Abstract
Conversion of Natural Forest to other land uses negatively affect the biomass and soil carbon stocks. This study was carried out to investigate the impact of conversion of natural forest to rubber plantation and semi-forest coffee in terms of biomass and soil carbon stocks in Guraferda district, southern-western Ethiopia. For this study stratified systematic sampling technique was followed to establish plot sizes of 20m x 10m (200m2) across the three adjacent land uses, namely, natural forest, semi-forest coffee and rubber plantation.
A total of nested 60 sample plots (20 plots for each land use) were used to conduct woody species inventory, soil sample collection to determine soil organic carbon (SOC) and bulk density (0-30 and 30-60 cm soil layer) and litter sampling. Total biomass carbon stocks (above plus belowground) in natural forest (302.59 t ha-1) is greater than semi-forest coffee (79.96 t ha-1) and rubber plantation (43.91 t ha-1). The natural forest is significantly greater than rubber plantation and semi-forest coffee. And also, rubber plantation is significantly lower than semi-forest coffee. The mean deadwood biomass carbon of semi-forest coffee (2.64 t ha-1) was significantly higher than natural forest (1.97 t ha-1) (p <0.05). Similarly, the mean litter biomass carbon of natural forest (2.56 t ha-1) significantly higher than rubber plantation (1.85 t ha-1) and semi-forest coffee (1.31 t ha-1). The mean soil organic carbon stock was significantly highest in semi-forest coffee (112.01 t ha-1) and lowest in rubber plantation (68.24 t ha-1). It was lower in subsoil by 63.80%, 67.73% and 65.22% for natural forest, rubber plantation and semi-forest coffee respectively. The ecosystem carbon stocks (biomass and soil) were 391.49 t ha-1, 112.15 t ha-1 and 191.97 t ha-1 in natural forest, rubber plantation and semi-forest coffee xvi respectively. The present study revealed that conversion of natural forest to rubber plantation and semi-forest coffee significantly reduced the carbon stocks both in the biomass and soil. Therefore, it is very clear that there is a need for conservation of the existing forest through introduction of sustainable forest management approach to maintain climate mitigation potential while ensuring the economic benefits.
Keywords: Deadwood, Deforestation, Greenhouse gas removal, Litter carbon, Mitigation