ABOVE AND BELOW-STUMP BIOMASS AND NUTRIENT CONTENT OF A MATURE LOBLOLLY-PINE PLANTATION

Above- and below-stump biomass and nutrient content were estimated for a mature loblolly pine (Pinus taeda L.) plantation on an eroded site in the upper Piedmont of South Carolina. Pine above-stump biomass was 144.9 t . ha(-1); below-stump biomass was 36.0 t . ha(-1), 20% of total pine biomass. Total pine biomass was partitioned as 17% crown, 63% stem, and 20% roots. About 55% of below-stump biomass was in taproots and 45% in lateral roots. Dominant and codominant trees had a greater proportion of below-stump biomass in lateral roots, indicating that larger trees absorb a disproportionate quantity of the site's moisture and nutrients. Lateral roots contained 66 to 75% of below-stump nutrients. Fine roots (<0.6 cm diameter) accounted for 11% of below-stump biomass, but contained 24 to 30% of below-stump nutrients. Nutrient content (kg . ha(-1)) of above-stump biomass ranked as follows: N 164.7, Ca 154.2, K 78.0, and P 14.0. Nitrogen was also the most abundant nutrient in below-stump biomass (60.2 kg . ha(-1)), followed by Ca (48.9 kg . ha(-1)), K (41.2 kg . ha(-1)), Mg (11.1 kg . ha(-1)), and P (7.5 kg . ha(-1)). Below-stump biomass contained 27, 35, 35, and 24% of total pine N, P, K, and Ca, respectively. Fine roots and foliage, only 4% of total stand biomass, had about one-fourth of the stand's N and P.