LEUCAENA AS A SHORT-ROTATION WOODY BIOENERGY CROP

The tropical leguminous shrub/tree, leucaena (Leucaena spp. mainly leu cocephala), is adapted to well-drained soils; long, warm growing seaso ns; and mild winters. These conditions are common in Florida and the h umid lower South. In much of this area the topgrowth is killed by fros t during winter, with plants regenerating from underground parts each spring. Leucaena can grow for many years in warmer sites, forming a sm all tree. Selected accessions from a duplicated 373-accession leucaena nursery that were harvested annually for four seasons in the 1980s ha d an average annual woody stem dry matter production of 31.4 Mg ha(-1) . Beginning in 1990 through the 1993 season, a sucession of warm winte rs allowed continued leucaena growth for four growing seasons. Average oven-dry stem wood yield from 10 accessions selected for good stand a nd high yields, adjusted for environmental enrichment over the four gr owing seasons, was 76.9 Mg ha(-1) total and an average annual yield of 19.7 Mg ha(-1). Average tree height over the 10 four-year-old leucaen a accessions studied was 8.2 m, with 21 stems per 6 m(2) plot, and ave rage stem diameter breast height (dbh) of 7.3 cm at harvest in January 1994. Ninety-five of the accessions in the nursery still persisted af ter 15 years. Plant vigor and stems per plot, plant form and seed prod uction are reported for 25 of the best surviving leucaena accessions. Leucaena can serve as a short rotation woody biomass crop with annual, biennial and/or multiple-year harvests depending upon need, use, and weather.