Forest floor carbon stocks, which include different components of litter, hemic and sapric materials, have not been empirically quantified in tropical montane forest, although they influence soil carbon (C) pools. To date, the contribution of arbuscular mycorrhizae in C sequestration potentials in tropical montane forests have not been clearly investigated. This study determined the amount of C stocks in the different decomposing layers of forest floor, mainly litter, hemic and sapric materials. The abundance of arbuscular mycorrhizal root colonisation differed among forest floor fractions. Forest floor was measured for depth, area density, dry mass and carbon fraction separately in Sungai Kial Forest Reserve, Pahang, Malaysia to calculate C stocks. Percentages of root colonisation in the hemic and sapric materials were investigated. The results showed that forest floor C stocks were significantly higher in hemic (5 Mg C ha −1) and sapric (7.7 Mg C ha −1) compared with the litter fragments (1.5 Mg C ha −1). Mycorrhizal root colonisation was significantly higher (75%) in the toeslope compared with the summit area in the hemic materials. Segregation of forest floor layers provided greater accuracy in forest floor C stocks reporting.

Forest plantations are seen as a potential alternative to natural forest for timber supply. Leaders in forest plantation development include China, India, the Russian Federation, United States and Japan, which accounted for 65% of planted area in 2000. Other countries with increasing forest plantation development include Malaysia. Initiatives for large-scale forest plantation establishment in Malaysia started with an envisaged production of pulp, then second, an effort to augment timber supply with selected fast-growing species within 15 years, and third, to establish 375,000 ha of commercial forest plantation in stages. The first two initiatives ended up as failures due to shortcomings such as seed viability, mismatched downstream industry to the species planted and logistic unfeasibility. The third initiative looks promising as plantations are owned by the industry with the government providing loans and technical assistance. One industry has already entered its third rotation. Large hectarages of land are an advantage to have harvesting in perpetuity based on seven-year rotations. Choosing the right species that matches industry needs, improved planting materials and correct silvicultural practices are important factors, while having integrated downstream processing is an advantage.

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Soil respiration is the second largest flux in the carbon (C) cycle, contributing close to 40% of annual atmospheric input. It was hypothesised that partitioning total soil respiration (Rs) and heterotrophic respiration (Rh) during wet and dry seasons will improve understanding on the effects of environmental variables, organic detritus input and decomposition on soil respiration trends in the tropics. A trenching experiment was conducted to quantify Rs and Rh over a period of 30 months, and climatic variables, soil bulk density, water and air filled pore space, fine root biomass, decomposition ratio and litterfall coinciding with soil respiration measurements were recorded using chamber methods. The Rs was significantly different across time where elevated levels (518.60-784.08 mg CO 2 m -2 h -1 ) were observed during wet season but Rh did not differ. The Rh contributed a larger portion (73-90%) to Rs compared to autotrophic respiration (Ra). Soil temperatures and relative humidity were significantly different in Rs and Rh plots. Wet season also significantly elevated fine root biomass (222.93-237.96 g m -2 ), fine root decomposition ratio (0.49) and litterfall (304.64 g m -2 ) that contributed to Rs. It was concluded that climatic and primary productivity variables affect Rs and Rh in a tropical forest ecosystem. However, long term temporal and spatial observations are necessary to improve the understanding of forecast soil CO 2 sequestration dynamics in a changing environment.