Quantifying the coarse-root biomass of intensively managed loblolly pine plantations

Most of the carbon accumulation during a forest rotation is in plant biomass and the forest floor. Most of the belowground biomass in older loblolly pine (Pinus taeda L.) forests is in coarse roots, and coarse roots persist longer after harvest than aboveground biomass and fine roots. The main objective was to assess the carbon accumulation in coarse roots of a loblolly pine plantation that was subjected to different levels of management intensity. Total belowground biomass ranged from 56.4 to 62.4 Mt.ha(-1) and was not affected by treatment. Vegetation control and disking increased pine taproot biomass,and decreased hardwood taproot biomass. Pines between tree coarse roots were unaffected by treatment, but hardwoods between tree coarse roots were significantly reduced by vegetation control. Necromass was substantially lower than between-tree biomass, indicating that decomposition of coarse-root biomass from the previous stand was rapid for between-tree coarse roots. Total aboveground biomass was increased by vegetation control, with the lowest production on the least intensively managed plots (180.2 Mt.ha(-1)) and the highest production on the most intensively managed plots (247.3 Mt.ha(-1)). Coarse-root biomass ranged from 19% to 24% of total biomass. Silvicultural practices increasing aboveground pine productivity did not increase total coarse-root biomass carbon because of the difference in root/shoot allocation between pine and hardwood species.