Premium
Effects of simulated spring thaw of permafrost from mineral cryosol on CO 2 emissions and atmospheric CH 4 uptake
Author(s) -
Stackhouse Brandon T.,
Vishnivetskaya Tatiana A.,
Layton Alice,
Chauhan Archana,
Pfiffner Susan,
Mykytczuk Nadia C.,
Sanders Rebecca,
Whyte Lyle G.,
Hedin Lars,
Saad Nabil,
Myneni Satish,
Onstott Tullis C.
Publication year - 2015
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2015jg003004
Subject(s) - tundra , environmental chemistry , permafrost , biogeochemical cycle , arctic , chemistry , dissolved organic carbon , methanogenesis , heterotroph , carbon dioxide , autotroph , methane , environmental science , ecology , geology , paleontology , organic chemistry , bacteria , biology
Previous studies investigating organic‐rich tundra have reported that increasing biodegradation of Arctic tundra soil organic carbon (SOC) under warming climate regimes will cause increasing CO 2 and CH 4 emissions. Organic‐poor, mineral cryosols, which comprise 87% of Arctic tundra, are not as well characterized. This study examined biogeochemical processes of 1 m long intact mineral cryosol cores (1–6% SOC) collected in the Canadian high Arctic. Vertical profiles of gaseous and aqueous chemistry and microbial composition were related to surface CO 2 and CH 4 fluxes during a simulated spring/summer thaw under light versus dark and in situ versus water saturated treatments. CO 2 fluxes attained 0.8 ± 0.4 mmol CO 2 m −2 h −1 for in situ treatments, of which 85 ± 11% was produced by aerobic SOC oxidation, consistent with field observations and metagenomic analyses indicating aerobic heterotrophs were the dominant phylotypes. The Q 10 values of CO 2 emissions ranged from 2 to 4 over the course of thawing. CH 4 degassing occurred during initial thaw; however, all cores were CH 4 sinks at atmospheric concentration CH 4 . Atmospheric CH 4 uptake rates ranged from −126 ± 77 to −207 ± 7 nmol CH 4 m −2 h −1 with CH 4 consumed between 0 and 35 cm depth. Metagenomic and gas chemistry analyses revealed that high‐affinity Type II methanotrophic sequence abundance and activity were highest between 0 and 35 cm depth. Microbial sulfate reduction dominated the anaerobic processes, outcompeting methanogenesis for H 2 and acetate. Fluxes, microbial community composition, and biogeochemical rates indicate that mineral cryosols of Axel Heiberg Island act as net CO 2 sources and atmospheric CH 4 sinks during summertime thaw under both in situ and water saturated states.