| Abstract |
Changes in vegetation or land use that affects soil respiration are a major concern for global climate change. Bush clearing in north-central Namibia has been used as a solution to problems of bush encroachment. However, the effect of bush clearing on soil processes, such as the carbon cycle and soil CO2 efflux has not yet been quantified in Namibia. The main aim of this study was to determine and compare the amount of soil respiration between the cleared and uncleared sites at different seasons and also to determine the effect of soil temperature and moisture on soil respiration in two farms; Erichsfelde and CCF located in Otjozondjupa region. Soil respiration was measured using a soil respiration chamber connected to the Infrared Gas Analyzer LI-COR 6400 XT. The results showed no significant difference in soil respiration between the cleared and uncleared sites at CCF in both seasons (P>0.05). This could be due to an equal amount of soil respiration between root respiration (as a result of high root biomass of woody vegetation) in the uncleared site and microbial respiration from increased litter decomposition together with root respiration of grass and herbaceous plants in the cleared site. On the other hand, both seasons at Erichsfelde showed that soil respiration was significantly higher in the uncleared site than in the cleared site (P<0.05). This could be attributed to the higher root biomass and litter content in the uncleared site than in the cleared site. Both study areas showed significantly higher soil respiration in the wet season than in the dry season (P<0.05) due to high root activities, high decomposition rate of litter and substrate availability because the soil is wet and vegetation productivity is high and active. Apart from the dry season of Erichsfelde that showed a very weak negative correlation, the rest showed no significant correlation between soil respiration and soil temperature. At the same time, soil respiration exhibited a positive correlation with soil moisture. Despite the negative effect of bush clearing on atmospheric CO₂ absorption, this study concluded that bush clearing itself does not lead to increased soil CO₂ efflux. However, there is a need for ongoing and extended studies on soil CO₂ efflux in different parts of the country and long term soil respiration monitoring, with special emphasis on the times directly after the land. |
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