EFFECT OF VEGETATION TYPES AND ELEVATION ON CARBON STOCK POTENTIAL OF WOODY SPECIES OF JORGO-WATO NATURAL FOREST, WESTERN ETHIOPIA

Abstract

Forests play significant role in climate change mitigation through capturing atmospheric carbon. Ethiopia, despite being one of the biodiverse countries at the global, it has limited forest resources distributed in certain parts of its territory. The moist evergreen Afromontane forests of Western Ethiopia are among the Ethiopian forests that contribute significantly to the climate change mitigation. Jorgo Wato Forest is one of the moist Afromontane forests in Western Ethiopia that may contribute in climate change mitigation. However, no study on the carbon storage potential of the forest has been conducted yet. Thus, this study was conducted to assess woody species composition and compare carbon stock potential in different vegetation types and altitudinal gradients. A forest was stratified into three vegetation categories including Tree grass land (TGL), High forest (HF) and Dense wood land (DWL). The altitudinal gradients in each vegetation type were classified in to three ranges from the bottom to the top of the forest. A three parallel transect lines were laid down vertically in each vegetation type along altitudinal gradients. In each vegetation type, total 36 nested quadrats having 20m x 20 m and 1m x 1m sub- plots were laid down following altitudinal gradients along the transect lines to assess tree parameters, soil samples, seedlings and litters falls. Total 108 composite soil samples were collected from two depths (0-15cm and 15-30cm) to determine soil organic carbon (SOC). A total of 39 woody species that belong to 35 genera and 30 families were identified in the forest. The overall mean stem density/ha, species richness/plot, Shannon-Wiener Diversity Index (H’) and evenness (J) were 1087.5 plants/ha, 8.09, 1.715 and 0.81, respectively. The species richness, Shannon-Wiener Diversity Index and evenness significantly varied (p<0.05) along elevation gradient but did not show significant different (p>0.05) among vegetation type. The mean total carbon stock density of Jorgo Wato forest was 447.67 t/ha with equivalent to emission of 1642.95 of CO2 t/ha. The mean carbon pools of the forest were 236.213 t/ha, 63.68 t/ha, 13.979 t/ha, 1.34 t/ha and 132.45t/ha in aboveground carbon (AGC), below ground carbon (BGC), dead wood carbon (DWC), Litter carbon (LC) and soil organic carbon (SOC) respectively. Some carbon pools showed significant differences (p<0.05) between vegetation types and elevation ranges, while others showed no difference. The mean total carbon densities in Tree Grassland (TGL), High Forest (HF) and Dense Wood Land (DWL) were 405.049±97.98t/ha,544.663±208.06t/ha and 393.308±147.125t/ha respectively. The study results revealed that the forest had a potential of carbon storage, contributing to climate change mitigation. The total carbon storage densities were found to be significantly different among vegetation types and altitude ranges. Therefore, the best way and design to protect forest regarding natural vegetation categories needs to be applied to enhance and expand the benefits of ecosystem services, mainly the potential of carbon storage in climate change mitigation