Ground vegetation exceeds tree seedlings in early biomass production and carbon stock on an ash-fertilized cut-away peatland

Afforestation is one of the most popular after-use options of cut-away peatlands in Scandinavia since it has both economic and aesthetic values and therefore the interest concerning the carbon stock often focuses on tree stands. Consequently, ground vegetation is readily disregarded in the present calculations of the climatic impact of afforestation. However, at the early stages of afforestation vigorous ground vegetation may have a major role in carbon sequestration. The biomass and C stock of ground vegetation and young tree seedlings were examined on an ash-fertilized and afforested cut-away peatland. Six treatments of different mixtures and quantities of wood-ash, peat-ash, biotite or Forest PK-fertilizer were replicated in three plots. Betula pubescens Ehrh. seeds were sown on randomized halves of split plots while the other halves were left unsown. The plant biomass was harvested four growing seasons after the treatments. The live above-ground biomass of ground vegetation on a cut-away peatland was up to two times that of tree seedlings. Furthermore, the below-ground biomass of ground vegetation and tree seedlings was equal to the above-ground biomass, or even greater. In particular, the biomass of mosses multiplied on ash-based fertilized areas compared to the Forest PK-fertilized areas. Our study proved that at the early stages of afforestation ground vegetation was even more important in biomass production and C stock than tree seedlings. Consequently, our results suggest that ground vegetation biomass should also be considered when the climatic impact of afforestation of cut-away peatlands is being calculated.