Floristic composition and carbon pools along altitudinal gradient: the case of gara–muktar forest, west hararghe zone, eastern Ethiopia

Abstract

Forests play vital role in combating climate change through carbon sequestration in the atmosphere and serving as a carbon sink in the form of carbon pool systems of forest ecosystems. The species composition and carbon stock in the different carbon pools and analysis of the influence of the environmental gradients were studied by systematic sampling method collecting data in thirty-six quadrant plots of 20x20m each distributed along transect lines. Diameter at breast ≥5cm and total height measured for each tree in the main plot. Above and below ground biomass was estimated using allometric equation, while the litter carbon was estimated by taking 50% of dry biomass as carbon. Soil sample was collected using auguring method and analyzed following Walkley-Black method, while bulk density was performed using core sampling method. The data was analyzed was performed using one way ANOVA of R software. The carbon stocks in aboveground, belowground, litter biomass and soil organic carbon showed distinct variation along environmental gradients. The aboveground and below ground carbon stock was showed a decreasing trend along with increasing altitude, while soil organic carbon and liter carbon showed increasing trend along with increasing in altitude. The mean total above and below ground carbon stocks were 156.60t C ha-1 and 31.32t C ha-1 respectively whereas, litter carbon and soil organic carbon stocks were 2.72t C ha-1 and 125.86t C ha-1 (up to 30cm depth) respectively. The mean total carbon stock density in all carbon pool of Gara-Mukitar forest was found to be 316.6±67.15t C ha-1 from which 49.5% of carbon was contained in the above ground biomass, 9.9% in below ground biomass, 0.9% in litter carbon and 39.8% was stored in soil organic carbon (0-30cm depth). The analysis of carbon stock variation of different carbon pools along altitude of the forest showed a significant variation, whereas the above and belowground carbon stock variation with slope gradient was also significant except soil organic carbon and liter carbon. It result concluded that Gara-muktar Forest is a reservoir of high carbon, since it has a good capacity to sink carbon from the atmosphere having positive role in reduction of greenhouse gases and in contributing to climate change mitigation. Therefore, to enhance the carbon stock of forest in a sustainable way, it should be supported with proper community based forest management system.