Loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) are the two most important commercial timber species in the southeastern United States. Understanding long-term dynamics of the growth, structure and health of their plantation ecosystems, especially in the different management regimes, will help forest landowners select the proper species for a given site. Most previous studies relied on either an observational study or a short-term experimental study without imposing different management regimes. These studies compared the performance of loblolly and slash plantations at a specific age (or development stage), which lead to inconsistent results.
A species comparison study was established in 1995 in the Lower Coastal Plain of southern Georgia and northern Florida, in which loblolly and slash pine plots were paired for combinations of planting density (741, 2224, 3706 trees/ha) and management intensity (operational and intensive) at nine locations. With data over ages 2-21 years, species comparisons were conducted for average DBH, average height, stand density index, stand total volume and total aboveground biomass.
Destructive biomass sampling was conducted in 2015 to assess biomass allocation and the concentrations of carbon and nutrients in stem wood, bark, branch and foliage. The effects of species, management intensity and planting density on stand-level biomass allocation, carbon and nutrient contents in biomass components were assessed.
Results/Conclusions
When compared on a management intensity and initial density basis, loblolly pine consistently had higher average heights than slash pine, but average DBH did not differ between species. Loblolly pine was less susceptible to fusiform rust and had a higher maximum stand density index than slash pine, and thus its mortality rate was lower than slash pine. As a result, loblolly pine outperformed slash pine in terms of stand basal area, total volume and total aboveground biomass. More intensive management increased species differences in average height, stand volume and biomass. The difference in potential productivity in loblolly and slash pine plantations was partially explained by their differences in biomass allocation and nutrient budgets. C and nutrient concentrations will be discussed.