EFFECT OF SPACING ON GROWTH AND BIOMASS DISTRIBUTION IN EUCALYPTUS-CAMALDULENSIS, E-PELLITA AND E-UROPHYLLA PLANTATIONS IN SOUTHEASTERN BRAZIL

The growth and biomass accumulation in different plant parts (includin g root systems) of Eucalyptus camaldulensis, E. urophylla and E. pelli ta planted at three spacings (3 X 1.5 m, 3 X 3 m and 4 X 3 m) and thre e ages (15, 31 and 41 months) were evaluated in the savannah region of central Mines Gerais state in southeastern Brazil. A series of equati ons were produced to estimate per-tree biomass from age, spacing, diam eter and height, and per-hectare biomass using age, spacing and a tall y of toe diameters and heights. Average total productivity at age 41 m onths was of the order E. urophylla > E. pellita greater than or equal to E. camaldulensis, As spacing increased, individual stems increased in diameter and total biomass; however, total biomass production per hectare decreased. Eucalyptus urophylla had 64.8 vs. 42.8, E. pellita 41.3 vs. 28.9 and E. camaldulensis 35.1 vs. 26.9 Mg ha(-1) at 3 X 1.5 vs. 4 X 3 m spacings, respectively. Increased spacing levels also decr eased the relative amount of growth allocated to the bole of the tree for E. urophylla and E. camaldulensis during the time period of this s tudy and increased allocation to the root system, while E. pellita sho wed relatively small changes. Allocation to the bolewood in E. urophyl la changed from 46 to 36%, in E. camaldulensis from 37 to 32%, and E. pellita from 31-34% at 3 X 1.5 vs. 4 X 3 m spacings, respectively. All ocation to the root system in E. urophylla changed from 23-30%, in E. camaldulensis from 34-45%, and E. pellita from 37-33% at 3 X 1.5 vs. 4 X 3 m spacings, respectively. Thought these results show that some of the biomass changes from species, age and spacing differences are rel ated to distribution, not total biomass production, then were signific ant differences in total biomass accumulation also. Since larger root systems may increase future yields from coppice growth, the effect of differences in allocation to the root system on future productivity ne eds to be evaluated. (C) 1998 Elsevier Science B.V.