Abstract
Human-made landscape modification including coffee management and intensification in natural forest has been playing incomparable roles in affecting forest carbon (C) stock potential in western and southwestern Ethiopia which is not studied well. By considering this issue, the current study was conducted with the aim to evaluate the C stock changes in different C pools as a result of conversion of natural forest to coffee-based forest at Anfilo district, western Ethiopia, 642 km west of Addis Ababa.
For the present study, two adjacent land uses, protected natural forest (PNF) (1,576 ha) and forest with coffee (FWC) (2,364 ha) were considered. In light of this, primary data were collected from forest and soil. A total of 60 square plots having 35mx35m size each with nested plots of (25mx25m, 7mx7m and 1mx1m) were laid systematically and allocated proportionally for the two sites (24 for PNF and 36 for FWC). Vegetation parameters like DBH, Height and specific wood density were considered for aboveground biomass (AGB) estimation. Within each nested sample plots inventory of woody and non-woody species with the DBH of > 5 cm , litter and herb, dead woods and soil samples (0–20, 20–40 cm layers) were collected. Similarly, a total of 120 soil samples (60 for C content and 60 for bulk density) were collected and taken to laboratory for the determination of C content and bulk density. The allometric equation of Chave et al. (2014) and Walkley-Black method were used to estimate aboveground biomass and soil C stock respectively. Belowground biomass was estimated using root: shoot biomass ratios (0.27:1) from AGB. Default value of 0.47 (47%) was used to convert biomass to carbon stock. Independent t –test was used to test for differences in C stocks of the individual C pools at significant level of 0.05. The findings of the present study revealed that the mean carbon stocks in aboveground, belowground, litter and herbs, deadwoods and soil carbon was 371.4 + 54.6, 100.3 + 14.7, 6.35 + 0.846, 9.2 + 2.02 and 136.2 + 8.42 t C ha-1 in PNF and 192.92 + 49.4, 53.09 + 13.1, 2.8 + 0.506, 10.8 + 2.15 and 90.76 + 4.97 t C ha-1 in FWC respectively, with the average aggregate carbon stocks of 623.45 + 39.5 and 350.44 + 63.5 in PNF and FWC respectively. This indicated that significantly higher C stock was recorded for PNF in all carbon pools assessed (p<0.05) except that of dead woods carbon pool which showed insignificant variation (p>0.05). The result implies that conversion of natural forest to coffee-based forest leads to a reduction of both biomass and SOC by 46.7% and 33.4% respectively and this is equivalent to the emission of about 1001 t CO2 ha-1 to the atmosphere. It was concluded that conservation programs aiming to ensure the long-term permanence of forest carbon stocks, such as REDD+, will remain limited in their success in the area unless the district effectively avoid this forest degradation. Thus, all stakeholders at the local, regional and national level should work together to implement effective conservation measures to maintain and enhance the carbon stock potential of this forest.
Keywords: Carbon loss, Coffee forest, Selective cutting, Untouched natural forest
