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Abstract

Growth performance of nine native tropical tree species planted on mine spoil under two levels of NPK treatment was studied by measuring height and diameter. Of the nine species, four were leguminous. All the tree species responded positively to NPK fertilization; however, the impact on leguminous species was little compared to non-leguminous species. In general, the height/diameter ratio decreased from control to full-dose NPK treatment, suggesting that nutrient enrichment influenced the resource allocation pattern such that the diameter growth was favored. The log-transformed height-diameter relationships were significant for the three treatments in all the tree species. The slopes (β) obtained were compared with three different models of tree growth (i.e., elastic similarity, geometric similarity, and constant stress). Acacia catechu, Dalbergia sissoo, Gmelina arborea, and Azadirachta indica fitted the elastic similarity model, whereas Pongamia pinnata and Phyllanthus emblica followed the constant stress model. Tectona grandis was the only species that followed the geometric similarity model. In Albizia lebbeck and Terminalia bellirica, the β values were considerably lower (i.e., below 0.5) and these two species did not fit any of the three models of tree growth. In several cases the β values were considerably influenced by nutrient enrichment.

Key words: chemical fertilization, coal mine spoil, growth response, tree structure, tree volume, tropical tree species, height/diameter ratio.