Tree growth and aboveground biomass in a tropical mountain forest thirty years after selective logging in Sarawak, Borneo

Tropical mountain forests are vital components of global floristic diversity as well as the hydrological cycle but have been extensively exploited. However, the impacts of human disturbances on changes in biomass and regional forest variation are not well documented in tropical mountainous regions. This study was conducted on the Payeh Maga Highland, Sarawak, Malaysia thirty years after logging at three elevational zones namely upper dipterocarp forest (UDF), lower-montane oak-laurel forest (LOF), and upper montane forest (UMF). Stand and growth dynamics were assessed for 12 months to estimate the tree growth rate and the aboveground biomass (AGB) of logged and unlogged forests at various elevations. Significant differences between logged-over and primary plots were observed in diameter at breast height (dbh) and basal area growth in the UMF. AGB recovery in the LOF plots was significantly slower that in other plot types. After three decades, the UDF and the UMF plots had AGB values similar to those of their primary plots. This study indicated that selective logging practices need to be improved to enhance the sustainability of timber production. Long-term monitoring, along with the establishment of more plots and the measurement of additional tree-competition parameters, is needed to clarify outstanding uncertainties

Tree diversity at Payeh Maga Montane Forest, Sarawak, Borneo

Tree species composition and diversity were determined at 1,600 m Payeh Maga Highland in Lawas, Sarawak, Borneo. Five study plots (20 x 20 m) were established at five transect lines (1 ha). The study shows that the forest was represented by 40 families, 68 genera and 151 species. Fagaceae represented 26 % of the families recorded, followed by Myrtaceae (16 %) and Clusiaceae (12 %) which are a typical family of montane forest in this region. Important Value Index (IV) showed Lithocarpus urceolaris as the most important species (IV=294 %), followed by Gymnostoma sumatranum (IV=273 %) and Tristaniopsis microcarpa (IV=194 %). There are no significant differences among transects for number of species and diversity indices. This forest is important for biodiversity conservation as it is as rich as those reported for lowland forests elsewhere in this region. The continued accumulation of species is an indication that this highland could support and provide habitat for larger tree species communities