WOODY SPECIES DIVERSITY AND CARBON STOCK POTENTIAL OF AGRI-SILVICULTURE OF FEDIS DISTRICT, EASTERN ETHIOPIA

Abstract

Previous vegetation studies and their ecosystem services have concentrated largely on natural ecosystems, with less emphasis on managed areas like agricultural systems. Moreover, the protection and conservation of vegetation would be not only successful in protected areas alone but also in the agriculture environment and surrounding it. More recently, human-altered ecosystems such as conventional agroforestry like agri-silviculture have become increasingly conscious of their ability to sustain woody species and ecological services like; mitigation of climate change. Thus, this study was conducted to assess woody species diversity and carbon stock potential of agri-silvicultural systems of Fedis District, Eastern Ethiopia. Fedis District was selected purposively since the agri-silvicultural system is widely practiced. Then two agri-silviculture systems practicing kebeles were identified. Each selected potential kebele was stratified into three villages. Furthermore, ten rectangular quadrats 100 m X 50 m or 0.5 ha were established at 100 m intervals between two quadrats Hence, a total of sixty quadrats were used for vegetation data and soil sample collection. DBH and height of each woody species found within each quadrat were recorded by the use of a caliper and hypsometer respectively. Woody species diversity analysis was carried out by the Shannon Weiner Diversity index by the use of the R software program. For soil sampling, 1 m X 1 m was laid out, four at the corner and one at the centre of each main quadrat. At each sampling point of 1 m X 1 m, a soil sample was collected at the depth of 0-30cm and thoroughly mixed in a plastic bag to produce a 1 kg composite sample. To determine soil bulk density, an undisturbed sample was collected from the centre of the central sub-quadrat of the main quadrat using a core-sampler auger. Therefore, a total of 60 composite and 60 undisturbed samples were collected. A total of 27 woody species representing 26 genera and 20 families were collected from the study site. Shannon Weiner diversity index and evenness have resulted in 2.12 and 0.64 respectively. With population structure, Cordia africana and Faidherbia albida together constitute about 54% of the total plant species in the study. Faidherbia albida was the most frequent encountered woody species following Cordia africana. The total basal area for the study area was about 66.77 m2 for woody species having DBH ≥ 2.5 cm with a 300 value of IVI. The mean total carbon stock of the study area was 63.9 Mg C ha-1, of which 8.6 Mg C ha-1, 2.3 Mg C ha-1and 53 Mg C ha-1 were contained above ground, below ground, and soil organic carbon, respectively. The results of the study showed that the agri-silviculture agroforestry practice has a large potential to deliver regulating ecosystem services like opportunities to mitigate the impending climate-changing through carbon sequestration and increasing the resilience of the agricultural system at Fedis District. Therefore, we recommend the inclusion of agri-silviculture in the Nationally Determined Contribution of Ethiopia.