Woody Species Diversity and Aboveground Live Carbon Storage in the Agroforestry Systems of Tarcha Zuria District, Dawuro Zone, Southwest Ethiopia

Abstract

Agroforestry systems, which integrate trees with crops and/or livestock, play a crucial role in enhancing biodiversity, promoting sustainability, and sequestering carbon to combat climate change. Understanding the ecological and carbon storage potential of these systems can support sustainable land management and climate change mitigation strategies. This study investigated woody species diversity and aboveground live carbon storage within agroforestry systems of Tarcha Zuria district, Dawuro Zone, Southwest Ethiopia. Agroforestry systems were stratified into three land use types: homegarden, cropland, and pastureland. Four transects, each 14 km long and 1 km wide on either side, were laid across the different land-use types at regular intervals. A total of 42 sample plots were established along transicts sysematically with 14 plots in each land use type. Vegetation parameters, including diameter at breast height (DBH), height, and species type were recorded. The data analysis used structural (height, DBH, and basal area) and compositional (frequency, diversity, and density) parameters. Data were analyzed using past software with descriptive statistics for the Shannon-Wiener diversity index and Sorenson’s similarity index. Aboveground live biomass (AGB) of woody species with DBH ≥ 5 cm was calculated using the updated nondestructive allometric equation: AGB = 0.0673(ρD2H) 0.976. Aboveground carbon (AGC) was estimated as 50% of AGB. One-way analysis of variance (ANOVA) was used to test the differences in AGC across land use types, followed by Tukey’s HSD test for mean comparisons. A total of 62 woody species belonging to 28 families and 46 genera were recorded and documented across 42 sample plots. Similarities in species composition were higher between home garden and cropland (77%) and lowest between cropland and pastureland (49%). Woody species diversity and carbon storage varied significantly among the land use types. Woody species diversity, species richness, and species density were significantly higher in pastureland, while species evenness was greater in cropland compared to the other land use types. The AGC stored in homegarden (19.15 t/ha) was significantly higher than both in cropland (7.87 t/ha) and pastureland (6.35 t/ha). The variation in carbon storage among different land use types was statistically significant (F = 77.728, P = 0). Finally, the study demonstrated that woody species in the various agroforestry systems play a key role in carbon sequestration. Their conservation is therefore recommended to sustain this benefit.