Suo - Abstracts of Vol. 50, 1999

Pine nutrition was monitored after the application of  phosphorus and potassium fertilisers of different solubility in 12 experiments on drained mires in northern Central Finland. Ten experiments involved the following three treatments: (i) control, (ii) fertilisation with rock phosphate and potassium chloride, and (iii) fertilisation with apatite ore or enriched apatite and phlogopite. Two experiments focused on the fertiliser amount. In seven experiments needle samples were collected three times: 3-7, 11-14 and 16-19 years after fertilisation and in the others once or twice (after 10-17 years). The stands suffered from phosphorus and potassium shortage on the unfertilised plots.  Rock phosphate had raised the needle phosphorus concentrations slightly more than apatite by 5-7 and 11-14 years after fertilisation. By the last sampling apatite (16-19 years after) had raised the concentrations to about the same or to a higher level than rock phosphate. Potassium chloride raised  the concentrations more than phlogopite during the first few years after fertilisation but the situation had reversed  by 11-14 years. Five years later the change was even more pronounced. The needle potassium concentrations increased slightly with the increasing application amounts on the nitrogen-rich sites. Fertilisation with PK lowered the needle zinc, manganese, copper and boron concentrations especially on the nitrogen-rich sites.

Key words: Fertilisation, macronutrient, micronutrient, nutrition, peatland, Scots pine

The present study looked into the soil properties of twenty-four peat-based field by examining the 0-10, 10-20, 20-30 and 30-40 cm soil layers and the effect that soil properties have on the initial development of young stands of downy birch growing in Pohjois-Savo, southern Finland. Adding of mineral soil to peat-based fields and the decomposition and subsidence of peat had resulted in increasing the bulk density of the peat, especially in the tilling layer. Also, the amounts of nutrients in the tilling layer were higher than in the layer below. Together with fertilization, the addition of mineral soil had increased the soil's nutrient amounts manyfold compared to virgin mires and mires drained for forestry. Eighthy-one per cent of the trees were alive. The share of viable trees had fallen to half of the planting density, being now just 840 trees per hectar. The increase in the amount of extractable potassium and total copper in the soil improved the growth of young stands and reduced the proportion of trees of inferior quality. Growth disorders were observed in downy birch, and these were probably caused by increases in the ratios of the amounts of main nutrients and micro-nutrients in the soil. The ratio of nitrogen and phosphorus to copper was reflected best of all in the growth of young stands. An increase in the amount of soil nitrogen and phosphorus in relation to the amount of soil copper impaired stand growth and promoted the occurrence of trees afflicted by growth disorders.

Key words: peat-based field, bulk density, nutrients, nutrient relations, downy birch, growth disorder

Black spruce (Picea mariana, (Mill.) B.S.P.) has been traditionally managed as evenaged stands with artificial or natural regeneration on peatlands of northern Ontario Clay Belt region. However, lack of resources to make artificial regeneration on all clear-cuts and harvest methods unfavorable for natural regeneration often resulted in unsatisfactory regeneration. As a consequence, alternative management methods have been introduced for peatland black spruce, and this literature review discusses studies of these methods. In natural stands, both evenaged and uneven-aged structures may be found, while the second-growth stands originating from old horse-logging are mostly uneven-aged, with abundant advance growth. Currently, mechanized harvest with regeneration protection has been shown to sufficiently preserve residual trees and subsequently produce stands that are heterogeneous with respect to the size structure. In second-growth stands, uneven-aged management can be implemented with minimum diameter limits determined from stand structure and cut-to-length harvesting. Such management perpetuates a stand structure appropriate for uneven-aged management. Simulation study has been made to estimate black spruce yield under uneven-aged management with varying cutting cycle and minimum diameter limit. It seems that in some peatland sites uneven-aged management is a possibility to manage black spruce.

Key words: peatlands, Picea mariana, regeneration, stand management, stand structure, succession

This case study deals with the effects of forest drainage on six mire site types represented by 33 permanent sample plots within a Finnish aapa mire complex located in north boreal vegetation zone. We analysed the main compositional gradients, the abundances of plant species and the diversity of vegetation. The vegetation descriptions were made about at the time of drainage in 1933 and after that in 1943, 1950 and 1994. The forest drainage emphasized the importance of spruce mire and hummock-level bog influences (mire margin and mire expanse effects respectively) in controlling the structure of plant communities. The change of plant community was greatest on fertile mire site types, also spruce mire influence promoted the secondary succession. As expected, the shallow-rooted and/or demanding flark-level vascular plants and (eutrophic) fen mosses had not been able to adapt to the ground water level drawdown. At first, after drainage, species number, Shannon's H' and Simpson's D increased: many mire species of hummock and intermediate level microsites had increased while also pioneer and forest species had colonized the plots. By 1994, however, as the mire species were decreasing these measures had turned to decline except on the (most) infertile site types. Pielou's J' and the evenness based on D reacted vaguely, decreasing a little, though, from 1933 to 1994. Thus, in such cases the dominance in the vegetation had increased. The beta-diversity describing here the differences between plant communities (or site types) decreased along with the hydrological conditions becoming more uniform after drainage.

Key words: aapa mire, compositional gradients, fen, FUPGMA classification, GNMDS ordination, peatland vegetation

Widespread drainage measures, which were carried out mainly in the period 1950 - 90 on Finnish mires, have had significant climatic consequences, part of them being temporary, part permanent. The aim of this study was to prepare charts of these climatic effects by combining three sources of knowledge: 1) the climatic effect of drainage (e, oC), as given by (Solantie 1994, 1998) for a 100% mire area in the climatically most affecting stage, 2) fresh grid-square statistics of the proportion of drained mires compared with the total area, and 3) annual statistics of the proportion of drained mires in various stages having characteristic climatic effects, compiled by the Finnish Forest Research Institute. Three charts show the maximum cooling effect of peatland drainage in Finland during the first 15 years after the drainage in the period 1973 - 82, as drained mires in such a stage of drainage were then most common. Two charts show the warming effect after successful afforestation and canopy closure; the canopy acts as a radiation shelter and a mixing generator for the air beneath. In the middle boreal natural zone, that most heavily drained, the mean monthly minimum temperatures in the period 1973 - 1982 were reduced by 1.5 oC and the yearly frost-free period was shortened by 16 days. As a result of successful afforestation, the annual minimum temperature in the middle boreal zone will be raised by 2 to 3 oC by the year 2005.

Key words: climate, forestry drainage, mire

The effects of drainage maintenance on the nutrient contents in peat and Scots pine needles on drained pine mires were studied. The material consisted of twelve Finnish field experiments. Drainage maintenance (increasing ditching intensity; no treatment at all, mere ditch cleaning, mere complementary ditching, and both of them together) was carried out in 1982-1985. The needles were sampled in 1994-1995 and peat in 1996. There were great differences in the site types and consequently also in the peat and needle nutrient concentrations between the experiments. The needle Mn concentrations demonstrated a fairly good drainage status in all the treatments. Drainage maintenance had only minor effects on the nutrient status of peat and needles. Ditch cleaning decreased magnesium, manganese and zink amounts in the surface peat. Increasing the intensity of drainage maintenance increased the 100-needle dry mass, but decreased the needle boron concentrations. Peat and needle nitrogen concentrations increased slightly (not significantly) along with the increased intensity in drainage maintenance. The peat nutrients classified correctly 83.7% of the fertility classes for drained peatlands.

Key words: complementary ditching, ditch cleaning, forest drainage, needles, nutrients, peat, Scots pine.