Water level management of wetlands in ...

Wetlands are integral components of our natural environment since they provide many critical ecosystem services to humanity, such as water purification, climate change mitigation, flood control, and biodiversity. Although wetlands can convey resilience to some degree of changes, they might be vulnerable to climate change. Altered hydrology and rising temperatures can turn the wetland services into disservices. This thesis investigates the impact of different climate scenarios, both current and future climate scenarios, on wetland ecosystems, natural (peatland), and constructed wetlands. Since 2017, a mesocosm experiment has been conducted within four climate chambers to simulate current (2017-2020 in the experiment and 2016-2019 in real-time) and future climate scenarios based on representative concentration pathways scenarios (RCP 2.6, RCP 4.5, RCP 8.5) for peatlands and constructed wetland. The main aim of the thesis was to investigate the impact of climate change scenarios and water level management on 1) water quality (physiochemical changes in peatland and constructed wetland outflow) and 2) carbon dioxide emissions from peatland. The results of the experiment revealed that the short-term (one year) impact of climate change simulation on the water purification function of both constructed wetland and peatland (ombrotrophic bog) is insignificant when the hydrology of the systems is not a stress factor (no occurrence of flood or drought). However, the response of the water purification function of two different wetlands, constructed wetland and peatland, showed a contrasting tendency along with the increasing temperature trend of climate scenarios. This suggests that while the water quality of constructed wetland may improve with future warmer climate scenarios (no water stress), the water quality of peatland may gradually deteriorate. The findings of a longer-term (three-year) simulation of climate change and water level control on peatland water quality demonstrated that climate change had still no significant effect on peatland water quality, however, the water level control had a substantial impact. Water level management during the drought and post-drought period could improve the water quality of managed mesocosms by 2-50 times compared to the unmanaged system. The investigation of climate change and water level management impact on CO2 sink function of peatland suggested that climate change alone might not have a significant impact. However, the influence of water level management, both alone and in interaction with climate change, can have a significant impact on the CO2 sink function of peatland. The most favorable influence of water level management on CO2 sink function was found in peatland mesocosms under warmer climate scenarios (RCP 4.5 and RCP 8.5) due to the enhanced growth of vascular plants, but this was not the case for the systems under the colder climate scenarios, current and RCP 2.6 climate scenario. In brief, water level management during drought is necessary for warmer climate scenarios such as RCP 4.5 and RCP 8.5 to prevent the system from shifting from CO2 sink to source, while it is unnecessary for the current climate and RCP 2.6.