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A minimum-distance boundary method that will minimize the sum of distances between measured points and a fitted self-thinning lines on log-log coordinates of stand density and quadratic mean diameter was proposed in order to estimate the maximum size density line: an upper boundary of self-thinning line. The lines for A. mangium were inferred with this method using data in two areas of unthinned plantations in South Sumatra, Indonesia. Slopes of the lines were deduced as Ϫ1.63 and Ϫ1.67 within the range of 10-21 cm of quadratic mean dbh. The intensity of self-thinning was examined as a rate of reduction of density in relation to dbh increment. The rates were found to be higher than the slopes in the range close to the maximum line; hence the lines inferred in this study were likely existent. Maximum basal area deduced from the size-density line was 28-30 m 2 /ha at 12 cm of dbh and then it increased up to 34-37 m 2 /ha at 20 cm of dbh.

The first generation genetic gains in four secondgeneration seedling seed orchards of Eucalyptus pellita established at two locations in Indonesia (Kalimantan and Sumatra) were examined by analyzing data on the height, diameter and stem form of the trees during years 1 to 3. The seed orchards each consisted of 60 open-pollinated families: 48-49 families from first-generation plus trees (improved population) and 11-12 families from natural forest (unimproved population). The realized gains for height and diameter were ca. 16 and 19%, respectively. These gains were highly significant and consistent, irrespective of age and location. However, the gains in stem form were much lower (4%) in Kalimantan than in Sumatra (21%) and only significant in the latter, possibly because of the more intensive silvicultural management regimes at the Sumatran sites. The results confirmed that the first-generation tree improvement program for E. pellita has been effective in Indonesia, and that it should provide improved seeds for operational plantation, thus raising their productivity.