Effects of 50 years of selective logging on demography of trees in a Malaysian lowland forest
Species specific tree performance (growth, mortality, and recruitment rates) and population growth rate in a logged forest that was selectively logged in 1958 were compared with those in a primary forest using 10-year forest demographic data (1998–2008) in the Pasoh Forest Reserve in Malaysia. The forests differed in forest structure and the logged forest had brighter understory light conditions than the primary forest. The underlying hypothesis of this study is that the forest structural differences caused by selective logging 50 years ago affects tree performance and demography through increasing forest light environments. Species studied showed significantly faster dbh (diameter-at-breast-height) growth rate in the logged forest than in the primary forest. There was very little difference in mortality rates between the logged and primary forests. Recruitment rates in the logged forest were significantly lower than those in the primary forest. Consequently, population growth rates were significantly higher in the primary forest. These findings support our hypothesis and imply that selective logging approximately 50 years ago was still influencing tree performance and demography of the forest. In the logged forest, populations of early successional species declined more than the other species, although this was not the case in the primary forest. Although there still remains a possibility that the decline was due to a drought event and thus was just temporal, this suggests the species composition of the logged forest is still changing and gaining additional late successional species. Therefore, the logged forest was still in secondary succession after selective logging. We should note that logging cycles shorter than 50 years may not be enough long to recover original species composition before logging.