At the same time, yields of cucumber, tomato, gerbera and rose have risen many-folded (Tahvonen 2004).
New trends in the use of peat.
Today peat is also used to produce textiles for clothing and footwear and the therapeutic use of peat and peat extracts has developed into an art (Korhonen 1996, Pirtola 1996). Peatlands also offer habitats for a diverse and specialised flora and fauna (Aapala et al. 1996) which means that more of them should be officially preserved. Especially spruce mires are underestimated in conservation areas. Also, 90% of mire conservation areas are situated in northern Finland (Aapala et al. 1996).
Peatland tourism is a growing new way of utilizing peatlands. There was even an EU Life-project working on this during 2002-2005 in Finland (Wiiskanta & Lipponen 2005). They proposed a lot of new activities besides old ones. For example, excursions based on mire myths, aesthetics of peatlands, bird watching trips etc. All these utilize pristine mires which urge their protection but also careful planning not to destroy or disturb the characteristics that the tourists have come to see. Until now we have several sport happenings in Finnish peatlands : swamp soccer, swamp volleyball, swamp hockey, swamp hiking.
Besides peatland berries (Salo 1996) there are also other commercially interesting plants on mires. For example, Drosera rotundifolia has growing markets in central Europe in medical industry. Each year two tons of fresh Drosera plants have been exported from Ostrobothnia region. There are also cultivation trials of Drosera conducted by the Agricultural Research Centre in Finland. The yield has been noted to be 50 times higher than on natural mires and the chemical contents of cultivated plants to be similar with the natural ones (Galambosi et al. 2000). Besides Drosera, also Myrica gale would have huge markets in central Europe.
Peatlands used for forestry.
The earliest peatland drainage operations in Finland took place during the famine years (1866-1868). Then the target was to provide work for the unemployed and to occupy new arable land. More systematic drainage aimed at increasing the growth of tree stands on peat soils or wet mineral soils started in state- and industry-owned land in1908. The private sector started forest drainage activity in 1928 when the first Forest Improvement Law was introduced. Forest improvement legislation directing government subsidies and low-interest loans to private forest owners has had a decisive impact on the level and scope of forest drainage in Finland (Pivnen & Paavilainen 1996).
Forest drainage activity developed into a nation-wide campaign to increase forest growth in the 1970s. The area annually drained increased steadily up to 1969, when 295 000 ha was drained. The total forest drainage area according to the forestry statistics is about 6,0 million ha. The real area of drained peatlands is, however, smaller because forestry statistics include old drainage areas, which have had complementary ditching and thus have been counted twice. On the other hand, the area of forest drainage in national inventories is too small as some of the peatlands originally drained for forestry have been cleared for agriculture or peat harvesting and some of the drained sites with a shallow peat layer have been later classified as drained mineral soil (Pivnen & Paavilainen 1996). According to the latest inventory (Hkk et al.
2002) the area drained for forestry in Finland is approximately 5.7 million ha of which 4.6 million ha are drained mires and 1.1 million ha are drained mineral soils which probably have been originally thin-peated.
Drainage and fertilization of mires and peatlands have considerably increased the total volume and annual increment of peatland forests. According to the National Forest Inventories (NFI) the total volume and increment of peatland forests have developed since the beginning of 1960s as follows:
Standing volume Total annual increment mill. m3 mill. mNFI 3 (1951-53) 91 9.NFI 7 (1977-84) 291 14.NFI 8 (1986-94) 365 17.The increase would be even higher if the effect of ditching on tree growth before NFI3 (1951-53) is considered, as well as, the growth increase on those originally shallow-peated sites which have later been classified as mineral soils. It can therefore be estimated that the increase in the annual increment caused by forest amelioration on peatlands in the middle of 2000s exceeded 10 million m3. It should, however, be noticed that the increase in total stand volume and annual increment is not dependent only on the ameliorative effect of drainage and fertilization but also on the small amounts of cuttings (Pivnen & Paavilainen 1996).
The problem in practical peatland forestry has been that the cuttings realized are far away from the plans and calculations made by forest authorities and researchers. In NFI 8 it was estimated that there would be need for cuttings on 2.35 million ha during the next ten year period. Similarly it was estimated that complementary ditching would be needed on an area of 1.5 million ha which is higher figure than was presented in the Finnish National Forest Program (Hkk et al. 2002).
Restoration of peatlands drained for forestry.
Needs and aims of restoration. Peatland restoration aims to revitalize a self-sustaining naturally functioning mire ecosystem which accumulates carbon and retains nutrients from through-flowing waters (e.g. Wheeler and Shaw 1995). The first step is to raise the water table and ideally stabilize water table level close to peat surface. In successful restoration, the recolonization of mire plant species follows rewetting, and finally, the carbon cycle typical of the mire ecosystem, including anoxic decomposition, begins once again (Pfadenhauer and Kltzli, 1996).
The aims of restoration of peatlands drained for forestry are diverse. As forestry is most profitable on nutrient-rich peatland sites (Paavilainen and Pivnen 1995), those sites have been selected for drainage first, and thus are now the rarest in pristine condition. Nutrient-rich mires have threatened species requiring habitats with flowing water having often also a special landscape value (Aapala et al. 1996, The principles.... 1999, Virkkala et al., 2000). One type of mires that has been used intensively for agriculture and forestry, is the spruce mires which can be found as narrow strips in the ecotone between forest and mire ecosystems. These ecotones are ecological hot-spots for biodiversity (Aapala et al. 1996) but may be easily destroyed by a single ditch and even have often been left out of the nature conservation areas. Drainage in these ecotones diverts waters from the seemingly natural mire area and affects its natural state. The need for restoration is very high in spruce mires in hemiboreal and southern boreal zones, where (data from Finland) less than 1% of them have been protected, and almost half of these protected spruce mires have been drained (Virkkala et al. 2000).
Other priority sites to be restored include areas with special landscape value where the natural mosaic of dense forests and open or sparsely treed mires should be returned. Also, the need to create buffer zones between terrestrial and water ecosystems to capture liberated nutrients from the forestry operation areas can be achieved by restoring small areas of peatlands drained for forestry (Sallantaus et al. 1998).
Restoring drained peatlands to promote landscape and species diversity.
The planning for peatland restoration should be done on peatland ecosystem level. Attempts should be made to restore the hydrological aspects of the whole watershed including mineral soil and peat covered areas, although this is often difficult due to the local land ownership conditions (Aapala and Lindholm 1999).
In recently drained areas, it is likely that restoration reverts the area to its original habitat type. The longer the area has been drained, the more difficult it is to fully recreate the original state. In such cases, successful restoration leads to a “new natural state”, different from the original, but nevertheless recognizable as some other peatland habitat type (Heikkil and Lindholm 1996, The Principles...., 1999).
The restoration of hydrology is achieved by damming or filling in the ditches (Vasander et al. 1992, Heikkil and Lindholm 1995). Drainage has caused peat subsidence to be the most pronounced near the ditches (Minkkinen and Laine 1998). Thus, water may continue to flow along or stay in the dammed or filled-in ditches, instead of spreading across the mire. Therefore, appropriate water conditions for the initiation of restoration processes are difficult to reach, and the result is usually a mosaic of drier and wetter areas much unlike to the moisture conditions in pristine peatlands. Also the fluctuations of the water table are expected to increase due to the increased bulk density of the surface peat after drainage (Minkkinen and Laine 1998). Extending dams several meters to the sides of the ditches will spread the water flow more evenly across the mire (Sepp et al. 1993). Hand-made dams are expensive and very often do not hold water in peatland. That is why excavators are usually used in damming or filling-in the ditches (Sallantaus et al. 2003).
Tree stands which have developed since drainage can be removed partially or totally. In peatlands which originally had a dense tree cover, particularly spruce mires, the whole tree cover is usually left intact during restoration (The Principles....1999). This will increase the amount of windfalls and decaying wood on the site increasing the future fungi and insect biodiversity. On topographically flat areas large stands of dead trees may be formed. If the tree stand is manipulated, typical characteristics of pristine spruce mires, such as long continuity, trees of all sizes and ages, large amounts of dead wood and gap-phase dynamics (Kuuluvainen 1994, Hrnberg et al. 1998) should be taken into account. Restoring the hardwood component of the natural tree stand structure is usually not a problem since birches as pioneer tree species, readily recolonize restored habitats. The structure of pre-drainage tree stands may be clarified with the aid of old air photos. On peatlands which were treeless before drainage the whole tree layer is usually cut and taken away. On ombrotrophic peatlands, also the slash might be taken away to diminish the amount of nutrients left on the site.
Vegetation recovery after restoration in peatlands drained for forestry is usually fast after rewetting as diaspores of mire plants are nearby (Jauhiainen et al. 2002). No seeding or planting is needed contrary to the situation on large cut-away peatlands (e.g. Sliva and Pfadenhauer 1999, Rochefort 2001).
However, species compositions in pristine and restored sites may remain to be different for a long time (Soro et al. 1999).
Changes in water quality after restoration. Before large-scale forestry drainage, the discharged water from forested peatlands was naturally filtered through the existing peat deposit. The even topography, dense moss cover and the favourable physical, chemical and biological properties of surface peat (e.g. anoxia, porosity, cation exchange capacity, and microbial retention) facilitate versatile buffering functions in these systems. As a result of forest drainage, the major part of these buffering systems has been lost. Restoring drained peatlands, being potentially well suited to act as buffer zones between forestry land and a watercourse, is an important reason for rewetting outside nature reserves (Sallantaus et al. 1998). These restored buffer zones are important in reducing the nutrient loading (especially N and P) imposed on watercourses from the forestry operation areas (Hyvnen et al. 2000, Silvan et al. 2002, 2003a,b).
Restoration has also been noted to cause an immediate increase in phosphorus concentration in the outflow (Sallantaus 1999, Vasander et al. 1988, Vasander et al. 2003). Drained peatland forests have often been fertilized with phosphorus, and in the restoration site, felling slash has been left on the site. Although mires were restored in late fall or early winter, the increase in phosphorus concentration may take place late in the summer and in early fall, showing that biological processes are involved, directly or indirectly, to the phosphorus release. As water level is raised abruptly, phosphorus bound in roots and mycorhizae may be released due to anoxic conditions (Sallantaus et al. 2003). Very high concentrations of phosphorus may occur especially during the low flow periods, up to more than 1000 µg/l. However, three years after restoration, average P concentrations in runoff dropped down to below 50 µg/l. The maximum annual phosphorus load due to restoration was on the order of one kg of phosphorus per restored hectare, based on the results of the catchments monitored in Seitseminen National Park, southern Finland (Sallantaus 1999). Thus it seems that the increase in P concentration is only of short duration compared to the age of the buffer zone.
Also other changes in water quality take place after restoration.
Leaching of dissolved organic carbon increases for some time after restoration, when increased amounts of water reach the decomposed surface peat of the drained area. The higher concentrations of organic acids increase the acidity of runoff waters as well, and the increased acidity may be the reason, why the establishment of so called brown mosses (Amblystegiaceae) is very poor after restoration of sites where they used to thrive in the natural state (Sallantaus 1999).
Silvan et al. (2002, 2003a,b) noticed that a restored peatland was very effective in retaining N and P. Approximately 15 % and 25% of experimentally added high loads of N and P, respectively, were retained by microbes while the retention by vegetation was 70% for N and 25% for P.
Karsisto et al.(2003) noted that the concentrations of dissolved carbon and iron in the smallest molecular size fraction and iron also from high molecular compounds were lower after the water had passed this restored area. These promising results show that whenever possible each drainage area should include a restored buffer zone through which the outgoing waters from the drainage area and the surrounding upland forest catchment would be filtered.
Future needs in research and monitoring. The first experiences of restoration are quite promising. The forestry drained peatlands restored are, however, in their very early stages of post-restoration succession and many questions remain. Practical restoration projects should be closely linked with monitoring and research whenever possible (Heikkil and Lindholm 1997, Principles.... 1999). Restoration of nutrient-rich peatlands might not be easy since changes in mire vegetation and peat properties are most pronounced after disturbance. Restored habitats will be colonized by their typical species most likely if restored fragments are close to existing sources of potential colonists (Campbell and Rochefort 2003). So sites where targeted plant and animal species still exist in the surroundings should be prioritized for restoration. Monitoring enables to correct future actions in order to better achieve the restoration goals (adaptive management, Walters and Holling 1990). Incorporation of research into management generates synergy benefits, for example, by enabling to set up experiments at scales that are relevant both ecologically and for management.
This also helps to ensure the formation of a knowledge basis about the long-term effects of restoration, which in turn can be used in planning future restoration efforts (Kuuluvainen et al. 2002). Other questions concerning the restoration of peatlands drained for forestry are linked with physico-chemical changes in the surface peat and changed hydrology after restoration. Also the metapopulation dynamics of specialized mire animals (e.g. butterflies) and rich fen vascular plants should be known better to ensure that restoration activities lead to successful results (Rassi et al.
References Aapala K., Lindholm T. 1999. Suojelusoiden ekologinen rajaaminen. (Abstract:
Ecological evaluation of the boundaries of protected mires). Metshallituksen luonnonsuojelujulkaisuja. Series A 95.
Aapala K., Heikkil R. & Lindholm T.1996. Protecting the diversity of Finnish mires. In: Vasander H (ed), Peatlands in Finland. Finnish Peatland Society, Jyvskyl, pp:45-57.
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