The growth rate of vegetation in wetlands is often high, which means large amounts of carbon dioxide (CO2) can be captured from the atmosphere and stored in wetland vegetation. Carbon (C) is stored both in living vegetation, as well as in litter, organic soils and sediments. Because of largely anaerobic soil conditions, the C incorporated into the soil decomposes very slowly. In effect, wetlands can act as a long-term C-sinks. Creating or restoring wetlands can therefore be one way of mitigating climate change.
Over the course of 18 years, since the construction of the experimental wetland facility in 2002, extensive peat-like root mats have formed in the wetlands that were initially planted with emergent vegetation. In order to quantify the C storage in these root mats, we have collected samples from three of our experimental wetlands and analysed their C-contents.
Prior to sampling, the wetlands were drained, and all reeds were cut and removed, leaving only the root mats in the wetland basins. Then we collected nine samples from three wetlands initially planted with emergent vegetation. The samples were sawn-out rectangular cores taken evenly distributed within each wetland.
a) Overview of one wetland where nine root mat samples were collected. b) Cross-section of a wetland showing the root mat and three rectangular sample cores.
After collection, samples were frozen and dried. Subsamples were then ground up and analysed for carbon and nitrogen contents using an NC Analyzer. Additional data we collected includes hight and weight of samples.
Pictures taken during the carbon storage study. 1) One of the mature wetlands before we commenced this study. 2) The same wetland, after vegetation and part of the root mat was removed. 3) One sample core. 4) How the wetlands looked when the entire root mat had been removed. We tried to restore the wetlands to their original design, and thus keeping the 45-degree angle on the sides.
The results from this study are presented in Katarzyna Nowak’s master’s thesis Carbon storage in free water surface constructed wetlands in southern Sweden, which can be downloaded in full text here.
Participants
Antonia Liess, Senior Lecturer
Katarzyna Nowak, MSc student
Matyas Baan, Research assistant; MSc student
Josefin Nilsson, PhD student
Stefan Weisner, Senior Professor
Per Magnus Ehde, Research Engineer