Carbon Gain and Allocation in Five Shade Intolerant Pinus Species

Pinus virginiana (Virginia pine), Pinus echinata (shortleaf pine), Pinus taeda (loblolly pine), Pinus elliottii (slash pine), and Pinus palustris (longleaf pine) are five of the most dominant shade-intolerant pine species in the southeast region. These five species have overlapping geographic ranges, tolerate poor soil conditions and low water availability conditions, and have relatively high volume growth rate. Among the five species, P. virginiana and P. echinata have the shortest needles of around 5-7 cm. P. taeda and P. elliottii have the intermediate needle length of around 15-22 cm, while P. palustris has the longest needles of around 30 cm. To compare the among species differences in biomass growth rate based on their physiology, morphology, and hydraulics related leaf traits, shoot and crown structure, and biomass allocation, we collected the data from an experimental site in Duke Forest and compared the performance of these five species when trees of the same age were grown under the same climate and soil conditions. Our study revealed distinct differences in allometric relationships and biomass allocation patterns among the five species. Analysis of leaf functional traits and crown structure showed variation in the ability to support leaf area at a given leaf mass, branch mass, and sapwood area across species. Finally, the differences in total biomass and wood production among species reflected the combined effect of leaf area index and biomass allocation pattern. We found that, when growing in one environment, species with intermediate needle length (P. taeda and P. elliottii) were more efficient in biomass production and volume growth while balancing the investment in intercepting light and maintaining hydraulic system. The results of this study indicated that growth-related functional traits, combined with biomass allocation patterns that favor stem and aboveground production, make P. taeda and P. elliottii among the fastest growing conifers with high timber values, regionally and globally.