ÄR KUSTNÄRA ALKÄRR I BOHUSLÄN ETT ”BLUE CARBON” HABITAT?

Abstract

In coastal wetlands carbon/organic matter can be stored for long periods of time thanks to, among other things, the presence of water which slows down the decomposition. Because of this, restauration and management of such habitats have the potential to decrease the emission of greenhouse gasses and help mitigate climate. Internationally these environments are called “blue carbon” ecosystems. In Sweden, alder (Alnus glutinosa and Alnus incanata) covered wetlands along the coast is a nature type that potentially could function as a “blue carbon” habitat. Sediment samples were taken in four alder wetlands to study the amount of organic matter in the soil and if it varied between sampling sites. At each site basal area, tree height, ground coverage of plants and salinity were measured to examine if there is any correlation between these parameters and the amount of organic matter in the soil. The sediment was dried in the lab and weighed to determine the density and water content in each sample. Loss on ignition was used to find the amount of organic material in the samples. The results showed that the organic material varied between 11,51 ± 0,41 kg/m2 and 23,2 ± 6,17 kg/m2, a one-way ANOVA showed wasn’t a significant difference (p = 0,08). The total amount of organic matter in the wetlands varied between 30,16 and 125,53 tonnes. Correlation was found between the amount of organic material and the density of the sediment in the form of a negative exponential relationship (R² = 0,8342, p <0,01), which have been noted in studies in both seagrass meadows and mangrove forests. No correlation was found between organic matter and basal area, tree hight, ground coverage of plants or salinity. The amount of organic matter is in level with global values for stored organic carbon in seagrass meadows and salt marshes, which suggests that coastal alder wetlands may have similar capacity to store carbon/organic material as the established “blue carbon” habitats.