Topography of a Large-Scale Research Plot Established within a Tropical Rain Forest at Lambir, Sarawak.

Abstract

A large-scale research plot 52 ha in area was recently established at the Lambir Hills for a long-term ecological research of tropical rain forest in Sarawak, East Malaysia. The work for plot demarcation including a topography survey was initiated in November 1990 and continued till March 1992. Electronic tacheometers with automatic distance meters were adopted to built the plot with reliable accuracy on steep and complex slopes. The plot with an area of 500 m × 1040 m was divided into 1300 quadrats of 20 m × 20 m and further divided into 20,800 subquadrats of 5 m × 5 m, by setting landmarks at all the comers of quadrats and subquadrats. The compass directions and zenith angles to elevation at the base of respective landmarks were carefully surveyed with tacheometers by following conventional land survey methods. The topographical data thus obtained were transformed into altitude values at each landmark. The altitude difference between the lowest and highest points in the plot was ca. 150 m. A topography map was drawn by using these altitude data. Furthermore, a geometrical plane covering each of 1,300 quadrats was numerically determined to calculate the detailed statistics of topographic variables, such as the altitude, direction, angle, and convexity of slopes. The statistics of these variables and their distribution maps within the plot suggested the steep, undulating, and complex slope-topography of the plot. These topographic features seemed to result in the fragmentation of plant habitats and might be strongly combined with a rich flora of the Lambir rain forest.