Patterns and drivers of the above- and below-ground carbon stock in Afromontane forest of southern Ethiopia: implications for climate change mitigation

Abstract

The adaptation measures in the forestry sector are essential to mitigate climate change and to support sustainable development. Reducing emissions through improved forest management is a critical approach for climate change adaptation. Several previous investigations have estimated carbon stock for forest ecosystems. However, the drivers of this function are less understood, especially in the tropical context. Hence, this investigation intended to explore the factors affecting the carbon stock potential of dry Afromontane forest in southern Ethiopia. Employing a systematic sampling system, ten transects were laid out with 125-m intervals along the altitudinal gradient. The main plots (size 20 m × 20 m each and two subplots (each: 10 m × 10 m) were laid out in the opposite corner of the main plots and in total 46 main plots and 92 subplots were used for vegetation and dead wood data collection respectively. The plots were arranged on transects at 125 m interval to measure trees and shrubs, respectively. Moreover, a total of 230 sub-sub plots (1 m × 1 m) were arranged at the four corners and in the center of the main plots to collect herbs and litters for the assessment of non-woody carbon stocks. The altitude and topographic aspects of the sample plots were recorded using Garmin GPS and Silva compass, respectively. The carbon stock was calculated using allometric equations developed for the estimation of dry Afromontane forest carbon stocks. The effect of species type, altitude, and topographic aspects on above-ground and below-ground carbon stock was analyzed by using one-way ANOVA. The results revealed that the total above-ground and belowground carbon stock of dry Afromontane forest is 1943.2 tons/ha. The carbon stock of woody species stock increased with increasing altitudinal gradient but opposite trend was found for non-woody species. Moreover, the carbon stock of both woody and non-woody species significantly varied among topographic aspects and plant family types. The carbon stock was higher for Cupressaceae (811.5 tons/ha) followed by Podocarpaceae (630.9 tons/ha). The highest carbon stock of woody biomass was recorded in the southwest aspect (663.30 tones/ha), and the lowest carbon (141.8 tons/ha) was recorded in the northwest topographic aspect. In conclusion, the environmental and vegetation structure need to be considered in devising forest conservation strategy for climate change mitigation and adaptation.