ALKÄRR - KÄLLA ELLER SÄNKA FÖR VÄXTHUSGASERNA METAN OCH LUSTGAS? Empirisk studie av växthusgasutbyte i kustnära alkärr på den svenska Västkusten.

Abstract

Due to global climate change and the rising levels of greenhouse gases (GHG) in the atmosphere, the interest for seeking solutions for mitigation has increased. While much attention has been directed towards technical solutions such as carbon capture and storage (CCS), biogenic carbon sinks has also garnered significant attention. Previous studies have shown that coastal ecosystems such as seagrass meadows and mangroves have a much greater capacity for storing carbon (C) compared to terrestrial ecosystems. That raises the question if other coastal ecosystems, such as coastal wetland forests, that previously haven’t been considered as blue carbon habitats also contribute to coastal carbon sink capacity. However, several studies have shown that coastal wetlands produce and emit large quantities of methane (CH4) and nitrous oxide (N2O) which may counteract the role as a sink for carbon dioxide (CO2). It is therefore important to consider this offset of GHG emissions when evaluating their role as blue carbon sinks. This study aims to quantify the CH4 and N2O fluxes within riparian alder forests on the west coast of Sweden. To be able to sample the gas fluxes static chambers were set out in four different alder forests adjacent to the Gullmars fjord. The concentrations were measured using a Picarro® G2508 Gas Concentration Analyzer and then recalculated into a rate, i.e. change in concentration per square meter and hour. Flux rates were then compared to, amongst other things, dissolved oxygen (DO) and water saturation as well as amount of organic matter in the sediments. There was trend that DO was negatively correlated to the CH4 -rate, telling us that with less O2 present the more CH4 will be produced. The opposite could be found for water saturation and organic matter in sediment, more water and organic matter resulted in lower rates for CH4 production. However, none of the models above showed any statistical significance to the results, most probably due to small sample sizes. However, they do give an indication of possible correlations that have been discussed in earlier studies.