Relationship among aboveground biomass, leaf area and soil types in Eucalyptus grandis plantations from NE Entre Ríos, Argentina.

The objective of this work was to determine if there were differences in aboveground biomass and leaf area, and consequently, in wood mass production and yield in Eucalyptus grandis plantations grown on three soil forest types in Concordia (31° 23' S, 58° 02' W). The study was conducted in three 0.207 ha experimental plots of E. grandis -south african provenance, 14 yrs old, originally planted at 3 x 3m, respectively located on Oxic Quartzipsamment (locally arenoso), Fluventic Haplumbrept (locally mestizo) and Vertic Argiacuol (locally arcilloso) soils. The structural parameters measured were density, basal area and volume. Twenty-two trees in the diameter-height range present in the plots were cut for fresh and dry weight measurement of stems >5 cm diameter, branches <5 >1cm diameter, small branches < 1cm diameter, twigs, leaves and fruits. Dimensional analysis procedures were applied. Biomass (total and by compartment) for each plot was calculated using the regression equations obtained and DBH-height measures of all trees in the plot. The Leaf Area Index (LAI) of each plot was obtained multiplying it specific leaf area (SLA) and leaf biomass. To calculate SLA, 15 groups of 20 leaves of each plot were measured with an optical planimeter and dried to constant weight. A unique model for each tree compartment dry weight estimation was used because there were not significant differences among site models. Significant stand structural differences were observed. The mestizo site showed trees with diameters 20-10 % and height 35-29% more length, 31-33% more basal area and 73% higher volume and Mean Annual Increment (MAI) than the arenoso and arcilloso sites, respectively. The LAI was also higher in the mestizo site. In mestizo site stem biomass and MAI were 351 Mg.ha-1 and 25 Mg.ha-1.yr-1, respectively, and the LAI attained 4.5. For the arenoso and arcilloso sites the correspondent stem biomass, MAI and LAI were, respectively, 200-201 Mg.ha-1, 14-13 Mg.ha-1.yr-1 and 3.3-3.0. We conclude that wood mass and volume yield are strongly influenced by the soil type because texture is probably limiting water availability in both textural soil extremes. Differences in MAI indicate that maximum sustained yield differ among sites. E. grandis wood mass yields in NE Entre Ríos are similar to the higher figures reported for sites in the southern hemisphere.

Key words: Eucalyptus grandis, biomass, regression models, LAI, growth, soils.