Abstract:
Due to a lack of species-site-specific models, information about the carbon (C) stock potential
of highland bamboo in various carbon pools is limited. Thus, the objective of this study was to
develop an allometric equation for estimating highland bamboo C pools along altitudinal
gradients in Garamba forest, southern Ethiopia. Using a systematic design approach, 34 plots
were chosen and placed along a transect in the altitude range. Then, bamboo culm diameter at
breast height (DBH), height (H) and number of culms were collected. A total of 102 soil
samples were collected to determine the soil bulk density and soil organic carbon (SOC) from
three different depth classes. A composite 17 litter samples were collected. Besides, a total of
102 bamboo culms covering the full range of sizes were destructively sampled. A subsample of
bamboo biomass components and litter were taken to the laboratory to determine the C
content. Allometric equations in the form of power models were formulated for all age groups
of bamboo by evaluating the statistical relationships of measurable variables (DBH and H)
and dry total biomass (TB). The best models were validated by leave-one-out cross-validation
procedures and results were compared based on model performance statistics. The data
analysis was performed using R software. The result of the study showed significant (p<0.05)
stand density, DBH and height differences between the three altitudinal ranges. The average
culm density, DBH and height were 12,120.6 ± 3,560.5 culms ha-1
, 5.1 ± 0.9 cm and 9.2 ± 1.9
m respectively. The study also revealed that the strongest predictor variables for estimating
TB for each of the age groups was DBH (R = 0.97). Accordingly, the better performing
equations are TBage<1 = 1.005 × 0.107 × D2.167, TBage 1-3 = 1.005 × 0.198 × D2.083, TBage >3 =
1.025 × 0.155 × D2.414 and TBall age = 1.031 × 0.247 × D1.967. Except for SOC, both TB and
litter carbons showed a significant variation among altitudinal classes and increased as
altitude increases. The mean C stocks in TB, litter and SOC were 41.72 ± 18.59, 0.48 ± 0.17
and 252.60 ± 43.14 t C ha−1 respectively. The C stocks and CO2 equivalent of the Garamba
bamboo forest were found to be 293.29 ± 47.25 and 1,076.37 ± 173.42 t C ha−1, respectively.
In conclusion, the developed allometric models can be applied to estimate the biomass C
storage potential of highland bamboo forests grown in Garamba as well as elsewhere.
Garamba highland bamboo forest has significant C stock and sequestration potential.
Therefore, sustainable management of these crucial vegetation resources will enhance their
role in providing ecosystem services, including climate change mitigation.
