PREDICTING HEIGHT GROWTH OF YOUNG PINUS KESIYA FROM SOIL-PLANT NUTRIENTS AND NEEDLE TRAITS

Abstract

Field investigatior was carried out at two provenance trial plots in southern and northern Thailand where were considerably different in elevation, rainfall, and distance from the sea. Seeds from eighteen sources were planted at the dry-highland site one year prior to planting the eleven provenances at the wet-lowland planting site. Nine of them were common to both plantations. Soil and foliage samples were collected in winter 1979, while the northern-plantation trees were four and half years old. The provenance-mean values of twenty-five variables including dbh, needle traits, foliage nutrients, and nutrients in soil were used to estimate total height dry stepwise multiple linear regression technique.

The results showed that such needle traits as dry weight, color, and length could be considered the useful tool in predicting tree height in the field. For more accuracy, either the levels of foliage nutrients or soil minerals were recommended. Based on the correlation coefficients, obtained, the order of reliable prediction was soil analysis = foliar analysis needle traits for wet site in Peninsula and soil analysis foliar analysis needle traits for dry site in the North. A combination of all parameters revealed that dbh alone accounted for 85 percent of height variability at northern plantation while needle weight accounted for 73 percent of height variation in southern plot. Tree nutrition explained 9 percent and 14 percent of the variation in height at dry site and wet site, respectively, suggesting that fertilization was not necessary for young plantation pine, especially in such developing countries as Thailand.