3. Results
3.1. Species growth
Table 1 summarizes the most important growth indices for
the selected species after six years of growth. As discussed by
[13] the species with the best adaptation and growing pattern for southern region of Costa Rica on acid soils (Eco-region 1
and 2) were the two introduced species Gmelina arborea and
Pinus caribaea followed by the two native Vochysias. In volcanic
soils (Eco-region 3) and alluvial soils (Eco-region 4) the Hieronyma
alchorneoides and Terminalia amazonia resulted in
comparable adaptability and productivity indices as the two
Vochysia species, a clear indication that these two native
species prefer more fertile soils (Andisols and alluvial Inceptisols)
with a shorter dry season.
3.2. Aboveground biomass
Fig. 1 shows the distribution of aboveground biomass by tree
compartment and the variations according to tree dimensions
(DBH, tree height and total dry weight) for each species (n¼ 4).
A common tendency for all the species is the increase in stem
biomass as tree dimensions increase. This pattern is particularly
evident in Terminalia amazonia whose trees of smaller
dimensions the stem represents only 40% of the total aboveground
biomass, while for trees of larger dimensions, the stem
represents up to 80% of the total biomass. An inverse
tendency in this same species is shown for foliage, branch and
bark biomass, their percentages decrease as tree dimensions
increase. Looking at the differences between species, the
largest portion of aboveground biomass is concentrated in the
stems of Hieronyma alchorneoides and Gmelina arborea. These
two species distribute between 70% and 80% of their aboveground
biomass in the stems regardless of tree dimensions.
The percentage of bark in Pinus caribaea is also notable, representing
approximately 14% of the total biomass, while for
the rest of the species it does not surpass 7%.
Table 2 shows the means multiple comparisons for
aboveground biomass content according to tree compartments
at 6 years of age. The species with the highest stem
biomass is G. arborea which is an expected result due to the
larger dimensions of sampled trees. P. caribaea by far has the
highest bark biomass followed by G. arborea, while T. amazonia
is the species with the least bark biomass. V. ferruginea has the
highest branch biomass followed by the group of V. guatemalensis,
P. caribae and G. arborea. Foliage biomass is the highest
for G. arborea followed by P. caribaea and V. ferrugenia.
Table 3 includes a set of allometric equations used to
estimated biomass by tree compartment and whole tree for
each study species or group of species. These equations were
developed using the 24 sampled trees for the biomass analysis.
Fig. 1 provides extra information that provides the range
of DBH values for which these equations should be applied.