Tree species diversity and its relationship with carbon stock in the parkland agroforestry of Northern Ethiopia

Abstract Parkland agroforestry can store carbon and conserves biodiversity. Studying the relationship between carbon stock and biodiversity is crucial in understanding the tradeoff between major benefits of the parkland agroforestry system, and way to achieve the optimum balance between them. Therefore, this study aims to estimate the biomass and SOC in community type, and explore the relationship between carbon stocks and diversity. Tree with DBH (Diameter at breast height) > 2 cm was measured and species were identified in 75 (50x100m) randomly located plots. Species richness (S), Species evenness (J), Shannon-weiner diversity index (H’) and Simpson diversity index (D) of the study area were 3.02, 0.81, 0.82 and 0.46 respectively. Similarly, the mean aboveground (AGC), belowground (BGC) and soil organic (SOC) carbon were 7.9, 3.03 and 20.07 Mg C ha-1 respectively. There was a liner and weakly significant correlation between AGC and tree J in plant community 2 (r = −0.558, P < 0.05) and 3 (r = −0.451, P < 0.05), and there was a negative correlation between J (r = −0.552, P < 0.05), D (r = −0.646, P < 0.05) and H’ (r = −0.643, P < 0.05) with TC (Total carbon) in plant community 2. However, there was no significant relationship between J, D and H’ with TC in plant communities 1 and 3. In these parkland agroforestry systems, the relationship tree species diversity with AGC and TC appeared to be highly variable; it indicates that parkland agroforestry systems have significantly improved the vegetation and SOC. However, forest carbon enhancement cannot assure the biodiversity conservation and promotion in a parkland agroforestry system.