Nutrient Changes in Decomposing Loblolly Pine Forest Floor

Abstract In two loblolly pine stands ( Pinus taeda L.), 11 and 32 years of age at study inception, nutrients in litterfall and throughfall were measured, and declines in nutrient content were observed as forest floor layers decomposed for up to 8 years. The forest floors up to 8 years of age in the two stands had similar rates of nutrient release. After 8 years of decomposition, 67% of the C, 27% of the N, 63% of the P, 91% of the K, 67% of the Ca, 79% of the Mg were released from the forest floor materials. In the younger stand, release from the forest floor accounted for 34, 59, 47, and 65%, respectively, of the N, P, K, Ca, and Mg assimilated annually into the aboveground biomass. In the older stand, the forest floor release accounted for 86, 104, 73, 72, and 71%, respectively, of the N, P, K, Ca, and Mg, indicating that as the stand matures, the importance of the forest floor increases in the nutrient cycling process. Nitrogen content of the forest floor appeared to increase through the third year of decomposition and then to decrease when needles and branches were assumed to be the only forest floor inputs. However, when fine particles and throughfall were included as forest floor inputs, no increase in forest floor N was observed.