Abstract
Eucalyptus plantations on farm woodlot system represent a short term and cost efficient alternative for sequestrating CO2 from the atmosphere while sustainably meeting the wood demand of local communities. Despite the known potential of fast growing trees species to store carbon in their biomass, there are relatively few studies indicating precise estimates of carbon stocks in plantations of such species as Eucalypts, especially those on farmers' woodlots.
This study evaluated C pools in soil and tree biomass in woodlots of Eucalyptus camaldulensis Dehnh. and their management practices in Damot Sore district. Three kebeles were randomly selected from the district since all kebeles within the district were dominated by intensive plantation of privately owned Eucalyptus camaldulensis woodlots. Reconnaissance surveys were carried out on farmers' Eucalyptus woodlots in the study kebeles prior to data collection to identify different sizes of representative woodlots with Development Agents (DAs). A total of 62 plots (10x10m) were established on woodlots of randomly selected households across woodlot size classes based on their proportional representation (14 for large, 26 for medium, 22 for small) and the field data was collected by measuring trees with a DBH of 3cm and total tree height. Already developed allometric equations were used for biomass estimation. In each main plot, three 1m×1m subplots were used to collect litter samples and soil samples for SOC estimation were collected using a core sampler from five sampling points using 'X' design with two replications. A total of 248 samples (i.e. 124 for SOC and 124 for bulk density) from two depths were sampled. All statistical analysis was made using statistical software of SPSS (version 16). The results revealed that, the mean total carbon stock (biomass plus soil, 0-60cm) was significantly higher in E. camaldulensis woodlots of large and small households (respectively 97.9 ± 9.17 and 90 ± 7.06Mg C ha-1) than medium sized households (83.29 ± 13 Mg C ha-1). The soil organic carbon (SOC) accounted 72% for large, 84% for medium and 88% for small households. Carbon stocks (biomass and soil) were strongly correlated (Spearman r=0.753 and 0.864, p=0.001) with woodlot size classes of households. Pruning, thinning, composting, weeding and cultivation, burning stump after harvest, application of commercial fertilizer, and watering were the most common management practices that affect carbon stocks in both biomass and soil in the area. This study concluded that the carbon stock value of E. camaldulensis woodlots is large , and the carbon storage in different carbon pools of the system varies with different size classes of the woodlot. Therefore, climate change mitigation efforts on farmers Eucalyptus woodlots should also be considered the factors other than size of woodlot and management practices affecting carbon accumulation of the system.
Keywords: Biomass carbon; soil carbon; carbon sequestration; plantations; climate change
