Suo - Mires and peat vol. 30 no. 2 | 1979

In the study, comparisons were made between the decomposition degree of peat deternimed in accordance with GOST-10650-72 standard, and DTG peaks for peat. When a peat sample of 15 mg and a heating rate of 10°C/min were used, peaks were observed in temperature areas of 310 to 325°C and 415 to 435°C. The former area presents the oxidation of sugars and cellulosic material. The height of the peak correlates with the degree of decomposition, the correlation coefficient being —0,92 (n=10). When the decomposition values were compared with the height of the peak in the area of 415 to 435°C, a value of 0,73 was obtained for the correlation coefficient. When the ratio of the peak heights was compared with the decomposition degree, a value of —0,94 was obtained. Hence- the decomposition degree of peat can be determined fairly reliably by aid of thermogravimetric measurements, if the contents of thermal changes are known adequately accurately.

• Ranta, Sähköposti: ei.tietoa@nn.oo

The root systems of rooted Scots pine and Norway spruce seedlings were kept in slow-flowing or stagnant ditch water for periods of varying length during different seasons. In the snowless period, the "flood" lasted from one week to three months. The seedlings were planted immediately after they hade been removed from water. If the treatment was started early in the spring before the beginning of root activity, both pine and spruce seedlings survived even if the treatment lasted until beginning of August. However, slight negative effects in growth and general development were observed. During late summer and autumn, pine and spruce seedlings appeared to suffer much more of temporary "flooding"" treatments than in spring and early summer. A treatment period of 2—3 weeks often was detrimental to a seedling. Norway spruce seedlings were less resistent in this respect than Scots pine seedlings. In November when soil temperature is approaching 0°C in Southern Finland, artificial flooding still caused damage to spruce seedlings. Part of the seedlings included in the experiments were kept in water throughout the winter. The effect of the treatment on the seedlings depended on the degree of ice formation in the water reservoir. If only a thin ice cover was formed (slow-flowing water), leaving major part of the root system in liquid water, both pine and spruce seedlings survived quite well; only a slight decrease in growth was observed during the following growth period. Instead, if the whole root system was surrounded by solid ice (stagnant water), more negative influences were observed, especially in the case of Scots pine. Also in the case of Norway spruce, a considerable decrease in growth during the next growing season was detected. Analogous experi-mets with larger individuals of the same two species (Pelkonen 1975, 1976 have shown corresponding results. "

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

• Heino, Sähköposti: ei.tietoa@nn.oo

The paper gives preliminary results of the initial development of lodgepole pine (P. contorta var. latifolia, provenance: Wono-won, British Columbia, Canada, 56°10'N; 121°30'W; 800—1000 m above sea level), compared with that of native Scots pine (P. sylvestris) in a planting experiment on a drained small-sedge bog nine years after planting in 1969. The experimental field is situated in Central Finland (61°50'N; 24°14'E; about 165 m above sea level). The annual rainfall is about 600 mm and that of the summer months (June-September) about 280 mm. Annual evapotranspiration is approximately 300 mm. The experimental field is divided into three areas (blocks), in which different drainage systems (ditch types) were used. In each area there are 8 sample plots, with 300 transplants in each, making a total of 24 plots and 7200 transplants of both pine species in the experiment. Area A is drained using ordinary open ditches, area B using plastic pipe drains and area C using narrow, vertical-walled ditches. Hyd-rological measurements were carried out in the areas in the years 1968—72 and the results have been previously published by Päivänen (1976). According to the results it was found out that the drainage effect of the plastic pipe drains was clearly smaller than that of the other ditch types, i.e. the water table in area B remained some 10 cm nearer the peat surface than in the two other areas. This affected the growth of the transplants so that the growth rate of both tree species studied, especially that of Scots pine, was in area B clearly slower (statistically significantly) than in areas A and C (Fig. 1). The height development of Pinus contorta during the first nine years since planting clearly exceeded that of P. sylvestris, except for area C (deep, narrow, vertical-walled ditches and seemingly slight-ly better nutrient status, because the amount of Sphagnum fuscum hummocks in this area was smaller) where Scots pine grew significantly better than in other areas (Fig. 1, Table 1). Lodgepole pine was 9 years after planting, on the average, in area A 31 %, in area B 24 % and in area C 5 % taller than Scots pine. This is in accordance with the results obtained in other studies with similar provenances (Hahl 1978). The mortality of transplants was also inventoried in summer 1978. The mortality of lodgepole pine turned out to be signi-ficantly smaller than that of Scots pine in all areas (Table 2). The proportion of dead Scots pine transplants was significantly higher in the poorly drained area B than in other areas, whereas Pinus contorta does not seem as susceptible to poor drainage. A new planting of both pine species took place in spring 1977 with the same experimental design and the mortality was inventoried in summer 1978. Table 2 shows that dying-off has been very small in both species confirming the results of the earlier planting (data group a in Table 2). The mortality of Pinus sylvestris was significantly bigger also in the latter planting (data group b in Table 2). The results of this experiment show that the early growth of suitable Pinus contorta provenances is somewhat better than that of Pinus sylvestris also in peatlands at least in circumstances described in this paper. It is also indicated (Fig. 1) that the requirements of lodgepole pine for drainage and nutrients may be smaller than those of Scots pine in peatlands.

• Laine, Sähköposti: ei.tietoa@nn.oo

The layout of a drainage system for a milled peat harvesting site is seen in Fig. 1. The ditch spacing used is 20 m and the ditches are about 1.5 m deep. However, sometimes it is necessary to use subsurface drains to increase the drainage effect of open ditches. In the rick areas at the end of the strips, where the harvested peat is stored, subsurface drains are the only method to drain the peatlayers. Eight different kinds of subsurface drains were tested in summer 1978 at Kaikonsuo (63°40'N, 26°40'E) peat harvesting field managed by The State Fuel Centre (VAPO). Two experimental fields were laid down: one in the strip area (Fig. 2) and the other in the rick area (Fig. 3). Five of the subsurface drain types used in the experiment were so called material drains: a board pipe drain with an inner cross-section of 64x102 mm (Fig. 8), and two sizes of plastic pipe drains (PVC) with an inner diameter of 40 and 65 mm. Two types of both drainsizes were used, one of which was bare (Fig. 9) the other covered with a filter material (Fibertix; Fig. 10). Three types of "nonmaterial" subsurface drains were tested in the experiment: a mole drain made with the Pajulahti Oy mole drain trencher (Fig. 4 and 5), a mole drain made with the VAPO mole drain plow (Fig. 6), and a narrow water furrow made with the Suokone Oy disc trencher. The ground water level in each drainage treatment was measured once a week. In the strip area, in each treatment, there were measuring wells in two rows; five in a row. In the rick area there were five wells in each treatment. In the strip area (Fig. 11) the distance to the ground water level in the control strips was about 50 cm. The mole drains or the narrow water furrows did not have any effect on the ground water level. The board pipe drains had the greatest lowering effect on the ground water level. In the strips with the plastic pipe drains the distance to the ground water level was about 80 cm. In the rick area the results obtained with the board pipe drain, with the mole drains and those of the control were similar to the results of the strip area. In the treatments drained with the plastic pipe drains the distance to the ground water level varied from 55 to 95 cm. The filter material did not increase the drainage effect of the pipe drains as expected, the case was rather the reverse. It would be necessary to continue the experiment to find out the duration of the drainage effect reached with the different kinds of subsurface drains and, after that, to make economical calculations on the profitability of the types of subsurface drainage studied.

• Menonen, Sähköposti: ei.tietoa@nn.oo
• Päivänen, Sähköposti: ei.tietoa@nn.oo