Loblolly pine needle decomposition and nutrient dynamics as affected by irrigation, fertilization, and substrate quality

摘要

This study examined the effects of initial litter quality and irrigation and fertilization treatments on litter decomposition rates and nutrient dynamics (N, Ca, K, Mg, and P) of loblolly (Pinus taeda L.) pine needles in the North Carolina Sand Hills over 3 years. Litter quality was based on the initial ON ratios, with the high-quality litter having a significantly (P < 0.001) lower CIN ratio (143 +/- 2.5) compared with the low quality litter (172 +/- 1.3). Initial litter quality and the irrigation treatment did not significantly affect decomposition rates but the fertilization treatment effects were significant. Low quality needles on fertilized plots had higher decomposition rates (k = 0.36 +/- 0.01 year(-1) for the fertilized and irrigated + fertilized plots) than on unfertilized plots (k = 0.26 +/- 0.01 and 0.28 +/- 0.01 year(-1) for the control and irrigated plots, respectively). The decomposing litter was a net sink for P and N and a net source of Mg, Ca, and especially K. Whereas initial substrate quality did not affect decomposition rates, it did affect the rate of release. Compared to the low quality litter, the high quality litter released K at a higher rate, released Mg at a lower rate, and accumulated N at a higher rate. Fertilization decreased the rate of release of Mg and K in high-quality litter and Mg and Ca in low quality litter. In addition, fertilization increased the rate of accumulation of P in both.