Abstract:We investigated the capabilities of a canopy height model (CHM) derived from aerial photographs using the Structure from Motion (SfM) approach to estimate aboveground biomass (AGB) in a tropical forest. Aerial photographs and airborne Light Detection and Ranging (LiDAR) data were simultaneously acquired under leaf-on canopy conditions. A 3D point cloud was generated from aerial photographs using the SfM approach and converted to a digital surface model (DSMP). We also created a DSM from airborne LiDAR data (DSML). From each of DSMP and DSML, we constructed digital terrain models (DTM), which are DTMP and DTML, respectively. We created four CHMs, which were calculated from (1) DSMP and DTMP (CHMPP); (2) DSMP and DTML (CHMPL); (3) DSML and DTMP (CHMLP); and (4) DSML and DTML (CHMLL). Then, we estimated AGB using these CHMs. The model using CHMLL yielded the highest accuracy in four CHMs (R 2 = 0.94) and was comparable to the model using CHMPL (R 2 = 0.93). The model using CHMPP yielded the lowest accuracy (R 2 = 0.79). In conclusion, AGB can be estimated from CHM derived from aerial photographs using the SfM approach in the tropics. However, to accurately estimate AGB, we need a more accurate DTM than the DTM derived from aerial photographs using the SfM approach.

Biomass estimations in tropical peat swamp forests are quite complex when hollow trees are frequently found due to the unavailability of data on hollow size and the limited data on accurate measures of biomass. Destructive samplings were done for both above-(AGB) and belowground biomass (BGB) and hollow sizes of remained trees at a logged-over peat swamp forest in Sarawak, Malaysia. Subsequently, allometric equations taking hollows into account for both the above-and belowground biomass of tropical peat swamp forests were also being developed. It was observed that these were hollows in Shorea albida and Combretocarpus rotundatus trees with diameters at breast height (DBH) exceeding 40 cm; S. albida is a dominant or co-dominant species, and C. rotundatus grows in peat swamp forests throughout Sarawak. The hollow volumes ranged from 0.23 to 1.08 m 3 , and occupied 42.3% of stem volume on average. The larger biomass produced by previous allometric models were partially due to the presence of hollows. Thus, new models for estimating both AGB and BGB were developed that included one (only DBH), two (DBH and height [H]

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expanding the potential scope of concepts by including forest degradation and acknowledging the importance of conservation, the sustainable management of forests and the enhancement of forest carbon stocks (REDD plus) 15 . Methodological guidance is requested by developing country parties for activities relating to reducing emissions from deforestation and forest degradation (Decision 4/CP.15) 15 in order to establish robust and transparent na- IntroductionDeforestation in the tropics will remain a major source of carbon emissions in the coming decades 1 . International discussion has focused on mechanisms providing economic incentives for reducing CO 2 emissions from deforestation in developing countries (REDD) 14 and JARQ 46 (2), 187 -192 (2012) AbstractAs a feasibility study for applying a simplified method to estimate CO 2 emissions from deforestation and forest degradation in tropical forests, we estimated the nationwide forest tree biomass carbon stock using data from 100 permanent sampling plots (PSPs) set by the Forestry Administration, Cambodia in seasonal forests in Cambodia. Averaged tree carbon stocks and SE-Standard error were at 158.8 ± 7.3 Mg C ha -1 for evergreen and semi-evergreen forests and 55.2 ± 6.9 Mg C ha -1 for deciduous forests in 1998 (the first census) and for the second census in 2000-2001, 163.8 ± 7.8 Mg C ha -1 and 56.2 ± 6.7 Mg C ha -1 , respectively. The averaged tree biomass carbon stock differed significantly between the two forest types. Using the forest cover for 2006 and the averaged carbon stock for 2000-2001, the national-level forest tree carbon stock in the early to mid-2000s was estimated at 824.2 ± 39.2 Tg C for evergreen forests and 263.9 ± 31.3 Tg C for deciduous forests, and 1,088.1 ± 50.2 Tg C in total. By repeating this calculation for all forest areas by remote sensing and averaged tree carbon stock via ground-based measurement with PSPs, we could monitor the total tree carbon stock in nationwide forests in Cambodia. We also presented the possible reasons for uncertainty related to the present tree biomass carbon stock of forests and recommendations in order to improve the accuracy of the carbon stock using PSP systems in Cambodia.