COMPARISON OF VARIED FOREST INVENTORY METHODS AND OPERATING PROCEDURES FOR ESTIMATING ABOVE-GROUND BIOMASS IN MALAWI’S MIOMBO WOODLANDS

This study assessed forest inventory methods and standard operating procedures (SOPs) for estimating above-ground biomass (AGB) and carbon, as employed in the key REDD+ Miombo Forest Reserves of Malawi. Analysis of Variance statistical technique was applied to investigate the following methods and SOPs: (i) allometry, (ii) sample plot configuration, and (iii) dendrometric measurements. Results indicate that the allometric equations parameter significantly (P<0.001) affected the AGB estimations and was the highest contributor (97.95%) of the total variation. Malawi’s specific allometry provided the highest AGB estimate (113.08±1.56 t/ha). In contrast, the Pan-Tropical/generalized allometric models substantially underestimated AGB within the range of 16.7-67.9%. Furthermore, the findings demonstrate that the use of varied sampling plot sizes significantly (P<0.001) affected the estimates of AGB. However, the plot size parameter contributed only 1.65% to the total variation. The 20m radius plot size registered the highest AGB (75.31±0.77 t/ha) compared to the 17.84m radius plot (66.12±1.61 t/ha). This signifies that the plot size of 17.84m radius underestimated the AGB by 12.2%. However, results on dendrometric measurements showed no significant (P>0.05) differences in the AGB estimates between the use of diameter tape (D-tape) and calliper in measuring dbh of individual trees despite the former yielding higher estimates of AGB (74.65±0.93 t/ha) than the latter (72.53±0.98 t/ha). This demonstrates that the use of calliper in measuring dbh underestimated AGB t/ha by only 2.8% compared to the use of D-tape. Therefore, the study recommends; employment of local allometry, adoption of a circular sampling design of 20m radius, and consistent use of D-tape in measuring dbh for AGB in Malawi’s Miombo Woodlands. In conclusion, incorporation of these changes is envisaged to facilitate quick realisation of Malawi’s REDD+ carbon payments, smooth running of the National Forest Inventory system, robust implementation and global recognition of the REDD+ efforts.