Environmental and economic performance of forestry on drained peatlands was reviewed to consider whether continuous cover forestry (CCF) could be a feasible alternative to even-aged management (EM). CCF was regarded feasible particularly because continuously maintaining a tree stand with significant transpiration and interception capacity would decrease the need for ditch network maintenance. Managing CCF forests in such a way that the ground water levels are lower than in clear-cut EM forests but higher than in mature EM forests could decrease greenhouse gas emissions and negative water quality impacts caused both by anoxic redox reactions and oxidation and mineralization of deep peat layers. Regeneration studies indicated potential for satisfactory natural regeneration under CCF on drained peatlands. An economic advantage in CCF over EM is that fewer investments are needed to establish the forest stand and sustain its growth. Thus, even if the growth of trees in CCF forests were lower than in EM forests, CCF could at least 2 in some peatland sites turn out to be a more profitable forest management regime. An advantage of CCF from the viewpoint of socially optimal forest management is that it plausibly reduces the negative externalities of management compared to EM. We propose that future research in drained peatland forests should focus on assessing the economic and environmental feasibility of CCF.

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Peatland drainage has been an important component of forestry management in the boreal zone and the resulting ditch networks are maintained regularly to sustain forest productivity. In Finland, this is recognized as the most detrimental forestry practice increasing diffuse loads of suspended solids. Alongside forestry management on peatlands, interest in peatland restoration has grown lately. Distributed hydrological modeling has the potential to address these matters by recognizing relevant physical mechanisms and identifying most suitable strategies for mitigating undesired outcomes. This study investigates the utility of such a modeling approach in a drained peatland forest environment. To provide a suitable tool for this purpose, we coupled channel network flow to the three-dimensional distributed hydrological model FLUSH. The resulting model was applied to a 5.2 ha drained peatland forest catchment in Eastern Finland. The model was calibrated and validated using field measurements obtained over frost-free periods of five months. The application showed that distributed modeling can disentangle the importance of spatial factors on local soil moisture conditions, which is significant as peatland drainage aims to control these conditions. In our application, we limited the spatial aspect to the topography and the drainage network, and found that the drainage configuration had a clear effect on the spatial soil moisture patterns but that the effect was less pronounced during the wetter summer. Future applications of distributed modeling in this field comprises investigating the impacts of other spatial factors, modeling channel erosion and solid transport to address strategies for their mitigation, and evaluating restoration schemes.

Drainage is an essential prerequisite in peatland forest management, which generally, but not always, increases stand growth. Growth response depends on weather conditions, stand and site characteristics, management and biogeochemical processes. We constructed a SUSI-simulator (SUoSImulaattori, in Finnish), which describes hydrology, stand growth and nutrient availability under different management, site types and weather conditions. In the model development and sensitivity analysis, we used water table (WT) and stand growth data from 11 Scots pine stands. The simulator was validated against a larger dataset collected from boreal drained peatlands in Finland. In validation, SUSI was shown to predict WT and stand growth well. Stand growth was mainly limited by inadequate potassium supply, and in Sphagnum peats by low oxygen availability. Model application was demonstrated for ditch network maintenance (DNM) by comparing stand growth with shallow (−0.3 m) and deep ditches (−0.9 m): The growth responses varied between 0.5 and 3.5 m3 ha−1 in five years, which is comparable to experimental results. SUSI can promote sustainable peatland management and help in avoiding unnecessary drainage operations and associated environmental effects, such as increased carbon emissions, peat subsidence, and nutrient leaching. The source code is publicly available, and the modular structure allows model extension to cost–benefit analyses and nutrient export to water courses.

We developed and applied a computational model for simulating unsteady flow in a drainage network of a boreal forested peatland site. The input to the model was the hourly runoff produced by a hydrological model. The simulations of the flow in the ditch network were performed using an iterative procedure for solving the Saint-Venant equations that govern the flow in each of the network channels. These equations were solved separately for each ditch branch, and the flow depths at the junctions were corrected using the method of characteristics. The model was applied to the drainage network of a peatland catchment in Eastern Finland over a period of 15 months. Because flow resistance in the ditches depended strongly on flow conditions, flow resistance (Manning's n) was introduced as a function of discharge. The model was calibrated and validated against field data and the simulation results were further applied to assess erosion risk. The highest risk of erosion occurred during long lasting flows induced by snowmelt at ditch sections with a steep slope and a large upstream area. These model results can aid in the design and siting of water protection measures within the drained area.

Abstract. Drained peatlands are one of the main sources of carbon dioxide (CO2) emissions globally. Emission reduction and, more generally, ecosystem restoration can be enhanced by raising the water table using canal or drain blocks. When restoring large areas, the number of blocks becomes limited by the available resources, which raises the following question: in which exact positions should a given number of blocks be placed in order to maximize the water table rise throughout the area? There is neither a simple nor an analytic answer. The water table response is a complex phenomenon that depends on several factors, such as the topology of the canal network, site topography, peat hydraulic properties, vegetation characteristics and meteorological conditions. We developed a new method to position the canal blocks based on the combination of a hydrological model and heuristic optimization algorithms. We simulated 3 d dry downs from a water saturated initial state for different block positions using the Boussinesq equation, and the block configurations maximizing water table rise were searched for by means of genetic algorithm and simulated annealing. We applied this approach to a large drained peatland area (931 km2) in Sumatra, Indonesia. Our solution consistently outperformed traditional block locating methods, indicating that drained peatland restoration can be made more effective at the same cost by selecting the positions of the blocks using the presented scheme.

Continuous cover management on peatland forests has gained interest in recent years, in part because the tree biomass with significant evapotranspiration capacity retained in selection cuttings could be used as a tool to optimize the site water table level (WTL) from both tree growth and environmental perspectives. This study reports WTL responses from six field trials established on fertile Norway spruce-dominated drained peatland forests across Finland. At each site, replicates of different intensity selection cuttings (removing 17-74% of the stand basal area) or clear-cut in parallel with intact control stands were established and monitored for the WTL for 2-5 postharvest years. The observed WTL rose after selection cuttings, and the response increased with harvest intensity and depended on the reference WTL; that is, larger responses were found during dry summers or in more southern location. Selection cuttings removing about 50% of the stand basal area raised the WTL typically by 15-40%. Using a process-based ecohydrological model, tested against data from the field trials, we show that the role of tree stand in controlling the WTL clearly decreases along the latitudinal climate gradient in Finland. This suggests that the potential of controlling WTL using selection cuttings is more prominent in southern than in northern Finland. Predictions with future climate (2070-2099) further indicated a general decrease of the WTL and that the importance of the tree stand in controlling the WTL will increase, especially in northern Finland. The results overall thus suggest that selection cuttings can be used as a tool to control the WTL in boreal drained peatland forests, and the potential is likely to increase in future climate.