ASSESSMENT OF CARBON STOCKS UNDER DIFFERENT LAND COVER TYPES IN HALLAYDEGHE WILDLIFE RESERVE, NORTHEASTERN ETHIOPIA

Abstract

Hallaydeghe Wildlife Reserve is characterized by different land cover classes with semi-arid to arid climatic conditions. This study has analyzed the total carbon stocks and changes in the land cover during the 1986-2019 period of the study area. In addition, the effect of land cover type on carbon stocks under three different vegetation types namely woodland, grassland, and bushland has been evaluated. Screen digitization was performed on landsat images for the years 1986, 2003 and 2019 to produce land cover classes. Final land cover maps were prepared using ArcGIS 10.3 and ERDAS Imagine softwares following field verification and accuracy assessment. Future land use changes are simulated to the year 2035 using the CA-Markov model using IDRIS 17.0 software. The total carbon stocks were analyzed from five different carbon pools namely aboveground, belowground, dead wood, soil and litter carbon. Soil samples were collected from three different depths i.e. 0-10cm, 10-20cm and 20-30cm. Data of woody species of trees and shrubs, litter, and soils were collected using the random systematic sampling techniques. A plot of 20m x 20m for trees, replicated three times was used within three different habitat types. Sub-plots of 5m x 5m for shrubs, and 1m x 1m for herbs, litter biomass and soil samples, four at each corner and one at the center were used. Aboveground biomass carbon (AGC), belowground biomass carbon (BGC), litter biomass carbon (LC), dead wood carbon (DWC), soil organic carbon (SOC), and total carbon stock (TC) were estimated using allometric equations. Woodland was the dominant land cover type, sequestering more carbon as compared to the other two land cover types. Land use/land cover analysis during 1986-2019, showed that land cover changes occurred throughout the period. During the whole period (1986-2019), woodland increased by 57.94% whereas grassland and bushland decreased by 6.86% and 10.51%, respectively. Based on CA-Markov model, predicted land cover maps for the year 2035 were generated. An expected increase in bushland (40.68%), decrease in woodland and grassland, (52.61 and 43.78%, respectively) and the emergence of a new land cover type, bareland, by 2035 is expected from the prediction of future land cover. The total carbon stocks for woodland, grassland, and bushland were 35.94±6.63, 22.55±3.35, and 23.65±3.25 tons of carbon per hectare, respectively, which showed a significant difference. (P < 0.05). The largest carbon pool in all the three land cover types was SOC pool contributing the highest amount of carbon i.e. 68.76±11.35 tons C per ha. The vegetation type in the study area is shifting from bushland and grassland to woodland, which will affect the food and nutrition status of the grevy’s zebra which is the key species of the wildlife reserve. Land use/land cover management is a vital measure for protection of present carbon stocks. Therefore, sustainable management and climate smart practices such as community based conservation should be put into consideration in order to maintain and protect the ecosystem health and enhance the carbon sequestration potential of the area