TOTAL ABOVEGROUND BIOMASS AND NET DRY-MATTER ACCUMULATION BY PLANT-COMPONENT IN YOUNG EUCALYPTUS-GLOBULUS IN RESPONSE TO IRRIGATION

A system of equations describing total aboveground biomass, the propor tion of total aboveground biomass accumulated by different plant compo nents, and instantaneous net dry matter accumulation fraction is devel oped as a function of tree diameter, height, and the growth rates of d iameter and height. This system is utilized in the analysis of a Eucal yptus globulus fertilization/irrigation experiment in central Portugal . The data were from the period prior to competition-induced mortality in the stands, but previous analyses had reported apparent changes in tree growth rates due to intraspecific competition in the experimenta l stands. The irrigation treatments affected the relationship between tree dimensions and total aboveground biomass as well as the accumulat ion of biomass by different aboveground plant components (p less than or equal to 0.05). There were no differences in these relationships du e to fertilization (p = 0.05), in spite of previously reported increas es in biomass production in response to fertilization. Even though irr igation affects dimensional biomass relationships in E. globulus, anal yses demonstrate that previously reported differences in biomass produ ction and accumulation by the various aboveground plant components are , to a much greater extent, due to changes in the growth rates of diam eter and height among the treatments rather than to the changes in str uctural relationships due to the experimental treatments. (C) 1998 Pub lished by Elsevier Science B.V.