Effects of regeneration on hydrology and water quality of a managed pine forest
Intensive forest management practices such as drainage, harvesting, site preparation, regeneration, and fertilization have been frequently blamed for problems related to excessive nitrogen, phosphorus, and sediment in receiving waters. Two 25 ha experimental watersheds (D1 control; D2 treatment) on a pine plantation in eastern North Carolina have been monitored since 1988 to study the hydrologic and water quality effects of various silvicultural and water management treatments using a paired watershed approach. Data from a two-year calibration period (1988-90) and a four-year regeneration period (2000-03) were used for the analysis. This study period recorded both the highest (2330 mm in 2003) and lowest (850 mm in 2001) rainfall of the 16-years (1988-2003) of record at this site. Nearly seven years after planting, water table elevations returned back to pre-treatment conditions. However, peak flow rates and consequently annual outflows were generally higher on the treatment watershed D2 compared to the control watershed (D1), indicating that the outflows on the treatment watershed may not have completely returned back to base line conditions. Average outflow nutrient (NO3-N, TKN, and Total-P) concentrations for the treatment (D2) watershed for the period from 2000 to 2003 were, however, similar or somewhat lower than their expected values. Although sediment concentration seems to have slightly increased compared to the calibration period, regeneration did not seem to have any effect by the third year after planting, The water quality concentrations were also much lower than the data reported for agricultural lands in the same region. These results will be evaluated and reported soon in the context of prior data after harvesting in 1995 and planting in 1997 to detect the actual effects of regeneration.