Woody species diversity and carbon stock potentials in homegarden agroforestry and other land use systems, northern Ethiopia

Abstract

Homegarden agroforestry (HGAF) provides wider ecosystem services in the agricultural landscapes in the tropics. However, the potentials of the homegardens for floristic species conservation and climate change mitigation were less empahsized. The present study was designed to investigate woody species diversity, carbon stock, and the relationships between woody plant species and carbon stock in the HGAF and other land use types. Three land use types were purposively selected, totalling 60 nested sample plots. The stand structure and woody plant species diversity were determined. Biomass carbon stocks were estimated employing appropriate allometric equations. Soil Organic Carbon (SOC) stocks (at 0–30 and 30–60 cm layers) were calculated. The result of the study showed a total of 38 woody plant species recorded from both HGAF and exclosures, but no report from cropland. The abundance, basal area, stem density, species richness, and Shannon and Simpson diversity indices were significantly higher in the HGAF than in exclosures. The mean SOC stock was the highest in HGs (122.13 ± 19.12 Mg ha-1). The estimated mean total ecosystem carbon stock of HGAF, cropland, and exclosure was 171.17 ± 37.25, 78.06 ± 11.97, and 92.5 ± 17.33 Mg ha-1, respectively, which was statistically significant among land use types. A positively significant correlation was observed between diversity, richness, and abundance of woody species and carbon stocks both in the HGAF and exclosure land use systems. The current study confirmed that increased woody species diversity in HGAF enhanced carbon sequestration. The HGAF land use in the northern parts of the country is scanty as compared to the southern part, where there is a rich woody species diversity. Therefore, it is recommendable to promote HGAF across agricultural landscapes of the study area, which enhances biodiversity conservation and mitigation of climate change impacts.