PS 7-58
Pedicting taproot decompostion of longleaf pine across the southeastern U.S
Storage of below-ground carbon (C) is an important component of total forest C. However, below-ground C changes temporally due to forest growth and tree mortality (natural and via harvesting) and these changes are critical for modeling C in forests under varying management regimes. Little effort has been made to date to quantify the rate of decay of tree root systems. Decomposition rates of longleaf pine taproots were quantified under site conditions across the species range to create a model for necromass loss. A total of 29 longleaf pine taproots were excavated from North Carolina, Georgia, Louisiana, and Florida. The ages of the trees when cut ranged from 14 to 260 and the time since they were cut from 7 to 70 years. Stump diameters (approximating there size at the time they were cut) ranged from 17 to 72 cm in the 14 and 260 year old taproots, respectively. Remaining lateral roots to 1 meter and whole taproot where removed, dried, weighed and analyzed for C. Soil measures included C, density, and texture at 5 depths. Thirty-year mean minimum air temperature for each site was determined using the USDA plant hardiness zones.
Results/Conclusions
Total necromass of the harvested roots ranged from 8 to 195 Kg. A stepwise regression model was developed to predict necromass loss across the species range. This model predicts root necromass as a function of years since cut, stump diameter, and minimum air temperature (R2 = 0.83). Varying scenarios of decomposition patterns over time for trees of different sizes and plant hardiness zones will be presented.