The effects of long‐term drainage and short‐term restoration on dissolved organic C concentrations and optical properties in the Baijianghe Peatland

Peatlands are important reservoirs of terrestrial carbon (C), whose fate can have implications for the global C cycle and climate change. Many peatlands around the world have been drained for agriculture and forestry and restored later on hoping to reduce C emissions and improve water quality. However, the actual effects of these management practices remain unclear. To address this, we investigated the concentration and quality of dissolved organic C (DOC) and water chemistry (nutrient and Fe concentrations) in the surface water (creeks and ditches) of the natural, drained, and restored areas along an elevation gradient of the Baijianghe (BJH) peatland in northeast China from 2017 to 2020. We found significantly higher DOC concentrations in the natural than the drained area, with a heavier, more fulvic, and less aromatic DOC composition upslope, but the difference in DOC quality became smaller downslope. Restoration, on the other hand, did not bring DOC concentrations or quality back to the natural conditions within 2 years. These variations in DOC concentration and quality were closely associated with dissolved Fe concentration, highlighting the role of the Fe redox cycle, as Fe(II) can catalyse phenol oxidation activities and promote DOC production. Vegetation also affected DOC characteristics, as the drained and restored areas were dominated by shrubs with woodier tissues, which probably released less in amount but more recalcitrant DOC. Our study features rare side‐by‐side comparisons between pristine, drained, and restored areas of the same peatland, and sheds light on factors affecting peatland DOC under different management practices.