Conversion of natural forests to farmlands and its associated woody species diversity and carbon stocks in a span of 33 years (1984 to 2016): in the case of southwestern Ethiopia

Abstract

Background Gura-Ferda forest is one of the Afromontane rainforests in the southwestern region of Ethiopia. However, since 1984, large parts of this forest have become increasingly disturbed and fragmented due to forest conversion into forest farm interface and farmlands. The study was conducted to assess changes of woody species diversity and carbon stock in association with the conversion of natural forest to forest farm interface and farmlands. Methods Data were collected from natural forest, forest farm interface and farmland which are historically forest lands before 1984. A total of 90 nested plots (20m×20m for natural forest and forest farm interface; 50m*100m for farmland)) were established for inventory of woody species. Three 1m×1m subplots were established to collect litter and soil samples. A total of 180 soil samples were collected. The total carbon stocks were estimated by summing carbon stock in the biomass and soil (0-60 cm depth). Results Results showed that Shannon-Wiener diversity (H’) in forest farm interface (H’ = 1.42±0.49) is significantly lower than that of natural forest (H’ = 2.72±0.31) but significantly higher than farmland (H’ = 1.08±0.57). The total carbon stocks of natural forest (388.54±161.63 Mg C ha-1) were approximately 1.53 and 2.67 times higher than that of forest farm interface (252.95±41.86 Mg C ha-1) and farmland (145.58±25.94 Mg C ha-1). Conclusion Our study revealed that along the conversion gradient of natural forest to forest farm interface and farmland there was a significant change of woody species diversity and carbon stocks.