Spatial distribution of ulin (Eusideroxylon zwageri Teijsm. & Binnend.) based on slope position and its stand structure in the forest area of tabalong district

Abstract

Forest resources in Tabalong District has been degraded, proved by the fact that Ulin trees (Eusideroxylon zwageri) are difficult to be found. Ulin is in the status of endangered species, thus it must be protected and under the development efforts. Therefore, it needs information on Ulin spatial distribution based on the slope position and its current stand structure. The characteristic of the site along the slopes from the valley to the top position depends on the ecological factors. The purpose of this study was to analysis the Ulin spatial distribution based on the slope position and its stand structure. It used overlay method for the distribution of Ulin by spatial data with slope position, to be analyzed further by tabulation method. Both primary and secondary data showed that the number of Ulin found on the upper slope to the lower slope is increased; the remaining 17% found in upper slopes. Ulin stand structure in the study area did not follow the reverse-J shaped structure of the natural forest stand structure. The primary data showed that Ulin trees with diameters 20-39 cm only found in 18.8%, Ulin with diameter > 40 cm only found in 0.6%. The secondary data showed that Ulin with diameter < 40 cm found for 80.3%, while only 19.7% for diameter of > 40 cm. This means Ulin with a diameter of ≥ 40 cm has generally been cut down.