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Effects of extreme experimental drought and rewetting on CO 2 and CH 4 exchange in mesocosms of 14 European peatlands with different nitrogen and sulfur deposition
Author(s) -
EstopAragonés Cristian,
Zając Katarzyna,
Blodau Christian
Publication year - 2016
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.13228
Subject(s) - ombrotrophic , peat , bog , sphagnum , mesocosm , deposition (geology) , respiration , nitrogen , environmental science , environmental chemistry , humus , ecosystem respiration , methanogenesis , chemistry , primary production , ecology , ecosystem , soil water , soil science , botany , methane , biology , paleontology , organic chemistry , sediment
The quantitative impact of intense drought and rewetting on gas exchange in ombrotrophic bogs is still uncertain. In particular, we lack studies investigating multitudes of sites with different soil properties and nitrogen (N) and sulfur (S) deposition under consistent environmental conditions. We explored the timing and magnitude of change in CO 2 (Respiration, Gross Primary Production – GPP , and Net Exchange – NE ) and CH 4 fluxes during an initial wet, a prolonged dry (~100 days), and a subsequent wet period (~230 days) at 12 °C in 14 Sphagnum peat mesocosms collected in hollows from bogs in the UK , Ireland, Poland, and Slovakia. The relationship of N and S deposition with GPP , respiration, and CH 4 exchange was investigated. Nitrogen deposition increased CO 2 fluxes and GPP more than respiration, at least up to about 15 kg N ha −1 yr −1 . All mesocosms became CO 2 sources during drying and most of them when the entire annual period was considered. Response of GPP to drying was faster than that of respiration and contributed more to the change in NE ; the effect was persistent and few sites recovered “predry” GPP by the end of the wet phase. Respiration was higher during the dry phase, but did not keep increasing as WT kept falling and peaked within the initial 33 days of drying; the change was larger when differences in humification with depth were small. CH 4 fluxes strongly peaked during early drought and water table decline. After rewetting, methanogenesis recovered faster in dense peats, but CH 4 fluxes remained low for several months, especially in peats with higher inorganic reduced sulfur content, where sulfate was generated and methanogenesis remained suppressed. Based on a range of European sites, the results support the idea that N and S deposition and intense drought can substantially affect greenhouse gas exchange on the annual scale.