Agricultural Sciences
• Main Authors: Maljanen, Marja, Bhattarai, Hem Raj, Biasi, Christina, Sigurdsson, Bjarni D.
• Other Authors: Auðlinda- og umhverfisdeild (LBHÍ), Faculty of Natural Resources and Environmental Sciences (AUI), Landbúnaðarháskóli Íslands, Agricultural University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Agricultural University of Iceland 2018
• Subjects: Soil warming; Volcanic soil; Greenhouse gasses; Sitkagreni; Gróðurhúsalofttegundir; Jarðvegsrannsóknir; Jarðhiti; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/989; https://doi.org/10.16886/IAS.2018.02

Geothermal areas can be local sources of greenhouse gases, both directly from the geothermal system or because of soil warming effects on biological sources. In this study we repeated field measurements methane (CH4) and nitrous oxide (N2O) fluxes along the soil temperature (Ts) gradient in a Sitka spruce (Picea sitchensis) stand at the ForHot study site in southern Iceland, where geothermal soil warming had started eight years earlier. We complemented these results with in situ measurements of carbon dioxide (CO2) and topsoil sampled in the same plots to study the production rates of those gases at 20 °C in the laboratory, as well as nitric oxide (NO) and nitrous acid (HONO). We showed that the eight year long exposure to elevated Ts had changed the topsoil, including its microbial properties and the production potentials of these gases. However, the production rates of CO2, CH4 and N2O measured in laboratory conditions did not clearly follow the in situ fluxes. We discuss both adaptation of microbes and origin of greenhouse gases (depth patterns and microbial vs. geothermal sources) as possible reasons for these discrepancies. Jarðhitasvæði geta verið uppsprettur ýmissa gróðurhúsalofttegunda, annað hvort beint upp úr jarðhitakerfinu eða vegna áhrifa aukins jarðvegshita á ýmsa lífræna ferla. Í þessari rannsókn endurtókum við mælingar á flæði metans (CH4) og hláturgass (N2O) með auknum jarðvegshita (Ts) í foldu í sitkagreniskógi (Picea sitchensis) á ForHot rannsóknasvæðinu á Suðurlandi, þar sem jarðhitasvæði hafði færst undir átta árum áður. Við bættum einnig við mælingum á losun koldíoxíðs (CO2) í foldu og bárum - niðurstöðurnar saman við losun þessara sömu gastegunda og nituroxíðs (NO) og nitraðrar sýru (HONO) úr jarðvegskjörnum úr sömu reitum sem mældir voru við 20 °C á rannsóknastofu. Niðurstöðurnar sýndu að átta ára jarðvegshlýnun hafði bæði breytt efnasamsetningu og örveruflóru reitanna og þar með getu til að framleiða áðurnefndar lofttegundir. Hinsvegar breyttist framleiðslugeta CO2, CH4 og N2O við 20 ...