Spatial Distribution Pattern of Trees in Relation to Soil Edaphic Status in Tropical Rain Forest in West Sumatra, Indonesia II. Distribution of Non-Accumulating Trees.

Concentrations of 15 mineral elements - S, K, Al, Ca, Mg, Cl, Si, Na, B, Cu, Fe, Mn, P, Sr, and Zn - appearing in 457 bark samples of trees in a 1 ha observation plot in West Sumatra, Indonesia, were analyzed. Based on the analytical results, an elemental non-accumulating tree was defined for each element as a tree with its concentration of the element in question within the bottom 5% (in this case 23 trees) of the 457 samples, irrespective of tree species. The relationships between the spatial distribution of the non-accumulating trees and the soil edaphic status at two depths (0-5 cm and 5-15 cm) were studied. The non-accumulating trees of K, Al, Ca, Na, B, Cu, Mn, Sr and Zn tended to be distributed in areas where the concentration of those extractable elements in the soil was low. This indicates that a positive association between the soil edaphic status and the nutritional characteristics of the tree bark existed, as demonstrated by the distribution pattern of these non-accumulating trees. On the other hand, the distribution of the non-accumulating trees of S, Mg, Si, Fe and P was rather independent of the soil edaphic status of those elements, suggesting that the distribution of these non-accumulating trees was affected more by genetic factors or by environmental factors other than the soil edaphic status of those elements. The relationship between the elemental concentrations in the bark and in the soil was also studied. A significant positive correlation was observed for K, Mg, Na and Sr, and a significant negative correlation was observed for B, Mn and P among the 457 trees, suggesting that those elemental concentrations in the bark were strongly related to the soil edaphic status. The non-accumulating trees of K, Na and Sr were distributed in the areas with the low and narrow elemental concentration range in soil, suggesting that the low edaphic levels seemed to strongly contribute to the low concentration level in the bark. However, in terms of the other accumulating trees and non-accumulating trees, the concentration levels in the bark were considered to be regulated not only by the soil edaphic status, but also by the tree genetic characteristics.