Consequences of wetland restoration for hydrochemistry, C, N and P balances, greenhouse gas emissions and hydrology

Drainage of peatlands over several decades reduced their natural functions as accumulators, buffers, transformers and filters for nutrients and water. Further, a new peat soil surface with fundamental differences in soil physical properties and completely different hydrology and bio-geo-chemical dynamics in the landscape occurred. Aerobic conditions in the upper horizons have resulted in oxidative peat decomposition, with concomitant emission of CO₂ to the atmosphere.

Regeneration and wise use of peatlands used for peat harvesting, agriculture and forestry is highlighted in Europe and promoted both economically and politically, for example by Kyoto Protocol (UNFCC 1998) and European Water Framework Directive (EU 2000). Many degraded peatlands have been re-wetted and there are plans to re-wet more in the near future. Re-wetting leads to saturated conditions which strongly mitigate peat decomposition, minimizes CO₂ emissions (in general) and may initiate new peat growth.

But, re-wetting of degraded peatlands is often accompanied by enhanced release of phosphorus due to changes in the redox potential of phosphorus adherent chemical elements such as iron. Thus, in managing degraded peatlands, special account must be taken of the potential for supple-mentary nutrient outputs to adjacent aquatic ecosystems.

The aim of this PhD project is to clarify effects of hydrological restoration of former peat extraction sites. Four peatlands of different trophic status and a pristine peatland will be investigated. Clarification concerns:

How does wetland restoration by re-wetting affect hydrochemistry and hydrology of the new established environment?

What do we know about mechanisms of carbon, nitrogen and phosphorus turnover and their ecosystem balances and what are the interactions between those elements in flooded conditions?

What are their concentrations in soil (peat) and water and how much will be released to the atmosphere or into adjacent ecosystems by water pathways?

What effect has re-wetting (on peatlands with different trophic status) on the emission of greenhouse gases?

Important in the work is to investigate the peat soil changes from the drained soil conditions under peat cutting situation to the new conditions after rewetting when the peat will form bottom sediments in shallow water bodies.

The project will provide new information in soil-water-atmosphere relations at 4 re-wetted landscapes in wetland vegetation re-establishment conditions. Investigations on greenhouse gas emissions (CO₂, CH₄ and N₂O) from different soil moisture conditions and soil coverage (i. e. bare soil, vegetation and open water surface) are included by using chamber techniques.

Results will provide information for the peat industry to plan after-use and to authorities as decision support in prescribing appropriate after-uses.