MINERAL-COMPOSITION OF LEAVES AND BARK IN ALUMINUM ACCUMULATORS IN A TROPICAL RAIN-FOREST IN INDONESIA

Mineral composition including Al, Ca, Mg, P, S, and Si and relationshi ps between Al and other elements such as Ca, Mg, P, S, and Si in leave s and bark of trees in a tropical rain forest in West Sumatra were stu died. Sixty five tree species and 12 unidentified trees were referred to as Al accumulators based on Chenery's definition (more than 1 g kg( -1) Al in leaves). For most of the Al accumulators, Al concentration i n leaves was higher than in bark. However, some members of Euphorbiace ae, Melastomataceae, and Ulmaceae families showed a reverse trend. Mos t of the non-accumulators also showed a higher Al concentration in bar k than in leaves. These results indicated that there was a difference in the mechanism of Al accumulation in tree bodies. Some of the Al acc umulators showed an extremely high Al concentration (more than 10 g kg (-1)) not only in the mature leaves, but also in the new leaves. Analy sis of the relationships between the concentration of Al and the other 5 elements in leaves, revealed that Al accumulators could be separate d into two groups at the Al concentration of 3 g kg(-1). This finding suggested that new criteria based on Al concentration (greater than or equal to 3 g kg(-1)) or Al/Ca ratio in leaves could be proposed in or der to define Al accumulators, apart from Chenery's criterion. Alumini um accumulators with an Al concentration in leaves lower than 3 g kg(- 1) (Al accumulators <3 g kg(-1)) showed the same trend as the non-accu mulators in terms of these elemental relationships, while Al accumulat ors with an Al concentration in leaves higher than 3 g kg(-1) (AI accu mulators greater than or equal to 3 g kg(-1)) showed a different trend from the non-accumulators. The Al accumulators greater than or equal to 3 g kg(-1) and the other trees (Al accumulators <3 g kg(-1) and non -accumulators) showed separately positive correlations between the con centrations of Al and Ca (or Mg) in the leaves. This observation seems to be opposite to general findings in plant nutrition, i.e. inhibitio n of Ca or Mg uptake by Al.,A positive correlation between Al and S wa s also observed for all the trees. The Al accumulators greater than or equal to 3 g kg(-1) showed positive correlations between the concentr ations of Al and P (or Si) in the leaves, unlike the other trees. Thes e findings suggested that Al stimulated P, S, or Si accumulation in le aves or Al was transported with P, S, or Si for the Al accumulators gr eater than or equal to 3 g kg(-1). No negative relationships between A l and the other 5 elements in the leaves were observed for the Al accu mulators greater than or equal to 3 g kg(-1).