Impacts of forest harvesting on nutrient, sediment and dissolved organic carbon exports from drained peatlands: A literature review, synthesis and suggestions for the future

- The literature related to forest harvesting on drained peatlands was reviewed.
- Focus on identifying the best practices for mitigation of water quality deterioration.
- So far no practices to effectively mitigate all harmful consequences concurrently.
- So far no practices to mitigate DOC and dissolved organic nutrient exports.
- Future studies should focus on assessing the impacts of partial harvestings.

We reviewed the studies on the impacts of forest harvesting on nutrient, sediment, and dissolved organic carbon (DOC) exports from drained peatlands with the aim to identify the best practices for mitigation of detrimental water quality impacts. We concluded that so far there are no such practices that would effectively mitigate all harmful consequences of forest harvestings concurrently. Controlling water levels by executing drainage operations immediately after harvesting may decrease the exports of easily soluble and redox-sensitive elements, but the very intensive drainage necessary to lower water levels in highly decomposed peats, as those that typify peats at the clear-felling phase, would result in large exports of sediments and mineral nitrogen. Establishing a wetland buffer area between a forest harvested peatland and the receiving water course may decrease sediment and inorganic nutrient exports, but restored wetland buffers, in particular, may act as a source of DOC and dissolved organic nutrients to receiving water courses. Whole-tree harvesting might decrease nutrient exports in blanket peat areas, but its practical application is hindered by nutritional and forest harvest technology related aspects. We propose that future studies should focus on assessing the impacts of partial harvestings, which so far have received very limited attention.