West Katimantan has about 10 species of Shorea cal]ed as tengkawang whose fruits are economically useful as source of fat. The fruits were collected from natural and semi-natural forests and plantations. We made eight plots in tengkawang forests in 1991 to study the change of forests by the human activity. In Ngabang which had been the capital city of old Landak Kingdom, the king made two plantations of ca. 1 krn² about 100 year ago. In tengkawang species, S. stenoptera was mainly planted on flat bank near river, and S, amptexicautis, and S. pinanga was on upper slope. They reached 125 cm in DBH and 49m in height. The average diameter increment of tengkawang from 1991 to 1994 was 0.28 (± 0.32 SD) cm/yr. Two rubber tree species, Hevea brasiliensis and Palaquium gutta were p:anted under the canopy of tengkawangs of fiat bank and slope, respective]y. The plot had 123 species of wild and cultivated trees (DBH > 4.8cm) in 1 ha, and the diversity was similar to the natural tengkawang forest.
On river banks of small stream near a village Muarailai, semi-natural tengkawang forests were found. Large trees reached 186 cm in DBH. People had cut useless trees and planted useful trees such as Hevea and Durio under the canopy of tengkawang. Along the Daid River, tengkawang forest remained nearly natural condition. The forest structure was similar to semi-natural forest but no p]anted trees except one escaped shrub Bullucia pentamera introduced from Latin America. The common tengkawang, S stenoptera dominated exclusively on flat river banks of sandy soil and the diversity was not so high. Thwe ether dipterocarp forest on slope had higher diversity,