Allometric models for predicting above ground biomass and organic carbon stock of four Acacia species in the Sudanian zone of West AfricaPhilippeBayenUniversity of Ouagadougou (UNDESERT project)OuagadougouBurkina FasoMarcoSchmidtPhilippeBayenassociatedPartyAdjimaThiombianoCo-owner2015-12-03Carbon sequestration in plant is of great attention due to its concerns about global climate change. In the present investigation we developed species-specific allometric models to predict above ground biomass of Acacia gourmaensis and Acacia dudgeoni. To determine the most appropriate predictor variables in order to produce a general allometric relationship, a stepwise multiple regression technique was used. A total of one hundred and thirty (130) trees (30 for Acacia gourmaensis; 35 for Acacia dudgeoni; 33 for Acacia tortilis and 32 for Acacia nilotica) were clear-felled and immediately separated into components: stem branches and leaves. The green weight of each component sample was measured and was thereafter dried in the oven until constant weight was attained.
Allometric equations were developed for each species to estimate stem, branch, leaf and total above ground biomass. The best-fit models found for estimating tree component biomass and total above ground biomass production were of the linear form. All the components models have low Residual Standard Error (RSE), meaning the models performed well.
The aboveground biomass rate of carbon sequestered was estimated using ash method. The mean percentage of carbon content in the above ground biomass were 53,43%; for A. gourmaensis; 53,39% for A. dudgeoni; 54,75% for A. nilotica and 55,38% for A. tortilis.
The current established allometric equations may allow a rapid estimate of Acacia species above ground biomass and carbon stock in Sudanian zone and aid in a sustainable management of these species.
above-ground biomassacaciaallometric modelcarbon contentCitation of original publication required: Bayen P. and Thiombiano A. Allometric models for predicting above ground biomass and organic carbon stock of four Acacia species in the Sudanian zone of West Africa.Sahelian and North Sudanian zones of Burkina faso, West Africa-0.15920.61514.008912.03892013-10-212014-11-30GenusAcaciaPhilippeBayenUniversity of Ouagadougou (UNDESERT project)OuagadougouBurkina Fasophbayen@yahoo.fr
Sample collection and analysis of carbon content
Description: sample collection
The study was carried out from October 2013 to November 2014 using dendrometical measurements and laboratory analyses. The establishment of accurate allometric equations must clearly rely on dedicated field campaigns, in which a certain number of trees of different sizes must be selected, felled and then measured in detail.
For biomass assessment a destructive sampling of at least 30 individuals of each trees species with a wide range of diameter and height were used.
The measurement protocol for each selected individual included 6 major steps:
1. Measurements of stem girth at 20 cm above the ground, total height and crown diameters d1 and d2 (projection of the sapling above the soil, d1 being perpendicular to d2). Stem circumference and crown diameter were measured with a tape graduated in cm; height was measured with a graduated scale. Girth values were converted to diameter. Crown diameter values were used to calculate the sapling area.
2. For individual forking below 130 cm above the ground, the circumferences of all ramifications were measured. Quadratic mean was then calculated.
3. Cut each individual at the base, separated the biomass into two components, branches, twigs and leaves, and weighed these separately using a standard 50-kg scale balance.
4. Samples of leaves, twigs and branches were collected and weighed using an electronic balance to estimate the fresh mass, and subsequently dried in an oven at 105°C until a constant dry weight was obtained.
5. In order to calculate the oven dry total mass of the tree individual components, the fresh mass measured (kg) in the field was corrected for the moisture content of the sample.
6. We estimated the total dry biomass of each individual tree by summing up the masses of the components (leaves branches and trunk).
Repeat for all individual trees.
Description: Carbon content analysis
The organic carbon storage in selected individuals of Acacia species was estimated by Ash Method. The leaves, branches and trunk of each species were separated to estimate carbon. For the determination of total carbon content in each tree component (leaves, branches and trunk), composite samples were formed from the dry matter samples of this material. These samples were crushed in a cutting mill, gathering five 2g samples of each component and submitting them to analysis at the Laboratory of Plant and Soils of the University of Ouagadougou. Each 2g sample was placed in a lidless porcelain crucible and taken to a muffle furnace set at 550°C for two hours, until calcination was completed. The sample was then removed and cooled in a desiccator to be later weighed. After cooling, the crucible with ash was weighed and percentage of organic carbon calculated.