Logging History and Its Impact on Forest Structure and Species Composition in the Pasoh Forest Reserve — Implications for the Sustainable Management of Natural Resources and Landscapes

Abstract

A part of the Pasoh Forest Reserve (Pasoh FR) was once logged under a logging regime called the Malayan Uniform System (MUS) in the 1950s. The core area of the reserve is a residual unlogged (primary) forest that shows the typical structure and species composition of lowland dipterocarp forest; the logged area of the reserve is also a relict area of regenerating lowland forest. In this chapter, we review and summarize previous studies of logging impacts on the forest structure and total aboveground biomass by comparing the primary and regenerating forests of this reserve. We also studied landscape changes in the Pasoh Forest Region in order to discuss the relationship between logging history in this region and its impacts on the forest. From a chronological analysis of the changes in land use in this region, we found that ca. 50% of the forested area had been converted to either oil palm or rubber plantations from 1971 to 1996. Almost all of the lowland dipterocarp forest that had developed in the flat and alluvial topography had vanished from this region, except in the Pasoh FR. Thus, very little area was left to be managed by the MUS approach, which was originally designed for extracting timber with a longer logging cycle (>70 years) in this type of forest. By examining the canopy and stand structure and the species composition of these forests, we found a greater density of semi-medium (6-10 cm in diameter) and medium trees (10–30 cm), a higher density of canopy-forming trees with relatively smaller crowns, and a higher density of non-commercial canopy-forming trees in the regenerating forest. These findings suggest that the MUS was incompletely implemented, since this system originally aimed to encourage the development of a uniform forest structure with a large number of sound commercial timber trees by removing noncommercial trees. Owing to the high density of canopy-forming trees, which probably resulted from incomplete post-logging thinning and vegetation-control operations, structural development was delayed in the regenerating forest. In addition, the species composition and the distribution of wildlife in the regenerating forest differed from those in the primary forest. We also found that the total aboveground biomass in the regenerating forest had not fully recovered to the level in the primary forest even 40 years after logging. We suggest that “follow-up operations” should be undertaken, with a special concern for encouraging the structural development of the stand, which we consider to be crucial for ecologically sustainable management