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Moisture controls on carbon dioxide dynamics of peat‐ Sphagnum monoliths
Author(s) -
Strack M.,
Price J. S.
Publication year - 2009
Publication title -
ecohydrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.982
H-Index - 54
eISSN - 1936-0592
pISSN - 1936-0584
DOI - 10.1002/eco.36
Subject(s) - sphagnum , peat , water content , environmental science , moss , water table , mire , moisture , carbon dioxide , bog , hydrology (agriculture) , soil science , atmospheric sciences , botany , geology , ecology , chemistry , groundwater , biology , geotechnical engineering , organic chemistry
Sphagnum moss is the major peat‐forming vegetation component in boreal peatlands. The relationship between Sphagnum productivity and moss moisture content has been documented; however, the link between moss moisture content and conditions in the underlying peat column is less clear. We conducted a pilot study in which we monitored volumetric moisture content with depth and gravimetric water content of Sphagnum capitula and CO 2 exchange for two peat monoliths with intact moss layer dominated by Sphagnum fuscum and S. magellanicum . Measurements were made under drying conditions and rewetting from below and following simulated precipitation events. Capitulum moisture content was related to water table position but varied between species. Both capitulum moisture content and water table position could be used to explain net CO 2 exchange and respiration during drying and rewetting from below, although hysteresis was apparent where respiration was lower on rewetting than drying for the same water table position. Precipitation complicated these relationships because small events (<5 mm) rewetted the upper few centimeters of moss resulting in a change in capitulum moisture content equivalent to a rise in water table position of ∼20 cm. This change in capitulum moisture content resulted in substantial shifts in both photosynthesis and respiration rates without affecting water table position or subsurface volumetric water contents as shallow as 5 cm below the surface. While these small events will be difficult to measure in the field, this study suggests they are essential to effectively track or model Sphagnum productivity because they may contribute significantly to seasonal carbon balance. Copyright © 2009 John Wiley & Sons, Ltd.