Peatland ditching and subsequent afforestation as a driver of surface water browning - the role of fungal communities

Browning - that freshwaters are becoming increasingly brown - is widely observed in northern regions, and is caused by increased leaking of dissolved organic carbon (DOC) and iron (Fe) from the catchment.

This phenomenon has received ample attention, both by the scientific and the water management community, as it has important consequences for ecosystem functions and services provided by freshwaters. Recent research demonstrates the important role of coniferous afforestation as an underlying driver of browning.

This is due to the buildup of organic soil layers under coniferous forests, which sustain high DOC and Fe export, but it may also be linked to the parallel practice of ditching peat soils to promote forestry.

The aims of the proposed project are therefore to 1) Determine the importance of peatland ditching, and subsequent afforestation, as a driver of browning, 2) Unravel the role of ectomycorrhizal fungi - which become more active in peatland soils after ditching - for the mobilization of DOC and Fe.

The project makes use of historical information on land-cover change (aerial photographs) in individual catchments and water color in corresponding lakes, field measurements in peatland gradients with different influence of ditching, and controlled experiments.

It will make a significant contribution by elucidating where in the landscape browning originates, which is critical for our understanding on how and where local measures can be implemented to mitigate browning.