Suo - Abstracts of Vol. 47, 1996

Time domain reflectometry (TDR) is a relatively new technique for measuring soil water content. It is based on measuring the apparent dielectric number (K_a) of the soil from the propagation velocity of an electromagnetic pulse travelling in the soil. Soil water content is then calculated from the apparent dielectric number. In this study, an empirical relationship between the apparent dielectric number and the volumetric water content was established for cultivated peat soils in the laboratory. A third-degree polynomial described the relationship with a coefficient of determination of 0.980 and a standard deviation of 0.027 m³m^-3. The relationship can be used to measure water content in typical cultivated Sphagnum and Carex peat soils in the range usually prevailing in the field, i.e. 0.3-0.8 m³m^-3.

Key words: dielectric number, water content

The effect of extraction time on the extraction of P, K, Ca, Mg and the effect of EDTA on the extraction of Mn, Fe and Zn with acid ammonium acetate was studied in 196 soil samples collected from afforested agricultural soils. Extraction time (1 hour or ca. 20 hours) did not significantly affect gravimetrically expressed mean concentrations of K, Ca and Mg in mineral soil samples. In peat samples the mean concentration of Ca and Mg with the shorter extraction time was 73% and 81% respectively of the mean concentration obtained with longer extraction time. The mean concentration of P with the extraction time of 1 hour was about 50% of the mean concentration obtained with the longer extraction time in peat and mineral soil samples. Extraction with acid ammonium acetate/EDTA extracted Fe sevenfold and Zn almost threefold compared with acid ammonium acetate alone. Regression models for converting gravimetric and volumetric nutrient values obtained with methods used in agriculture to gravimetric and volumetric nutrient values obtained with methods used in forestry are presented.

Key words: acid ammonium acetate/EDTA, peat, soil testing

Mire margin communities are mosaics of forest and mire vegetation which consist of several ecological guilds (forest, spruce mire, marsh and spring vegetation). Diversity patterns of undrained forested mire margin communities were examined by using numerical classification (TWINSPAN) and ordination (DCA) techniques. The understorey vegetation was tested for both alfa (species richness, Shannon H' and Pielou J diversity indices) and beta diversity (DCA dimensions). The structural diversity of the overstorey was examined by producing structural (TWINSPAN) clusters based on the percentage cover of tree and shrub species in six canopy layers and in one shrub layer. The study was based on the systematic sample plot data collected from permanent plots of the 8th Finnish National Forest Inventory (1985-86). The material consisted of 92 plots of undrained forested mire margin sites in south and central Finland (60^o-66^o). The alfa diversities between the seven site clusters differed more clearly than those between the site types. A considerable variety of species of different ecological guilds were found that represented the ecological sources of high beta diversity. Structural diversity varied between clusters formed from overstorey data.

Key words: boreal forest, peatland, structural diversity, vegetation diversity

The site index system presented is intended as support for the idea of developing a more hierarchical and integrated forest classification system in Finland. The data used were obtained from stands growing on old permanent experimental plots laid out in drainage areas in southern Finland. The model, describing the post-drainage development of stand dominant height as a function of drainage age (time elapsed since drainage), is based on successive measurement data (465 observations), collected from 89 plots, each representing a single stand. The site indices H40dr are post-drainage dominant height values 40 years since drainage, given in 2-meter classes. Post-drainage dominant height is defined as the difference between the current dominant height and the dominant height at the time of drainage. In classification work, one needs to know (or measure) the two aforementioned height characteristics, together with age since drainage. If the dominant height at the time of drainage is not known, it can be estimated from a function presented herein and based on current dominant height and drainage age. The mean annual volume increments at 40 years since drainage (MAI40) are also presented. There is still a need for examining separately the accuracy of the model with new data from spruce-, pine- and birch-dominated stands, collected for numerical constructions of site index curves. Therefore, the site index model and its characteristics must be seen more as outlines than as a final system for practical application. A well-functioning ditch network is a default when applying the site index curves.

Key words: drainage, growth and yield, site classification

Abstract: The study applies the combined use of the Delphi technique and the analytic hierarchy process to the assessment of ditch network maintenance alternatives and their impacts on water ecosystems. The results of the assessment are utilised in multi-criteria decision support. Impacts of ditch network maintenance on water systems need to be assessed on the basis of expert knowledge, because no quantitative impact assessment models applicable in numerical decision analyses are available. Ideally, the assessment process results in a compromise between the opinions of several experts involved. If no consensus can be reached, the final results are calculated as weighted means of the opinions. For the weighting stage, the competence of the experts should be determined. The method is illustrated and tested in the light of a case study where five experts assessed five ditch network maintenance alternatives with respect to the protection of nearby water ecosystems. The case study area is located in western Finland. It is a peatland site with an old ditch network needing maintenance from the viewpoint of wood production. With the volume increment of the tree stand and the protection of water systems as the criteria, and utilising ecological expertise in the assessment of alternatives concerning the protection criterion, multi-criteria analysis recommended the 'no treatments' alternative.

Key words: AHP, Delphi, ditch network maintenance, environmental protection, forest planning

Abstract: Understorey biomass and species composition were analyzed on six sites representing tall sedge pine fen at different stages of secondary succession caused by drainage for forestry. Two of the sites were undrained controls and the other sites had been drained 8 - 55 years earlier. Cyperaceous and herbaceous field layer was found to diminish permanently after drainage, whereas shrub and moss layers survived in the drainage succession in terms of biomass allocation although the species composition changed almost completely. On the oldest drained site the ground vegetation was dominated by typical upland forest species with the exception of Sphagnum russowii. Total understorey biomass varied from 260 g m^-2 on sites drained 22-30 years earlier to 990 g m^-2 on a site drained 8 years earlier.

Key words: drainage, field layer, ground vegetation, moss layer, peatland, succession

The effect of mineral soil, applied during the cultivation of fields, on the nutrient amounts of afforested peat fields was studied. 36 afforested peat fields (peat layer>40 cm) from Central Ostrobothnia (western Finland) and North Savo (central Finland) were sampled. Fields were divided into two groups on the basis of mineral soil addition. Volumetric soil samples (0-10, 10-20, 20-30, 30-40 cm layers) were taken and and analyzed for their total and ammonium acetate extractable nutrient concentrations (P, K, Ca, Mg, Mn, Fe, Zn). Kjeldahl nitrogen and boron in H₃PO₄-H₂SO₄ were also analyzed. Nutrient amounts in different soil layers were calculated. Mineral soil, mainly silt, had been added on average 230 m³ha^-1 in Central Ostrobothnia and 630 m³ha^-1 in North Savo. Mineral soil was clearly detectable in the plough layer (0-20 cm) but seldom in the 30-40 cm layer as an increased bulk density and ash content. Mineral soil admixture increased most of the total nutrient amounts, but not nitrogen, calcium and boron. In the amounts of extractable nutrients the effect of mineral soil admixture was smaller.

Key words: afforestation, mineral soil, nutrition, peat fields

Abstract: The stand-level responses to fertilization and refertilization were studied in seven factorial field experiments established in 1974-1976. The factors were nitrogen fertilization (N) and phosphorus-potassium fertilization (PK). The factorial treatments were applied at two levels: (i) control and (ii) fertilized with a dosage following the currently used Finnish forest fertilization guide-lines. The spruce-dominated stands were selected from areas drained according to normal forestry practises between 1932 and 1969. The sites covered fairly well the trophic variation that occurs on spruce-dominated peatlands in the mid-boreal zone in Finland. Tree growth was monitored during two periods of five to seven years. The second period followed the refertilization in 1985. At the end of the second period, one-year-old sun-exposed needles were sampled from the four southernmost stands for nutrient analyses. The effects of fertilization on tree growth were generally fairly weak and insignificant, especially during the first study period. After refertilization, the effect of N was positive in three stands on mesotrophic sites. The foliar nutrient analyses of unfertilized spruces showed low concentrations of N, P and Cu. PK-fertilization increased foliar P concentrations and, in some cases, also K concentrations. Since the PK-fertilizer included some borate, it also increased foliar B concentrations. N-fertilization did not affect foliar N, P or K concentrations but it decreased foliar concentrations of Ca, Zn, and B in some cases. Both the growth responses and the foliar nutrient analyses indicated that nitrogen was the most deficient macro-nutrient.

Key words: foliar nutrients, growth responses, mires, nitrogen, phosphorus, Picea abies, potassium

Abstract: The foliar chemical composition of a Norway spruce underwood were analysed one year before and in three years after the removal of a downy birch (Betula pubescens Ehrh.) shelterwood on an old drainage area. The most remarkable change due to the release was considered to be the significant decrease in the potassium concentrations. The nitrogen concentrations increased very strongly, and phosphorus increased slightly but not significantly during the first growth period after the release, decreasing later to a level approaching the deficiency limit. Consequently the nutrient balance between N and K was strongly shaken by the increased N/K-ratio. One reason for that might be the increased use of K in the growing points of roots after the root competition of shelterwood was eliminated.

Key words: foliar analysis, nutrients, peatlands, Picea abies, shelterwood, underwood.

In north-east Estonia the precipitation of calcium-rich strongly alkaline fly ash from thermal power stations has caused significant changes in the local ombrotrophic mires. Sphagnum mosses disappeared from Niinsaare bog during the 1970s in the period of the highest air pollution. Their disappearance was probably caused mainly by the combination of high pH values and an increased concentration of calcium in the bog water. In Niinsaare bog, the present mean pH value of bog water is 5.3 ( 0.6 and the mean calcium concentration 11.6 ( 1.6 mg l-1, compared with 3.7 ( 0.4 and 1.9 ( 0.2 mg l-1 in the uncontaminated Nigula bog respectively. During the last decade, following the reduction of fly ash emission, the Sphagnum mosses started to reappear in Niinsaare bog. Nine Sphagnum patches dominated mainly by S. angustifolium, S. fallax and S. magellanicum were studied from June 1991 to September 1995. During one year, the distance between the centre and edges of these patches increased on an average by 5.1 ( 2.7 cm and the area by 29 ( 21.5 %. This indicates that the degeneration of Sphagna in NE Estonian bogs is not yet irreversible and, by reducing the air pollution in long term, the restoration of Sphagnum carpet is possible.

Key words: atmospheric pollution, degeneration and recurrence of Sphagna, ombrotrophic mire.

Four excavators were studied in site preparation in different excavation difficulty classes (1-3) during the unfrozen period in the central and the northern Ostrobothnia in western Finland. In mounding the mean productivity (per effective hour) of the excavators was 0.17 ha h-1 and in scarification 0.32 ha h-1, respectively. The work quality was acceptable. In mounding and scarification, the mean number of planting positions was about 3600 per hectare. The mean height of the mound was about 28 cm, the mean dimensions of the scarified surface being 330 cm x 75 cm. The operation costs were 268-388 FIM per hour, if the price of the excavator was 400 000-1000 000 FIM.

Key words: excavator, mounding, scarification, work studies.

The structure of peatland forests were compared between different site quality classes, drainage phases, and different forest ownership groups. The comparisons and statistical tests were made in terms of the number of tree species, range of diameter distribution and the estimated number of tree storeys, separately for spruce- and pine-dominated mires. The statistical tests were performed with multivariate analysis of variance and covariance. Tree storeys were estimated with objective rules from the peaks of continuous diameter distribution smoothed by the non-parametric kernel-estimation. The data used from the 8th National Forest Inventory of Finland.

On average the mean values of the chosen stand structure characteristics differed significantly between the site quality classes. The stands had a more diverse structure the more fertile the site was. When examining the differences between the post-drainage succession phases, a decrease of the stand structure diversity was observed in the recently drained peatlands. After this, the mean values of the stand structure characteristics increased and exceeded the values of undrained peatlands at latest in the transformed post-drainage succession stage.
Statistically significant differences in the means of stand structure characteristics between the forest ownership groups were not observed. It seems that drainage and possible cleaning cuttings have been made with the same intensity regardless of the particular forest ownership group. It is also possible that drainage causes so drastic change in growing conditions that small differences in the intensity of cleaning cuttings between forest ownership groups are disappeared.
The results correspond to the results of previous studies which have examined different stand structure characteristics. The forest on drained peatlands maintains an uneven-sized structure for quite a long period after drainage. In order to preserve habitat diversity this structure of the peatland forests should be maintained in subsequent forest management practices.

Key words: drainage, habitat diversity, peatland forest management, structure of forest stand.