Impact of Ash-Fertilization and Soil Preparation on Soil Respiration and Vegetation Colonization on Cutaway Peatlands

Abstract

As a result of several decades of peat extraction, the area of cutaway peatlands in Finland totals ca. 50,000 ha. Furthermore, some 2000 - 3000 ha of peatlands are abandoned annually from active peat extraction. Forestry is considered to be their main after-use option. However, since cutaway peat is generally rich in nitrogen, but poor in phosphorus and potassium, soil amelioration measures are needed for successful vegetation and afforestation. Soil preparations bringing mineral soil into peat surface or recycling of ash containing P and K are alternative ways for soil amelioration. We studied the initial effects of soil preparation and ash fertilization on soil CO2-effluxes and colonisation of cutaway peat by vegetation. Oppositely to the previous studies, this study shows that carbon released from the residual peat may be so high that the ash-fertilized cutaway peatlands still act as sources of carbon even after afforestation. However, even though the CO2-effluxes following ash fertilization or soil preparation may occasionally exceed the carbon sequestration into growing tree stands, afforestation mostly compensates the CO2-effluxes if also we take into consideration the below-ground biomass. In conclusion, our study shows that although ash fertilization enhances the CO2-effluxes into the atmosphere, it has beneficial effects on the environment by enabling rapid colonisation of vegetation on these sites which would remain vegetationless for decades without soil amelioration.