Abstract
The regeneration of natural forests is essential for maintaining forest ecosystem functioning, which is globally threatened by human disturbance. The important climate-related functions of the regenerated forest ecosystem are carbon sequestration, regulating the global carbon cycle, and climate change mitigation. About 80% of the terrestrial carbon is stored as forest biomass and soil organic carbon.
Deforestation and forest degradation show an alarming high, mainly due to the conversion of natural forest to commercial and cereal crop production. By considering this issue this study was conducted with the aim to assess the effect of coffee expansion on regeneration and carbon stock of the natural forest ecosystem in Gidame woreda. The primary data were collected from field forest and soil inventories. The study site was stratified in two strata: undisturbed natural forest and disturbed coffee forest. In the investigation of regeneration status and biomass carbon stock estimation, a total of 71 nested square sample plot was determined, proportionally allocated (29 for undisturbed and 42 for disturbed/coffee forest) and randomly distributed within each stratum. In both cases, seedlings and saplings were counted and recorded. The diameter at breast height and tree height were measured; litter sample was collected by harvesting and weighing technique. A total of 72 composite soil samples were collected from proportionally and randomly selected 24 sample plots; 10 from undisturbed natural forest and 14 from the disturbed coffee forest for SOC quantification in three layers(0-15 cm, 16-30 cm, and 31-45 cm). From forest inventory data, the aboveground biomass carbon stock was estimated by using allometric equations. The below-ground biomass carbon stock was derived from the aboveground carbon stock. The results showed that the regeneration of undisturbed natural forest was “good” as the present in seedlings density greater than saplings greater than mature plants. The enumerated mean densities of seedlings, saplings, and mature trees in undisturbed natural forest were 4583±67plants/ha, 3287 ±35 plants/ha, and 740 ± 14 stems/ha respectively. In the disturbed coffee forest, the density of seedlings less than saplings less than mature plants showed poor regeneration due to coffee management activities in the natural forests. The mean densities of seedlings, saplings, and mature trees in the disturbed coffee forest were 237±7.3plants/ha, 314±73 plants/ha, and 344 ±15 stems/ha respectively. The seedlings, saplings, and mature plant species densities in the disturbed coffee forest were decreased by 94.83%, 90.45%, and 53.51% respectively as compared to undisturbed natural forest. The biomass carbon stock was298.758± 9.4 tc/ha for undisturbed natural forest and199.895 ± 11tc/ha for disturbedcoffee forest and the difference is statistically significant asp<0.05. This revealed that the disturbance of this natural forest ecosystem, which is associated with the conversion of natural forest to the coffee cultivation area, resulted in the loss of 33.09% of the biomass carbon stock. The SOC is 148.40 ± 12 tc/ha for undisturbed forest and 153.80 ± 4.30 tc/ha for disturbed coffee forest has no significant difference asp>0.05. Therefore, maintaining the regeneration and biomass carbon sequestration potential of this natural forest ecosystem should be required through the implementation of different conservation mechanisms.
Keywords/ Phrases: coffee forest, coffee management, disturbed forest, forest degradation, undisturbed forest
