Forest Structure, Carbon Stocks and Leaf Litter Decomposition of two Selected Afromontane Forests in the Western Escarpment of Central Rift Valley and the Gibe Watershed, Ethiopia
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Date
2017-06
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Addis Ababa Universty
Abstract
The Afromontane forests of Ethiopia have been under a serious degradation threat.
Understanding forest structure, floristic compositions and their important roles in
providing ecosystem functions like climate change mitigation through carbon
sequestration and nutrient flow dynamics are important in targeting sustainable forest
management strategies. Therefore, the major objectives of this study were to determine; i/
forest structure, plant community composition in relation to environmental factors and
carbon stocks of Biteyu forest and ii/ quantifying forest structure, carbon stocks, litterfall
and leaf litter decomposition dynamics, and nutrient release patterns from the Boter-
Becho forest. Systematic sampling technique was employed for vegetation and
environmental data collection. Thirty plots of 900 m2 and 71 plots of the same quadrat
size were selected from the Biteyu and Boter-Becho forests, respectively. Total carbon
stocks (t ha-1) were estimated from aboveground biomass, belowground bimass, soil and
forest litter carbon pools. The appropriate allometric models were applied for
aboveground and belowground biomass estimations. To determine litterfall dynamics in
Boter-Becho forest, two sites of the forest namely, low disturbed (LD) and high disturbed
(HD) were selected subjectively using field observations. A total of 20 litter traps, ten for
each site were deployed. Two hundred forty collections were made from 4th March 2014
to 3rd February 2015, and monthly collections were oven dried at 80 0C for 24 hrs to
constant weight. Similarly, the decomposition rate of leaf litter in Boter-Becho forest was
investigated using the first order negative exponential decay equation. Different data
analyses techniques were employed using R statistical software. The findings showed 190
plant species distributed among 154 genera and 73 families in Biteyu forest. Moreover,
altitude and slope strongly affect the community structure of Biteyu forest. The estimates
of total carbon stock in Biteyu and Boter-Becho forests was 166 ± 16.4 and 393 ± 24 t ha-
,1 respectively. On the other hand, the amount of total litterfall estimated in Boter-Becho
forest was 8.7 t ha- l yr-1. At the end of one year, 66.02% and 66.72% of the leaf litter was
decomposed in LD and HD sites, respectively. Consequently, the annual decomposition
rate constant measured for Boter-Becho forest was 1.405 year-1(the average of the two
sites). With regard to carbon and nutrient release in the Boter-Becho forest, there was no significant difference (P > 0.05) in their mean concentration remaining except K between
two sites. Similarly, no strong relationships were observed between initial leaf litter
chemistry and C, N, P concentration (P > 0.05) released during the decomposition in
both sites. There was high anthropogenic effect and high dependence of the local
community in Biteyu forest so that forest conservation and restoration measures should
be sought. Moreover, the variation in rainfall and temperature are responsible for
controlling litterfall production, rate of litter decomposition, C and nutrient release
pattern in the Boter-Becho forest. Therefore, the interventions, which reduce the climate
change effect, would be very important in the maintenance of forest ecosystem
functioning.
Key-words/phrases: Biteyu-forest, Boter-Becho forest, Carbon stocks, forest
disturbance, leaf litter decomposition, Litterfall, Nutrient Release
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Keywords
Biteyu-forest, Boter-Becho forest, Carbon stocks, Forest disturbance, leaf litter decomposition, Litterfall, Nutrient Release