Leo Heikurainen. (1957). Metsäojien syvyyden ja pintaleveyden muuttuminen sekä ojien kunnon säilyminen. Acta Forestalia Fennica vol. 65 no. 5 article id 7468. https://doi.org/10.14214/aff.7468

English title: Changes in depth and top width of forest ditches and the maintaining of their repair.

Original keywords: ojitus; metsäojitus; suot; ojat; ojien kunto; ojansyvyys

English keywords: drainage; peatlands; draining of peatlands; ditches; ditch depth; ditch repair

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The article deals with forest ditches dug by manual labour in drained peatlands in Central and Southern Finland, ranging in age from 16 to 25 years. The ditches have been allowed to develop in a natural state. A total 1,160 of randomly selected sample plots were studied.

The results show that the originally dug ditch depth has not been the decisive factor from the viewpoint of maintaining the ditch repair. Ditches dug in thick peat layer have maintained their repair better than those dug in thin peat layer. Apparently, the influencing factor is the type of soil, to a certain extent parallel to the thickness of peat layer. In ditches dug mainly in mineral soil, the type of soil has essentially contributed to maintaining the ditch repair. Ditches in coarse-grained soils maintained a better repair than those in fine-grained soils. Also, the steeper the gradient of the ditch the better the ditch repair has been maintained. There was no relationship between the thickness of peat and the filling up of ditch bottom, because of the influence of mineral soil. Filling up of a ditch seems to be mainly due to the sinking of peat. The filling up of ditch bottom was more pronounced in clay-silt soil than in other soil types. The filling up of ditch bottom by varying gradient is due to the fact that with a small gradient the speed of water is so slow as to permit the soil particles to sink to the bottom. Another factor affecting filling up of the ditches is wetness of the peatland. Deepening of ditches happens mainly through erosion, if the gradient is large enough. The study suggests that a 50-m spacing with about 60-cm ditchc depth would be most profitable.

The PDF includes a summary in English.

Heikurainen, E-mail: lh@mm.unknown

article id 7614, category Article

Leo. Heikurainen. (1980). Kuivatuksen tila ja puusto 20 vuotta vanhoilla ojitusalueilla. Acta Forestalia Fennica no. 167 article id 7614. https://doi.org/10.14214/aff.7614

English title: Drainage condition and tree stands on peatlands drained 20 years ago in Finland.

Original keywords: mänty; tilavuuskasvu; ojitetut suot; sarkaleveys; ojien kunto; pohjaveden pinta; ojasyvyys

English keywords: Pinus sylvestris; Scots pine; stand volume; ditch spacing; ditch depth; volume increment; groundwater depth; ditch condition

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The aim of this investigation was to examine the dependence of stand volume and increment on different growth factors on drained peatlands drained 20 years ago. Measurements were made in 1977-79 on 35 sample plots in Central Finland on relatively poor pine bogs with a thick peat layer.

It became evident that the stand volume, increment and radial growth and growth development are primarily functions of groundwater depth. Groundwater depth is dependent, in the first place, on ditch depth and ditch condition. With regard to the variation in ditch spacing (ca. 35-70 m) under examination, the effect of ditch spacing on the stand was insignificant. As a practical recommendation it was concluded that ditches should be kept deep enough (> 70 cm) in order to maintain undisturbed stand development.

The PDF includes a summary in English.

Heikurainen, E-mail: lh@mm.unknown

Category : Research article

article id 25025, category Research article

Mikko T. Niemi, Marjo Palviainen, Annamari Laurén. (2026). Enhanced multi-objective decision support in peatland forestry using Peatland simulator SUSI. Silva Fennica vol. 60 no. 2 article id 25025. https://doi.org/10.14214/sf.25025

Keywords: forest planning; drainage; tree growth; nutrient leaching; trade-offs; ditch depth; greenhouse gas emissions

Highlights: Reaching multidimensional economic and environmental objectives in peatland forest management can be enhanced using process-based ecosystem models; Applying ditch depth of 60 cm in ditch network maintenance improved the trade-off between timber production and soil greenhouse gas emissions compared with the conventional ditch depth of 90 cm; Intensive drainage can reduce tree growth in southern Finland during dry summers.

Abstract | Full text in HTML | Full text in PDF | Author Info

Boreal peatland forests have been extensively drained to increase timber production, but the maintenance of shallowed ditches has been questioned due to increased greenhouse gas (GHG) emissions and negative impacts on water quality. Ditch network maintenance (DNM) lowers water table, which typically increases tree growth, but also increases rate of peat decomposition and consequently CO₂ emissions. Multi-objective forest planning balances between the conflicting economic gains and adverse environmental impacts. We used a process-based Peatland simulator SUSI to simulate three management scenarios for 20 forest stands, covering the variety of growing conditions in Finland. We studied how DNM with a reduced ditch depth (60 cm) and a conventional ditch depth (90 cm) affected stand growth, GHG balance, and nitrogen and phosphorus export. Over a 20-year simulation period, annual volume growth response was on average 0.8 m³ ha^-1 when ditch depth was changed from 30 cm to 60 cm and 1.0 m³ ha^-1 when ditch depth was changed from 30 cm to 90 cm. In southern Finland, DNM decreased stand growth in fertile sites. Soil GHG emissions increased on average by 49% and 119% in 60 cm and 90 cm ditch depths, respectively, compared to 30 cm ditch depth. The cost of reducing GHG emissions ranged from 0–22 € per ton of CO₂ in our study sites and scenarios. Our results support the idea that omitting DNM or reducing ditch depth may lead to acceptable compromises, as the marginal cost of soil GHG emissions considerably increases with increasing ditch depth.

Niemi, Department of Forest Sciences, University of Helsinki, 00014 Helsinki, Finland; School of Forest Sciences, University of Eastern Finland, 80101 Joensuu, Finland https://orcid.org/0000-0003-0461-3667 E-mail: mikko.t.niemi@helsinki.fi
Palviainen, Department of Forest Sciences, University of Helsinki, 00014 Helsinki, Finland https://orcid.org/0000-0001-9963-4748 E-mail: marjo.palviainen@helsinki.fi
Laurén, Department of Forest Sciences, University of Helsinki, 00014 Helsinki, Finland https://orcid.org/0000-0002-6835-9568 E-mail: annamari.lauren@helsinki.fi

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