Influence of micro-environmental conditions on ecosystem exchanges in the afro-alpine zone of mount Kilimanjaro, Tanzania
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Date
2013
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Publisher
Sokoine University of Agriculture
Abstract
This study was carried out in the alpine ecosystem of Mount Kilimanjaro (co, 4000 m
a.s.l), from July 2012 to August 2012 with the aim of assessing the influence of micro
environmental conditions on ecosystem exchanges of CO2. A total of 18 plastic soil
frames with either single or combination of dominant species were used to determine and
estimate the net ecosystem exchange of CO2 (FNEE) and ecosystem respiration (Reco),
biomass and leaf area of dominant species, and to establish temporal and spatial variation
on ecosystem CO2 exchanges. To achieve that, manually operated closed gas exchange
chambers referred to as light chamber to measure net ecosystem exchange of CO2 (FNEE)
and dark chamber to measure ecosystem respiration (Reco) were used. Later, the above
ground plant biomass in each soil frame was harvested for leaf area and biomass
determination. Leaf area and biomasses were obtained using digital scanner and through
oven drying at 80 °C for 48 hours respectively. In order to assess temporal and spatial
variations, soil frames were located in three subplots for repetition and measurement
rounds were carried out from morning (0800 hours) to evening (17.00 hours). Both
correlation and regression analysis were used to assess diurnal dependencies of CO2
concentrations on the environmental variables. The CO2 fluxes were correlated to
Photosynthetic Active Radiation (PAR) at (R2>0.95). The mean daily FNEE ranged from
1.3398 pmol m'2 s'1 to -6.2150 pmol m'2 s'1 and Reco from 1.3474 pmol m'2 s'1 to 4.6695
pmol m'2 s'1 while green biomass ranged from 302.2 gm'2 to 48.81 gm'2. The highest CO2
fluxes were evident in combination of species. Subsequently, PAR, air and soil
temperatures explain most temporal variability of CO2 fluxes. Nonetheless, micro-
environmental conditions created by vegetation structures that increased the leaf area for
canopy level light utilization and green biomass seemed also to play important roles on
CO2 exchanges.
Description
Dissertation
Keywords
Alpine ecosystem, Kilimanjaro afro-alpine, Tropical alpine ecosystem