Family Differences in Aboveground Biomass Allocation in Loblolly Pine

The proportion of tree growth allocated to stemwood is an important economic component of growth efficiency. Differences in growth efficiency between species, or between families within species, may therefore be related to how growth is proportionally allocated between the stem and other aboveground biomass components. This study examines genetically related differences in aboveground biomass allocation in loblolly pine. I destructively sampled 58 trees from seven families selected to represent differences in growth rate (fast vs. slow) and crown size(large vs. small). The 15-year-old trees were all planted on the same site at the same spacing. Relative allocation to stem, foliage, and branch wood, and the ratio of foliage biomass to total crown biomass, were examined as a function of the logarithm of DBH. Large-crowned trees, compared to small-crowned trees of similar DBH, differed significantly in percent of total aboveground biomass allocated to the stem and to branch wood. Small-crowned families generally allocated proportionally less biomass to branch wood and more to the stem across the range of tree sizes examined. Relative allocation to foliage biomass did not differ, although lower allocation to branch biomass in small-crowned trees resulted in a significantly greater ratio of foliage to total crown biomass. Comparing trees from fastand slow-growing families, only relative allocation to foliage differed significantly, although a strong interaction between DBH and growth characteristic made interpretation of the relationship difficult. These results suggest that families do differ in relative aboveground allocation, but these differences may not be related to family differences in stemwood productivity. 1Associate Professor, Department of Forestry, Mississippi State University, Mississippi State, MS 39762-9681 Citation for proceedings: Outcalt, Kenneth W., ed. 2002. Proceedings of the eleventh biennial southern silvicultural research conference. Gen. Tech. Rep. SRS–48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 622 p.