Assessing Wetland Health Through Decomposition in Degraded and Semi-Intact Wetlands in Uganda

Abstract

The assessment of ecological functions of wetland areas offers a more dependable measure of the health of these ecosystems. The study examined the decomposition process within two urban wetlands with different degree of disturbance as a means of evaluating their ecological health and functionality. The study also inspected the influence of various physicochemical parameters on rates of decomposition. 20g of Pennisetum purpureum, an increasingly common invasive species in natural ecosystems due to human activities, was harvested, air dried to a constant weight and utilised in litter bag decomposition experiments within the two wetlands. Invasive species such as Pennisetum purpureum often have similar impacts across different ecosystems, making them useful models for generalizing results. Changes in leaf mass over time and leaf breakdown rates using a single exponential decay model were determined. Wetland physicochemical characteristics (pH, temperature, TDS, dissolved oxygen & conductivity) were also measured and recorded for the two wetlands within the duration of the experiment. Pearson’s correlation test was conducted to validate the relationship between the physico-chemical parameters and decomposition rates of the two different wetlands. Results revealed a significant difference in mean decomposition rates, (p < 0.001) with the degraded wetland exhibiting a higher value (0.20 kd-1) compared to the semi-intact wetland (0.015 kd-1). The rates of decomposition were also found to positively correlate with temperature (r = 0.54), conductivity and pH, while showing a slight negative correlation with TDS and dissolved oxygen. The study concluded that rapid decomposition in degraded wetlands is primarily due to human disturbances that alter their physical characteristics indicating deteriorating ecological health inform of eutrophication, altered native plant growth, subsidence, decreased carbon storage, oxygen depletion and so forth. Additionally, the alternating periods of inundation within the wetlands, caused by the wet-dry cycles is a primary influencer of decomposition rates in wetlands especially within the tropical region