Impact assessment of vascular plant encroachment on water and carbon cycling in a Sphagnum dominated bog - VESBO

• Applicants: Dr. Maren Dubbert; Dr. Arndt Piayda
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428485061

Boreal and temperate bogs cover less than 3% of the earth's surface but store nearly 30% of the terrestrial carbon, accumulated over millennia by permanent soil water saturation. Natural raised bogs are characterized by a Sphagnum-moss dominated vegetation cover, but used by humans for centuries by peat extraction. The impacts of artificial drainage on ecosystem functioning and biodiversity are numerous and not limited to the tremendously increased CO2 emissions. The re-establishment of quasi-natural hydrological conditions as well as of ecosystem-typical vegetation is the main goal of ecological restoration conducted since decades. However, due to the close coupling of carbon fixation to the water balance, subtle changes in the vegetation composition can have major impacts on the ecosystem carbon sink strength.In the last decades, a change in species composition of restored bogs from Sphagnum-dominated bryophyte communities to multi-layered tree and graminoid vegetation was observed. Current investigations report contradictory effects for the impact on throughfall, evapotranspiration (ET), gross primary productivity, respiration, net CO2 balance (NEE) as well as soil carbon sink strength. A final conclusion with respect to altered ecosystem functioning in the light of climate change is missing but of increasing importance, since more and more peat mining areas are restored. The removal of trees and graminoids from bogs is a common nature conservation practice in order to reduce ET and limit further encroachment, but the effectiveness with regard to the re-establishment of near-natural hydrological conditions and their influence on the carbon balance has not been conclusively clarified.The present project proposal aims at the mechanistic analysis of ET, NEE and soil carbon sink strength of a restored, Atlantic-temperate raised bog during vascular plant encroachment. Focus will be placed on the partitioning of total ecosystem ET and NEE fluxes by Eddy Covariance and chamber measurements in situ into bryophyte, graminoid and tree contributions. Results are used to parameterize a modern soil-vegetation-atmosphere-transport model able to simulate bryophyte and vascular plant layers on peat soil. The model, jointly with the empirical data, is used to quantify seasonal changes in plant functional group flux contributions depending on altered environmental conditions. The holistic process understanding is of high relevance for the NEE estimation of restored bog ecosystems under changing climatic conditions and vegetation compositions and thus, their impact on climate change. The improved knowledge about different interactions of plant functional groups with mass and energy fluxes of the bog ecosystem will be directly valorised by the assessment of restoration activities as well as nature conservation and emission mitigation measures throughout Europe.

• DFG Programme: Research Grants
• International Connection: Finland
• Major Instrumentation: Gasanlysegerät
• Instrumentation Group: 1520 Meßgeräte für Gase (O2, CO2)
• Co-Investigators: Dr. Bärbel Tiemeyer; Professorin Dr. Christiane Werner
• Cooperation Partner: Dr. Samuli Launiainen