Before the arrival of settlers to the United States, natural communities dominated by longleaf pine (Pinus palustris Mill.) occurred throughout most of the southern Atlantic and Gulf coastal plains. These communities once covered an estimated 20-30 million hectares, or two-thirds of the area in the Southeast. Dissimilar to other southern pines, longleaf pine tolerates a wide variety of habits. It is found growing from dry mountain slopes and ridges to coastal poorly drained flatwoods, as well as the excessively drained sandhills found along the coast and fall line. Today, estimates indicate that less than 1.3 million hectares remain. Ecological restoration and reforestation in the longleaf pine forests has increased over recent years, motivated by both ecological and economic benefits derived from long rotation management strategies. Part of this motivation is driven by the idea that longleaf pine may be better suited to increased levels of CO2 or a warming climate. A series of plots established in young, naturally regenerated longleaf pine stands in south Alabama will be used to investigate potential differences in growth due to differences in climatic factors (represented by different time periods) after reducing the differences in initial stand characteristics as much as possible.
Results/Conclusions In 1964, the U.S. Forest Service established the Regional Longleaf Pine Growth Study to study longleaf pine stand dynamics. To detect possible changes in productivity with time, a series of time replication plots (“timereps”) in youngest age class (ages 9 – 15 years) was established on the Escambia Experimental Forest (EEF) in Brewton, Alabama. The study accounts for possible growth change over time by adding a new set of plots in the youngest age class every 10 years. The first series was established in the mid-1960's and plots have been added every 10 years. The controlled nature and close proximity of the timerep plots already isolate concomitant effects induced by stand characteristics and non-temporal climatic variation. Initial efforts to examine these data found an increased growth trend in basal area increment per year. The parameters of growth and mortality models have not remained stable for long projection periods and need to be modified to account for observed temporal variation in growth. Climatic variables, such as precipitation and maximum and minimum temperatures, or climatic indices derived from these variables need to be considered in growth and mortality modeling, since future growth predictions of longleaf pine stands are dependent on this information.
