| Most rivers are highly degraded ecosystems, and eutrophication has been the major cause for low water quality and loss in biodiversity. Therefore, many streams and rivers are being restored through the establishment of wetlands, which retain nutrients and foster biodiversity. Wetland establishment entails the expansion of aquatic and semi-aquatic plants (hereafter referred as to macrophytes), which provide key ecosystem services but also can act as strong sources of methane, a powerful greenhouse gas. At the same time, macrophyte stands are often highly productive, and sequester carbon in belowground biomass and soil, which has a cooling effect on climate. The balance between methane emission and carbon sequestration of macrophytes, and therefore the effect of their expansion on climate, is insufficiently understood because it results from the complex interplay of environmental conditions, plant traits and microbial processes.
The purpose of the proposed doctoral research project is to create new knowledge that enables practitioners to design riverine wetland restoration projects (i.e. establishment of wetlands along the flowpath of surface water, including the smallest streams and ditches) that maximize the intended benefits for biodiversity and water quality at minimal climate footprint. Realizing that this purpose can be achieved through plantation of climate-beneficial macrophyte communities, we aim at:
1) establishing novel Climate Functional Types (CFTs) of macrophytes in relation to ecological and physiological species traits,
2) quantifying the effect of macrophyte diversity on climate by evaluating the climate footprint of diverse assemblages of macrophyte species and CFTs, and
3) measuring the overall climate footprint of restoration projects using new airborne methane flux technology, and including belowground organic carbon sequestration.
The proposed research will therefore be conducted in close collaboration with key stakeholders in water conservation and river restoration, to create new scientific knowledge that helps practitioners to restore riverine wetlands with co-benefits for climate. Research will be conducted in controlled greenhouse experiments, but also in the field on current restoration projects, warranting that mechanistic understanding is linked to real-world carbon and methane fluxes, and that the research is responsive to the realities and needs of stakeholders. Various dissemination activities targeted at the wider water conservation community will ensure that the new scientific evidence reaches practitioners without delay.
The work will be conducted within a team of experienced scientists of mixed career age and gender, with complementary competencies in aquatic carbon cycling, macrophyte ecology, community ecology, river restoration and gas exchange measurement. The education of a PhD student in this research area will build important capacity for improved multifunctionality in river restoration projects in Sweden and elsewhere. By addressing how degraded Swedish rivers can be restored in a way that benefits biodiversity and mitigates eutrophication as well as climate change, this research is at the core of the Lamm Foundation’s purpose to support research in the conservation of Swedish waters.
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