Land-use scenarios for Finnish cut-over peatlands - based on the mineral subsoil characteristics

Abstract

In Finland, peat harvesting sites are exploited down almost to the mineral soil and the properties of mineral subsoil have considerable influence on the suitability for the various afteruse forms. Chemical and physical features of the mineral subsoil must be studied when after-use is planned, to ensure no harmful effects follow. Research on mineral subsoils was carried out on Finnish peat production sites in 1997 – 1998 and 9800 hectares of peat production areas slowly getting exhausted were studied. The cutover area clearly suitable for forestation covered 57 % of the study area. The area well suitable for agriculture or energy crop growing covered 26 – 42 % of the study – depending if boulder-poor tills were included or excluded. Even larger areas might be possible for agriculture if for example remaining peat layer was used for compensating physical features of the mineral subsoil. Approximately 11 % was recommended for mire regeneration because of sensitive bottom soils, but much larger areas were possible for mire regeneration. In 9 % of all cases fine miner al subsoils were on pool-forming locations and would this way offer sites best suitable for mire regeneration or even bird sanctuaries. Both EC and pH of the mineral subsoils were related to the presence of sulphur. The concentrations of Ca, Mg and K followed the finematerial percentage. Based on this study minimum analysis recommended was for pH, sulphur content and fine material (< 0.06 mm) percentage. Other relevant elements were calcium, magnesium and potassium. Different land-use scenarios were created for areas in after-use, released from peat production and in peat production (2004). These scenarios were based on the mineral subsoil suitability for different after-use forms. In these scenarios the total area annual carbon fixation values varied between 0.096 and 0.152 million t C a -1 , when carbon emissions were not included.