Reactive dissolved organic carbon dynamics in a changing environment : Experimental evidence from soil and water
Author
Summary, in English
In a boreal forest region that has seasonal soil frost, the DOC bio-reactivity decreased with experimental reductions in the extent and duration of soil frost, while photo-reactivity remained constant. However, DOC from experimentally thawed permafrost peat in the subarctic north showed higher bio- and photo-degradation potentials than the DOC from active peat layers above the permafrost. The nature of the soil and intrinsic DOC properties explained these patterns in soil DOC reactivity. In the surface water network, bio-degradation was the dominant DOC degradation mechanism in brow-water lakes, while photo-degradation played a relatively larger role in clearer waters. The surface water photo-reactivity per unit of light absorption was high at both acidic and at alkaline conditions, while lower at intermediate pH, probably due to effects of the protonation state of DOC on photo-reactivity. Therefore, pH change along the aquatic network caused extrinsic control on the photo-reactivity at the landscape scale.
In conclusion the results show that climate warming decreases the export of bio-reactive DOC in a boreal forest, but it likely increases the export of bio- and photo-reactive DOC in a permafrost peatland. In a wetter climate with shorter residence times, clear waters may experience browning and relative shift from photo-degradation to bio-degradation, while already brown lakes will remain brown and dominated by bio-degradation. Furthermore, the loss of photo reactive DOC during transport in aquatic network may be counter balanced by the changes in extrinsic variables such as pH.
Department/s
Publishing year
2016-09
Language
English
Full text
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Document type
Dissertation
Publisher
Lund University, Faculty of Science, Department of Physical Geography and Ecosystem Science
Topic
- Physical Geography
Keywords
- Dissolved organic carbon
- DOC
- Photodegradation
- Biodegradation
- DOC reactivity
Status
Published
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-85793-60-0
- ISBN: 978-91-85793-59-4
Defence date
14 October 2016
Defence time
10:00
Defence place
Geocentre I, lecture hall “Världen”, Sölvegatan 10, Lund
Opponent
- Nigel Roulet (Professor)