Information on tree and stand growth is essential to ensure sustained timber yield in tropical natural forests, but very little is known about stand dynamics of tropical seasonal forests, especially in the mainland Southeast Asia. Stand dynamics of seasonal evergreen forest in central Cambodia were estimated from 20 sample plots measured in 1998 and 2003. Data for all trees with diameter at breast height (DBH)≧10cm and for commercial species DBH≧10cm or DBH≧minimum diameter cutting limit (MDCL) were evaluated. In 1998, 67 species, of which 19 were commercial trees with DBH≧MDCL, were found at tree densities of 544.5 and 23.4 trees/ha, basal areas of 23.8 and 6.3m^2/ha, and stem volumes of 192.9 and 64.3m^3/ha. The mean diameter increment between 1998 and 2003 was 0.33 for all species and 0.32cm for commercial species; mean mortality rates were 2.4% and 0.5%, mean recruitment rates were 2.5% and 1.4% and volume increments were 1.09 and 0.86m^3/ha. These values are similar to those reported from tropical rain forests in Amazon and Southeast Asia. Estimated volume increment (0.86m^3/ha/year) for commercial trees with DBH≧MDCL was significantly larger than the figure (0.33m^3/ha/year) previously used in Cambodian management systems.

Information about forest biomass distribution is important for sustainable forest management and monitoring fuelwood supply. The objective of this study is to develop an accurate forest biomass map for Kampong Thom Province, Cambodia. We used a new technique (object-based approach) and a conventional technique (pixel-based approach) for the estimation of forest biomass using Landsat Enhanced Thematic Mapper Plus (ETM+). The object-based approach created segments of images, and calculated statistical and textural attributes. Our results showed that estimation accuracy of the object-based approach, with the use of band 1 and an exponential fit, was the best (R (2) = 0.76), and this accuracy was comparable to that of the pixel-based approach (R (2) = 0.67). Although several textural variables were related to forest biomass, they did not contribute significantly to improvement of estimation accuracy. However, the object-based method can be used for image segmentation so that the image objects are spectrally more homogeneous within individual regions than with their neighbors. Hence, they can be regarded as management units for policy-related spatial decisions. Therefore, it is possible to select either of the two methods depending upon what the situation demands.

This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540 plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m2/ha, the average stand volume, 217 m3/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s index. Significant negative correlations were generally found between population density surrounding clusters and tree density, basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a whole.

This study re-examined a previously published relationship between supply and demand for woodfuel at different spatial scales within Kampong Thom Province, Cambodia. We considered three different scales: The first was the whole area of the province. The second scale calculated village-scale data in zones of 1, 3, and 5km from each village and then aggregated for all villages of the province. The third scale also calculated data for the three zones at the village-scale, but the data were then aggregated according to three regional groupings based on population density and forest availability. When evaluating woodfuel supply, we excluded biomass increment of trees with diameter larger than 30cm because it was found that local people rarely collect trees larger than 30cm for fuel. On the demand side, dead wood, which was included in the previous assessment, and woodfuel obtained from non-forest sources were excluded to enable comparison of supply and demand that related only to living trees originating from forests. The re-assessment revealed large decreases in both supply and demand at each scale as compared with our previous assessment; supply reduced by 46% and demand by 36% at the whole province scale. However, the ratios of supply to demand at each scale examined were very similar for both assessments. This re-assessment therefore supports our previous findings: there is a deficiency in woodfuel resources in areas of high population density along the main road due to high woodfuel demand and a predominance of agricultural land and regrowth forest in close proximity to villages. This study underscores the usefulness of taking detailed woodfuel consumption patterns into account when assessing the impact of woodfuel demand on forests. For a more accurate assessment on the sustainability of woodfuel resources and utilization, further research is needed to project future woodfuel demand, not only for green wood from forested sources, but also for dead wood and woodfuel from non-forested sources.

To assess the sustainability of forest use for woodfuel, above ground biomass increment must be examined against woodfuel consumption. However, reliable data on the biomass increment of tropical forests are very limited. In this study, we estimated above ground forest biomass increment in Kampong Thom Province, Cambodia, using two consecutive measurements of 32 permanent sample plots in 1998 and 2000, and forest inventory data of 540 plots collected in 1997. The permanent sampling plot data were used to determine the relationship between initial biomass and subsequent biomass increment over a 2-year period. This relationship was applied to the inventory data to obtain a robust estimate of biomass increment across the major forest types for the entire province. The weighted average annual above ground biomass increment for the whole province was 4.77Mg/ha, or 2.3% of biomass. Woodfuel consumption was estimated to be about 2% of biomass increment for the province, suggesting that deficiency of woodfuel may not occur in this province. However, localized variation needs to be taken into account and there is a need to examine the effects of stand age and factors such as soil type, microtopography, and species composition on biomass increment and to consider woodfuel collection rate in specific forest areas with respect to accessibility for firewood collection.

This study adopted a GIS-based approach to reveal how the potential supply and demand of woodfuel varies at different spatial scales within Kampong Thom Province, Cambodia. We considered three different scales: the first was the whole area of the province. The second scale calculated village-scale data in zones of 1, 3 and 5 km from each village aggregated for all villages of the province. The third scale also calculated data for the three zones at the village-scale, but data were then aggregated according to three regional groupings based on population density and forest availability. The results indicated large differences in the ratio (ranging between 0.08 and 503.90) of potential supply to demand of woodfuel for the different scales examined. A deficiency of woodfuel resources was identified only in the areas along the main national road, mainly due to high woodfuel demand and predominance of agricultural land and regrowth forest in surrounding areas. This deficiency may have a negative flow-on influence to adjoining areas if they are called upon to fill the supply gap. For more accurate assessments on sustainability of woodfuel resources and use, further research is needed on the available size and species of trees used for fuel. This study indicated that use of GIS could reveal differences in the potential supply and demand of woodfuel at three different scales. Policy makers and energy planners should address such scale dependency in supply and demand relationships when preparing energy development programs.

Wbodfuel consumption rates and flow were estimated based on an interview survey of 155 households conducted in Kampong Thom Province in December 2000 and January 2001 combining with National Population Census 1998. We found that per capita woodfuel consumption rates varied in places according to heuseho]d sizes and woodfuel prices. For each district, he per capita consumption rate ebtained from the samples was normalized based on an average househeld size ef the National Populatien Census. Per capita weodfuel con$urnption rate per year of the province was 183 and 134kg for firewood and charcoal, respectively, with a mean of 131ug oven dry weod (ODwr equivalent. [[his study revealed a tota1 woodfuel consumption of 76,139 tonnes ODW equivalent for the province, of which 94.3% repre$ented by household sector, 3.2% by industrial and service sectors and 2.6% transported to Phnom Penh. 'lhese results indicate that he household sector strongly affects woodfuel flow within the whole province. IDw per capita incomes and $low ecenomic development suggest that Kampong [Ihom will not move towarcls using modern source$ of energy (kerosene, gas, or electricity) in the near future. Wbodfuels will therefore maintain its important role as a provider oi energ}L Kdywortts: firewood, charcoal, woodfuel consumption, woodfuel price, householdsize

We report details of woodfuel consumption patterns in three different village groupings classified according to population distribution and forest availability. Interview survey data collected from 240 households in 40 villages revealed large differences in woodfuel consumption patterns among the three groups. Areas with lower forest availability were associated with lower per capita woodfuel consumption, proportionately higher consumption of firewood from non-forest sources, greater distances from the village to the woodfuel source, and more species and smaller trees being utilized for firewood. The maximum size of trees used for fuel was 30cm in diameter, and about 30% of the total woodfuel used was sourced from dead wood. The survey also revealed that some species, such as Xylopia pierrei and Grewia paniculata, were favored for firewood. Respondent's answers revealed a woodfuel deficiency along the major road. While there does not appear to be any evidence that woodfuel consumption is causing deforestation, initiatives to reduce woodfuel consumption are still needed to alleviate these localized supply problems. Woodfuel consumption could be reduced by replacing the traditional “three stone fire” with more efficient types of cooking stove.