Tatjana Kuznetsova

The reclamation of the North Estonian oil shale mining area

The restoration of post-industrial landscapes is often a challenge regarding multifunctional land use issues. Multifunctionality is important from the point of view of both natural capital and socio-economic values (Haines-Young et al. 2006). On the other hand, restoration provides several opportunities for the optimal use of landscape functions (de Groot 2006). In this paper we analyse opportunities for the further multifunctional use of the oil shale mining region in North-Eastern Estonia.

Use of biofuel ashes in forestry

Bioenergeetikas tekkivate jäätmete kasutamine metsanduses Negative environmental impacts of fossil fuel combustion have increased the use of biomass for energy production. As a consequence of the increased use of biofuels, the production of ashes will increase greatly in the near future. Because of relatively high contents of plant nutrients, biofuel ashes can be recycled as mineral fertilisers to compensate for the loss of nutrients resulting from tree harvesting. The present review aims to summarise the available information on factors affecting the quality of the wood and peat ash and the implications arising from ash application as fertiliser in the forest ecosystems. The understanding of the wood ash as fertiliser originates from the traditional slash-and-burn agriculture. During combustion most elements in wood are retained in the ash. The quality and chemical composition of ashes depends on many factors. The major elements in the ashes are calcium, potassium, magnesium, manganese, sodium, iron, phosphorus and sulphur. Trace elements found in different ash include barium, boron, cadmium, copper, mercury and zinc. The most abundant elements in peat ash are silicon, iron and aluminium. Ashes are characterised by high alkalinity with pH in the range from 11 to 13. Ashes raise the pH and reduce the total acidity in the humus layer and in the top of the mineral soil. The addition of wood ash does not result in a significant growth increase on mineral soils but increases the tree growth on peat soils. The Cd in wood ash did not become bioavailable and harmful to forest biota. The application of wood ash did not change or even decreased the 137Cs activity within forest soil. Wood ash application increased the coverage of the ground vegetation in upland forests and on peatland. Increase in microbial activity and growth rate after ash treatment was observed. Use of biofuel ashes in forestry The positive effect of wood ash on plant growth was understood long ago as better growth of grasses on areas burnt by natural fires was noticed. Scientific study of the effects of ashes began in the first half of the 20th century when the fertilisation experiments with wood ash were started in Sweden (1918) and in Finland (1937). Experiments of fertilisation with wood ash of drained peatlands in Finland are classical and the plots are used for studies up to now. The quality and chemical composition of ashes depends on many factors, including type of the fuel, tree species, type of the plant tissue, degree of the processing of the fuel before combustion, type of the burner and incineration conditions, and proportion of bottom and fly ash in the end product. The major elements in the ashes are calcium, potassium, magnesium, manganese, sodium, iron, phosphorus and sulphur. Ash is generally low on nitrogen because it is vaporises during combustion. Trace elements found in different types of ash include barium, boron, cadmium, copper, mercury and zinc. Compared to wood ash, peat ash contains essentially less mineral elements. The most abundant elements in peat ash are silicon, iron and aluminium. Ashes are characterised by high alkalinity with the pH ranging from 11 to 13. When applied to a soil, ashes will raise its pH and reduce the total acidity in the humus layer and in the top of the mineral soil. A rise in the concentration of base cations has been reported. Wood ash application has been found to increase the levels of extractable phosphorus in humus layer when higher ash doses are used and has little impact on total nitrogen concentrations in soil due to its low levels in the ash. The addition of wood ash does not result in a significant growth increase of trees on mineral soils. The limiting factor for tree growth on mineral soils is in most cases the availability of nitrogen. Wood ash promotes the growth of trees and improves the growth conditions on peat soils, and these positive effects are long lasting. Application of low peat ash doses did not increase the biomass production of trees but has a positive effect when larger amounts are applied. The effects of cadmium on ecosystems and a hazard to human health are of particular concern. There is currently not enough scientific knowledge available to recommend restrictions on the wood ash use as forest fertilizer due to high cadmium concentrations. Generally, the cadmium in wood ash did not become bioavailable and harmful to forest biota. Radionuclide content of forest biomass harvested for energy is related with wood ash application. Results based on experiments show that the application of wood ash does not change or even decreases the 137Cs activity within forest soil and vegetation. On peatlands an increase in the coverage of herbs and grasses and colonisation by nitrophiles has been observed. In addition, sphagnum mosses are substituted by forest mosses. However, wood ash may cause burn damages to bryophytes and lichens. According to some published data, the effect of wood ash on fauna consists in changes in the concentrations of heavy metals and radionuclides in body tissues. In most wood ash studies increased microbial activity and growth rate after ash treatment are reported.

Short-Term Influence of Clinker Dust and Wood Ash on Macronutrients and Growth in Norway Spruce (Picea abies) and Scots Pine (Pinus sylvestris) Seedlings

The effects of clinker dust and wood ash on Norway spruce and Scots pine seedlings were compared in buried pots. Clinker dust (0.5 kg m−2) and wood ash (0.5 kg m−2) were applied to the surface of a nutrient-poor mineral soil. In the second year, the increase in soil pH by the dust and ash were larger than in the first year. Both alkaline treatments caused a large increase in the needle potassium (K) concentration. An excess of soil K relative to magnesium (Mg) was observed by decreased Mg concentration in needles shortly after treatment. However, Mg concentration in needles stayed in the sufficiency range. Current results confirmed earlier findings that despite a positive effect on base cation nutrition, wood ash has a low potential for increasing the biomass of forest stands on mineral soils due to the N limitation in these soils.

The ecological status of Puhatu cutover peatland

Puhatu ammendatud jääksoo ökoloogilisest seisundist The aim of the present study was estimation of the ecological status of Puhatu cutover peatland in Norteast Estonia. Results of the samples showed that the pH of peat in Puhatu cutover peatland was in the range 5.1-5.5. The nutrients concentrations of peat (%) varied as follows: total N 2.1-2.9, total P 0.016-0.032, K 0.004-0.02, Ca 1.2-3.5 and Mg 0.08-0.2. The height of pines was 3.0 ± 0.6 m and height growth in current year was up to 73 cm. Comparison of our results with the scale presented by Ingestad suggests that the content of P, K and Mg in pine needles and birch leaves is lower and Ca content significantly higher than the optimum level. The ecological status of Puhatu cutover peatland Differently form fields left to lie fallow or forest clearings, vegetation on cutover peatlands is not restored for a very long period of time because the original vegetation has been destroyed and the conditions for the germination of seeds and growth of plants are unfavourable. As the vegetation has been destroyed no photosynthesis occurs in cutover peatlands and so carbon dioxide is not bound any more. Therefore, reclamation of cutover peatlands is of vital importance from the standpoint of environmental protection. Analysis of the samples showed that the pH of peat in Puhatu cutover peatlands was in the range 5.1-5.5. The nutrient concentrations of Puhatu peatland peat (%) varied as follows: total N 2.1-2.9, total P 0.016-0.032, K 0.004-0.02, Ca 1.2-3.5 and Mg 0.08-0.2. The height of pines was 3.0 ± 0.6 m and height growth in current year was up to 73 cm. Comparison of our results of pine needles (100N: 2P: 11K: 13Ca: 3Mg) and birch leaves (100N: 4P: 19K: 14Ca: 6Mg) with the scale presented by Ingestad (scale for pine 100N: 14P: 45K: 6Ca: 6Mg; scale for birch 100N: 13P: 65K: 7Ca: 8,5 Mg) suggests that the content of P, K and Mg in pine needles and birch leaves is lower and Ca content significantly higher than the optimum level. Correlation analysis revealed a statistically significant relationship between mineral elements content (total N, total P, K, Ca and Mg) in pine needles and in peat. For birch significant correlation was established between K, Ca and Mg content in leaves and in peat. As cutover peatlands suffer shortage of nutrients, one of the ways for improving growth conditions of trees and accelerating their growth would be to add peat or wood ash to the growth substrate. The high concentration of P and K in wood ash is of special importance, which creates preconditions for N assimilation and forestation of cutover peatlands. Investigations conducted in Finland showed that the use of wood ash to amend peat soils is promising. Better results in using biofuel ashes to stimulate tree growth have been achieved in peat soils because wood ash contains all elements necessary for tree growth except N. This vitally important element is limiting to tree growth on mineral soils where its content is low, but peat soils contain sufficient amounts of this nutrient while other mineral nutrients are in short supply.