Suo - Mires and peat vol. 30 no. 4-5 | 1979

• Savolainen, Sähköposti: ei.tietoa@nn.oo

The effect of draining and fertilization on the radial and height growth of Scots pine has been studied on an ombrotrophic bog Laaviosuo in the vicinity of Lammi Biological Station. The study site represents a southern Finnish raised bog with Calluna vulgaris — Empetrum nigrum — Sphagnum fuscum -hummocks and Eriophorum vagi-natum — Sphagnum angustifolium or Sphagnum majus — S. balticum -hollows. Total thickness of the peat layer is 5—7 m with a 2—3 m of Sphagnum peat on the surface. Part of the bog (6 ha) was drained in 1966 and fertilized in 1970 (N as urea 100 kg/ha plus PK fertilizer 400 kg/ha). This study is part of a project concerning the comparative analysis of virgin and forest-improved mire ecosystems (Ruuhijärvi et al. 1979). Height growth of pines during 15 last years was measured with the accuracy of 1 cm from 37 trees in the virgin site, 23 trees in the site with only drainage and 27 trees in the drained and fertilized site during the autumns 1978 and 1979. In addition seven trees from a virgin dwarf shrub pine bog near the marginal slope of Laaviosuo were measured for comparison in the autumn 1978. Radial growth was measured in 1979 from 17, 10, 10 and 7 trees, respectively, with the accuracy of 0.01 mm. All the measured trees were selected randomly. At the same time we counted all the trees and seedlings from a sample area both in the virgin and fertilized sites. In the virgin bog the size of the sample area was 1.92 ha and in the fertilized area 1.60 ha for trees and 0.88 ha for seedlings. Height of all seedlings was measured with the accuracy of 10 cm and breast height diameter (d1.3) of trees with the accuracy of 1 cm. Growth of trees in the virgin bog site was very low: height growth about 3 cm and radial growth: 0.2 mm annually (Fig. 1, 2). In dwarf shrub pine bog the corresponding values were about 9 cm and 0.6 mm. Mere draining had very little effect (about 1 cm) on the height growth (Fig. 1.). Radial growth increased more clearly (Fig. 2). However, the figures exaggerate the situation because the trees have been measured very near the ditches (about 1—8 m). Trees which have grown at a distance of less than about 3 m from the ditches have incresed their radial growth, but others growing further away have not. This increases the variation as seen in Fig. 2. In practise, if this kind of ombrotrophic bog is drained fertilization with all macro-nutrient (N, P, K) is needed. Effect of fertilization is very similar on radial and height growth with the difference that height growth always reacts one year later (Fig. 1, 2). Maximum growth (about 35 cm and 3.2 mm) was reached in 1973 and 1974, respectively, after which the growth decreased almost as quickly as it had increased. In ombrotrophic sites the effect of fertilization is known to last less than ten years (Huikari & Paavilainen 1972 and Ipatiev & Paavilainen 1975). Only refertilization could possibly secure the continuing of tree growth. Fertilizing has changed also the size-classes of trees and seedlings (Fig. 5,6). Number of trees has increased from 470 per ha in the virgin area to 1390 per ha in the drained and fertilized area. The tree volume increment has been six-fold (from 1.3 to 8 m3/ha). Number of pine seedlings increased from 7100 per ha to 15300 per ha. There were also 2060 birch seedlings per ha in the fertilized area. Especially hollows have become stocked with seedlings. All these seedlings must compete with dense shrub layer for the nutrients but its effect on the mortality of seedlings can not yet be known. Mere draining seemed to have no effect on the population structure of seedlings. The present volume of the pine stand in the fertilized area, 8 m3/ha on average, is of the same magnitude as Heikurainens (1971) average values for virgin cottongrass pine bogs. However, drainage of cotton-grass pine bogs and Sphagnum fuscum pine bogs with so scarce pine stands seems to be economically questionable (Heikurainen 1973). Thus according to our results, even after the drainage and NPK fertilization the tree stand of this site type is still so low that the drainage and fertilization of such ombrotrophic pine bogs is probably unprofitable.

• Lindholm, Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo

The results obtained from old ash fertilization experiments established in Finland in the 1930's have shown that wood ash is ideally suited for forest fertilization. The aim of this study is to determine the changes which have taken place in the microbial population and decomposition of organic-matter in the peat of old ash fertilization plots. The area of Tohmajärvi, where the ash fertilization experiment was established in 1939, completely lacked tree cover at the time of fertilization. The total production of the tree stand which has developed since fertilization is about 300 m3/ha. The oldest ash fertilization experiment in the Nordic countries is located in Sweden. The total production of the tree stand growing in the Norra Hällmyren area (fertilized 1926) was about 200 m3/ha until the year 1973 (Holmen 1979). The annual growth of the tree stand on the corresponding unfertilized areas is below 1 m3/ha. The results of chemical analyses carried out on the peat from Tohmajärvi are shown in Table 1. The ash fertilization has decreased the acidity by such a small amount only that this alone could not account for the good growth rate of the trees. The total amount of nitrogen has decreased in the surface layer of the peat in the plots which have got ash fertilization. This indicates that ash fertilization has brought about the conversion of nitrogenous compounds in the peat into a form that can be utilized by the plants. Organic matter decomposition at Tohmajärvi has been studied by observing the decomposition of cellulose strips placed at different depths in the peat (Fig. 2). Decomposition was more effective at a depth of 40—50 cm on the fertilized plots than at a depth of 5—10 cm on the unfertilized plot. Bacterial determinations were carried out on peat samples taken from Tohmajärvi on the 9th August 1977. The results are shown in Fig. 4. The numbers of different types of bacteria at all depths studied were many times greater on the plot given ash fertilization than at corresponding depths in the unfertilized plot. Ash fertilization has had the clearest effect on the number of bacteria in the 10—20 cm deep peat layer. Bacterial determinations were carried out on samples taken from the Hällmyren ash fertilization plots on the 23rd August 1979. The results are presented in Fig. 5. Ash fertilization has had an increasing effect on the number of bacteria only in the 0—10 cm surface layer. The numbers of different types of bacteria decrease very steeply on passing deeper down into the peat. Ash fertilization has increased the pH in the Hällmyren peat by one pH unit, but only in the 0—10 cm surface layer. Both tree growth in Tohmajärvi and Hällmyren areas and the microbiological analyses which were carried out show that ash fertilization brings about a permanent ameliorative effect. In the study areas where ash fertilization is already over 30 and 40 years-old, tree growth is still good and the numbers of different types of bacteria higher than in the unfertilized plots. However, the tree growth in the Hällmyren area is not as good as that at Tohmajärvi. This may be due to the fact that the natural nutrient status at Hällmyren is not as good as at Tohmajärvi and drainage is clearly less effective. It should be born in mind that if ash is to be used for forest fertilization, then efficient drainage is also neccessary.

• Karsisto, Sähköposti: ei.tietoa@nn.oo

Different kinds of boron and copper fertilizers were applied to pine seedlings planted in a flark (see table 1). Three growth periods after the fertilization copper oxide, fertilizer boron, fritted boron, micro-nutrient mixture and bark ash gave better height growth than the control (NPK, Ca). Poorest results were achieved with the following micronutrients; solubor, copper sulfate, copper chelate and PK with Cu and B. The height growth in years 1978 and 1979 of only those seedlings that were fertilized with solubor was poorer than that of the control. The height growtht of fritted boron and bark ash fertilized seedlings was statisticaly significantly better than that of the control. The best result was achieved with copper oxide (Table 2). The comparison between the copper fertilizers revealed that copper oxide was the best copper compound for pine seedlings in a flark (Fig. 1). Fritted boron appeared to be the best boron fertilizer (Fig. 2). Bark ash was best of the nutrient mixtures studied (Fig. 3). The experiment showed a positive trend in favor of slowly dissolving micronutrient compounds, including bark ash, on pine seedling growth in a flark. It is also evident, that the commercial micronutrient fertilizers are by no means biologically the most effective compounds for pine seedling fertilization on peatland. In forestry and research commonly used coppersulfate and fertilizer boron seemed to be rather questionable as peatland fertilizers.

• Pietiläinen, Sähköposti: ei.tietoa@nn.oo
• Veijalainen, Sähköposti: ei.tietoa@nn.oo