Comparison of soil CO2 efflux in tropical forests of different ages, Peninsular Malaysia

The forest age, environmental abiotic and biotic factors are important in controlling soil CO2 efflux in forest ecosystems, as they play an important role in soil respiration. The aim of this study was to determine the environmental factors associated with each forest age and their impact on the soil CO2 efflux rate. This study was conducted in 10-, 30-, 50- and 70-year-old recovering tropical lowland forests in Peninsular Malaysia, measuring soil CO2 efflux using the continuous open flow chamber technique connected to a multi gas-handling unit and infrared gas analyser. The forest biomass and soil properties were quantified using the Kjeldahl method and Walkley-black wet oxidation technique. The results show that soil CO2 efflux was higher in the 10-year-old forest than the older forests and lowest in the 70-year-old forest. Soil CO2 efflux ranged from 92.09 to 634.78, and 106.77 to 536.00 mg m-2 h-1 between February and June, and September and December for all forests. The higher soil CO2 efflux in the 10-year-old forest was significantly positively correlated with high soil temperature (R=0.96) compared to the spatial and temporal variation in the 30-, 50-and 70-year-old forests. The entire spatial and temporal variation in soil CO2 efflux can be largely accounted for by the soil properties, forest carbon input and environmental factors. In conclusion, soil CO2 efflux, soil properties, microclimate condition and forest biomass varies significantly with forest age. Soil CO2 efflux decreases with forest age, and increases the carbon use efficiency. The environmental factors, dominated by soil temperature, affect soil CO2 efflux substantially

Soil carbon dioxide efflux and atmospheric impact in a 10-year-old Dipterocarpus recovering lowland tropical forest, Peninsular Malaysia

The recovering logged-over forest ecosystem increases the CO2 efflux into the atmospheric carbon pool in response to environmental factors to changes in the soil temperature and moisture. These CO2 outbursts can have a marked influence on the ecosystem carbon balance and thereby affect the atmospheric carbon pool. The study was conducted in the 10-year-old logged-over forest of Sungai Menyala forest, Port Dickson, Negeri Sembilan, Malaysia. The measurements of soil CO2 efflux were conducted using the continuous open flow chamber technique connected to a multi gas-handling unit and infrared CO2/H2O gas analyser. The aim of this study was to determine the soil CO2 efflux and the environmental variables and likewise the impact of environmental factors on soil CO2 efflux. Post-hoc comparisons were made using the Tukey test (p < 0.05), and multiple linear regression to determine the impact of environmental factors on soil CO2 efflux. Soil CO2 efflux ranged from 100.22-553.40 mg m-2 h-1 with the highest efflux in the afternoon attributed to an increase in soil temperature and low moisture. A higher soil temperature and low moisture signify an influential factor as the forest is recovering from logging activity. Furthermore, the predictor environmental variables: SOC (soil organic carbon), TOC (total organic carbon), SMC (soil moisture content), Bulk Density, SOCstock (soil organic carbon stock), TAGB (total above ground carbon biomass), Below Ground Carbon Biomass, soil pH, Nitrogen to Carbon ratio account for the spatial and temporal variation in soil CO2 efflux into the atmosphere. The analysis revealed a strong correlation between soil CO2 efflux, changes soil properties and environmental factors with an R2 more than 0.80 at p < 0.01. This is proven that logging activity accounts for the changes in environmental factors to influence soil CO2 efflux rate within 10-years of logging and forest recovering