In agroforestry practice in Hawassa Zuria district
In Ethiopia the majority of the people depend on limited farmlands which is leading to replacement of the forest and other mountainous land by agricultural land to feed the rising population. This can be related with climate change and loss of biodiversity. Separately use of limited land for food crop, tree planting and other purpose was not achievable for land users. Agroforestry practices promotes planting of crops and trees on the same piece of land (Kremen et al., 2012) and helps to sink CO2 and increase biodiversity.
The Tree-enset dominated homegarden agroforestry practice in Hawassa Zuria district dominated by native perennial crops such as Enset (Enset ventricosum Welw. Cheesman), trees (Cordia africana and Persia American) and co-dominated with coffee and other annual crops. Enset is a perennial herbaceous crop and a staple food for about 15 million people in the southern Ethiopia (Abebe et al., 2013). Cordia africana and Persia American are perennial trees that are used for commercial purpose. Homegardens in most of Southern Ethiopia are extended farm systems from where households derive all their subsistence and cash needs. The average size of these agroforestry homegardens is about 0.7 ha, and they support a very dense population of 500–1000 people km-2 (Abebe et al., 2010).
Homegarden agroforestry practice plays an important role in mitigating climate change by sinking CO2 and diversifies woody species around homestead (Duguma, 2010). However, C storage in agroforestry practices can be affected by altitude which affects the patterns of tree species distribution (McEwan et al., 2011). Altitude has a significant effect on climatic factors such as temperature and precipitation. It strongly affects species composition, biomass, stem size, stand density, consequently affects the quantity and turnover of organic matter (Sheikh et al., 2009). A study was carried out on soil physicochemical properties and grain yield of Maize in the parkland agroforestry practice of the study area (Manjur et al., 2014), and on biomass and soil C stock of indigenous agroforestry systems in coffee-tree based and enset-coffee based in the south-eastern Rift Valley escarpment in gedeo zone (Negash and Starr, 2015). Limited study was carried out on tree-enset dominated homegarden agroforestry by considering altitude that could affect C stock and woody species diversity. Thus, this work was done to evaluate and correlate the altitude with woody species C stock and diversity. Hence, such research on C stock and woody specie diversity in tree-enset dominated homegarden agroforestry is needed to develop sustainable management planning that help to enhance the environmental and economic services through upgrading plant species diversity and carbon financing in homegarden agroforestry practice. Due to poor awareness, farmer cut trees for fuel food and other purposes. However, agroforestry intensification in the form of reduction in shade tree leads to reducing tree diversity and C storage capacity of agroforestry (Tscharntke et al., 2011; Tadesse et al., 2014). This also increases the emission of CO2 to the atmosphere and decreases the tree species diversity. Therefore, this study was done to estimate the C stock and woody species diversity in tree-enset dominated homegarden agroforestry practice along an altitudinal gradient.