Crown structure and biomass allocation patterns modulate aboveground productivity in young loblolly pine and slash pine

Crown architecture affects tree growth through control of leaf area and its display for effective light capture and photosynthesis. It may be important to quantify crown traits for effective use of intensive silvicultural practices to improve tree growth in forest plantations. We examined growth and crown characteristics in two families of loblolly pine (Pinus taeda L.) with contrasting growth—superior and average, and one slash pine (Pinus elliottii Engelm.) family, growing at three experimental sites in the West Gulf Coastal Plain of Texas and Louisiana, USA. The families were subjected to two contrasting silvicultural treatments—repeated fertilization and control of competing vegetation (high intensity), and control (low intensity). Families differed in height and diameter growth after the second growing period in the field, and high intensity treatment in general increased tree growth, although family ranks and silvicultural effects were dependent on the experimental site. The families differed in crown and needle traits, and biomass partitioning patterns. Aboveground biomass accumulation was related to crown structure among families, but biomass partitioning was independent of the crown traits. Cultural treatment generally had no effect on crown properties or aboveground biomass partitioning. Slash pine produced significantly smaller crowns than loblolly pine at a given tree size, but was capable of maintaining larger needle area and producing more bole-wood biomass for a given crown volume. Tree growth was highly correlated with accumulated foliage area, but bole-wood production per unit leaf area (growth efficiency) was similar for both pine species. The superior loblolly pine family had the largest number of flushes and a different crown shape than two other families that most likely led to better light-capture and greater carbon assimilation, as this family also produced the greatest aboveground biomass.