Abstract:
In plantation forestry, rapid growth rate is favorable for wood production, but may decrease wood density, which is an important indicator of wood quality for both pulp and solid wood products. I looked for (1) differences in radial patterns of wood
density between planted and naturally grown Costa Rican tree species, and (2) between species characteristic of different successional stages. Trees were sampled
from seven- and eleven-year-old research plantations and the nearby forests at La
Selva Biological Station, Costa Rica and analyzed by x-ray densitometry at Oregon
State University. Four of eight tree species had significantly higher wood densities for naturally grown trees than for the seven-year-old planted trees as shown by x-ray densitometry. Two species had significantly higher wood density for planted trees, and the two remaining species showed no significant differences between planted and naturally grown trees. Height-diameter ratios for eleven-year-old trees were higher for later successional species than for early successional species, and later successional species showed greater increases in wood density than early successional species. As expected, wood density was lowest in early successional species. The index S (ht/(dia*SG)) was expected to correlate with successional status. S provided an accurate prediction of relative successional order, with high values representing late successional species, due to the unexpected height-diameter ratio results. The results show that early-successional tree species do not necessarily have rapid height growth at the expense of diameter growth, nor a related radial increase in wood density. Different species had different patterns of wood density and/or height-to-diameter ratios that defied simple generalizations. More research is necessary to understand the underlying reasons for this the observed variation, rather than reject outright
previously held generalities in the literature. Preferably, such studies will use older trees, larger sample sizes, and better-documented and more diverse growing
conditions in plantations.
