Fine root production and turnover of tree and understorey vegetation in Scots pine, silver birch and Norway spruce stands in SW Sweden

Abstract

Fine roots contribute to net primary production in forests, but knowledge of fine root longevity and turnover is still incomplete and limited to few tree species. In this study, we used minirhizotrons to compare fine root biomass, longevity and turnover of Pinus sylvestris L., Betula pendula Roth and Picea abies (L) Karst. in southern Sweden. Minirhizotron tubes were installed in 2006 and root images were taken in 2007–2010. Soil cores were used to estimate fine root biomass. Soil samples were taken from the humus layer and from 0 to 10cm, 10 to 20cm and 20 to 30cm depth in the mineral soil. Only images from the humus layer and the upper 10cm of mineral soil were included in root analysis.Spruce has a higher aboveground production than pine and birch in southern Sweden and this was reflected in larger fine root biomass as well as higher fine root biomass production. The annual tree fine root biomass production (humus and 0–30cm in mineral soil) was 73, 78 and 284gm−2 in pine, birch and spruce stands, respectively. Thicker fine roots tended to live longer. The majority of the fine roots were thinner than 0.5mm in diameter, with a turnover rate (KM) of 0.4year−1. When comparing all fine roots, i.e. all roots 0–2mm, pine had the highest longevity, 1120days, compared with 900days for spruce and 922days for birch (KM).