Role of Indigenous Dryland Agroforestry System for Biodiversity Conservation and Carbon Storage in Tigray, Northern Ethiopia

Abstract Background Agroforestry (AF) is an age-old practice in the farming system of Ethiopian dry lands. So far, several studies conducted in the field of AF focused on system design, soil fertility management and system interactions. Less emphasis has been given to the biodiversity and climate change mitigation aspects. The objective of this paper was to evaluate the woody species diversity, biomass carbon (C) and soil organic carbon (SOC) stock of the dry land indigenous AF practices. A total of 197 smallholder farmers representing four AF practices were systematically selected from lowland, midland and highland. Woody species inventory was done on the randomly established plot of each farm. Results A total of 59 species, belonging to 48 genera and 32 families were recorded. Shannon diversity index (H’) of highland agroecology was higher in-home garden AF while in the midland and lowland the higher H’ was recorded in parkland AF. Smallholding ecosystem C stocks (sum of total biomass C and SOC 0 –60 cm) ranged from 77 to 135 Mg ha −1 .The mean total biomass C stock of woodlot AF practice (31 Mg C ha -1 ) was significantly higher than the other three AF practices. SOC stocks (0–60 cm) were greater in boundary planting (113 Mg C ha -1 ) followed by the home garden (109 Mg C ha -1 ) and woodlot (97 Mg C ha -1 ) AF practices. Conclusions The higher species richness was recorded on the home garden and parkland small household agroforestry system as compared to woodlot agroforestry systems. Likewise, the higher Shannon diversity and evenness were found on the home garden agroforestry system.. As compared to other AF systems, our study revealed that rotational woodlot and boundary planting AF practice accounts higher biomass and SOC stock, respectively. We found that biodiversity is synergy with SOC stock but can be seen as an independent agro-ecosystem function that may not directly correlated to biomass and total agroforestry carbon storage. Finally, our work concluded that home garden and boundary agroforestry can strategically promote to maximize biodiversity and carbon storage of the dry land ecosystem.