Modelling the Response of Loblolly Pine to Juvenile Fertilization

This paper presents a dominant height and basal area response function for juvenile (ages 2-8) loblolly pine stands that have been fertilized with a combination dose of 200 lbs/ac of nitrogen and 50 lbs/ac of phosphorus. The data used to construct the response functions originated from the Region-wide 2 Study of the North Carolina State University Forest Nutrition Cooperative. The data set included field plots from three physiographic regions and states spanning the southeastern United States from Alabama to Delaware. The dominant height response model is a function of the time elapsed since fertilization (years since treatment) and soil drainage of the Coastal Plain soils. The basal area response model is a function of years since treatment. The response functions must be used sequentially since basal area response is understood as an incremental gain in basal area over the increase in basal area already explained by the response in dominant height. The response in dominant height typically ranges from 1-2 feet, six to eight years after treatment on all soils except the well drained Coastal Plain soils. The total increase in basal area ranges from 10-12 ft/ac, six to eight years after treatment on all soils except the well drained Coastal Plain soils. The parameters of both models were estimated using the Mixed Models with Repeated Measures methodology.