Current issue: 57(2)
Under compilation: 57(3)
The purpose of this study was to compare the development of Scots pine (Pinus sylvestris L.) seedlings sown on substrates off milled peat and milled bark. Mille peat, ordinary milled bark, milled inner bark waste, and a mixture of milled peat and milled bark in the ratio of 1:1, were all compared in the plastic greenhouse. In addition, two fertilization applications were used with milled park: ordinary surface fertilization and double surface fertilization. The germination and development were measured twice during the summer.
It is concluded that milled bark seems to be a rather useful substrate for use in plastic greenhouses, as long as its special requirements are taken into consideration. In the first measurement, there were no differences between the treatments, in the second measurements seedlings growing on a mixture of peat and bark were slightly more developed than the others. Growth of the seedlings was slightly better in ordinary milled bark. Double surface fertilization increased disease and mortality compared to ordinary fertilization.
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During the summer and fall of 1966 changes brought about by urea, calcium ammonium nitrate, nitrate of lime, and ammonium sulphate were observed. Application of the fertilizers corresponded to 100 kg/N per hectare.
The effect of urea was immediate. The pH rose and the bacterial density increased to 20–30 times more than determined in the spring, while the microfungal density decreased to one third of the spring density. In the ammonium sulphate plot opposite changes occurred almost as rapidly as in the previous case. A gradually increasing biological activity observed after application of calcium ammonium nitrate and of lime fertilizers seemed almost the same for bacteria and microfungi. Both microbe groups displayed consistent quantitative growth. pH 4.3 was the limit of acidity below which the bacteria showed a tendency to decline and the microfungi to increase, while the opposite was true above this limit.
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This study elucidates the composition of the microfungal populations of the humus layer of tree forest types – Vaccinium type with Scots pine (Pinus sylvestris L.), Myrtillus type with Norway spruce (Picea abies (L.) H. Karst.) and Oxalis-Myrtillus type with birch (Betula sp.). The results indicate that the microfungi encountered in these sites bear close resemblances. The number of species increased but little towards the more fertile sites from VT to OMT. The main difference was limited to the quantitative relationships between the species.
The microfungal density in the humus layer was greatest in VT, and only slightly less in MT and OMT, in this order. In all the sampling areas, occurrence of the microfungi reached a maximum in the middle of summer, at a time when the maximum temperatures were registered in the humus. The quantitative abundance during the early autumn bears a relation to the yield of litter.
The microfungi most commonly encountered in all sampling areas were those of rapid growth, Mucor, Morierella and Penicillium species, along with Trichoderma, a little slower in growth, and actively decomposing cellulose. Mucor fungi, favouring moisture, were most abundant in the early summer and in the autumn. The Mortierella and Penicillium species, which survive dryness, were most abundant in the middle of the summer. The former is twice as common in MT and OMT than in VT, and the latter twice as common in VT as in OMT.
Scopulariopsis and Verticillium species were found regularly in MT and OMT. One Acremonium species was found almost exclusively in VT, and some Aspergillus and Mycogene in OMT alone. Sterilia mycelia was relatively abundant in MT and OMT in particular. Different kinds of yeast fungi were encountered generally in MT and OMT.
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Quantitative investigation of bacteria in the humus is needed when the intensity of their function in decomposition in the soil is studied. In this study bacterial density of humus was measured using dilution plate method, which was subjected to thorough investigation. The method was chosen, despite its complexity, because it is quite consistent, each stage can be studied separately and the reliability can be tested. The aim of the study was to determine the best way to take samples so that the sample will represent the bacterial population as closely as possible, and to optimize homogenization and dilution of the sample and the assays.
On the basis of the results of the investigation, a procedure was developed for quantitative determination of aerobic bacteria in the humus by the dilution plate method. The paper recommends that subsamples are collected systematically from at least 25 different points. The moisture and temperature of the samples should remain similar to the natural environment until preparation of the dilution. The sample was homogenized with the Bühler homogenizer, which is constructed so that a certain degree of asepsis can be maintained and the speed of the apparatus can be regulated. The content of the mineral nutrients of the sample must be determined when choosing the way of homogenization to obtain the highest number of colonies per plate. The sample was diluted with either 0.1–0.01% peptone solution or 0.5% soil extract. The most advantageous degree of dilution was obtained by testing with the aid of Fisher’s dispersion index the probability of the Poisson distribution in the results.
The article deals with laboratory experiments of humus containing soil samples that were tested for leaching of iron and lime. The humus and soil samples were collected in five different areas in Silesian state forests, Germany.
The chemical content of the extracts was measured in the beginning of the test. The flocculation experiments and experiments in glass tubes took place. The stronger or weaker the podsolization, the greater or smaller was the protective action of hums at the respective place. However, more research is needed. The results of the glass tube experiments seem to indicate that with humus there were smaller amounts of Ca and Fe leaching than with merely water.
The vegetation and number of physical and chemical soil properties were studied on a random sample of closed upland forest stands in Southern Finland. The material consists of a total of 410 sample plots. Two-way indicator species analysis (TWINSPAN) was carried out in order to produce a hierarchical clustering of samples on the basis of the vegetation data. Discriminant analysis and analysis of variance were applied in order to find environmental correlations of the vegetation clustering.
The vegetation was found to indicate the nutrient regime of the humus layer well, but to a less extent the properties of the sub-soil. The understorey vegetation was found to be jointly dependent on the site fertility and on the properties of the tree stand, especially on the tree species composition. Although the forest vegetation appears to be distributed rather continuously along an axis of increasing site fertility, relatively unambiguous classification can be based on the appearance of indicator species and species groups.
The results of the study were interpreted as indication that operational site classification done using the vegetation is rather good method for classification in closed forest stands. Different methods produce relatively consistent, natural and ecologically interpretable classifications. The results also imply that the vegetation cover and the humus layer develop concurrently during the development of the ecosystem, but the differentiation of the site type is regulated simultaneously by a number of interacting factors ranging from mineralogical properties of the parent material to the topographical exposition of the site. As the plant cover depicts all these primary factors simultaneously, only a relatively rough ecological site classification can be based on the vegetation.
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Carbon sequestration rates in forest soil can be estimated using the concept of calculable stable remains in decomposing litter. In a case study of Swedish forest land we estimated C-sequestration rates for the two dominant tree species in the forest floor on top of the mineral soil. Carbon sequestration rates were upscaled to the forested land of Sweden with 23 x 106 ha with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (Karst.) L.). Two different theoretical approaches, based on limit-value for litter decomposition and N-balance for vegetation and SOM gave rates of the same magnitude. For the upscaling, using these methods, 17 000 grids of 5 x 5 km were used.
The ‘limit-value approach’ gave a sequestration of 4.8 106 tons of C, annually sequestered in the forest floor, with an average of 180 kg C ha–1 yr–1 and a range from 40 to 410 kg C ha–1 yr–1. The ‘N-balance approach’ gave an average value of c. 96 kg ha–1 yr–1 and a range from –60 to 360 kg ha–1 yr–1. A method based on direct measurements of changes in humus depth over 40 years, combined with C analyses gave an average rate that was not very different from the calculated rates, viz. c. 180 kg ha–1 yr–1 and a range from –20 to 730 kg ha–1 yr–1. These values agree with forest floor C sequestration rate based on e.g. sampling of chronsequences but differ from CO2 balance measurements.
The three approaches showed different patterns over the country and regions with high and low carbon sequestration rates that were not always directly related to climate.
Physical soil properties have a marked influence on the quality of forest sites and on the preconditions for forest growth and management. In this study, water retention characteristics (WRC) and related physical soil properties in addition to vegetation coverage and tree stand data were studied at upland forest sites in Finland. Fixed and mixed models between soil and site characteristics were formed to estimate physical and hydrologic soil characteristics and the site quality with indirect co-varying variables. In the present data, the site quality index (H100) shows a high coefficient of determination in respect to the temperature sum. It is also related to soil fine fraction content, topsoil pH and water retention at field capacity. The thickness of the humus layer is predictable from the pH and cover of xeric and mesic plant species. The soil fine fraction content (clay + silt) is closely related to water retention at field capacity, the soil layer and site type, and without WRC to the temperature sum and site index and type, as well as the slope angle. The soil bulk density is related to organic matter, depth (layer) or alternatively to organic matter, slope and field estimated textural class (fine, medium, coarse). Water retention characteristics were found to be best determinable by the fine fraction content, depth and bulk density. Water content and air-filled porosity at field capacity are closely related to the fine fraction. This study provides novel models for further investigations that aim at improved prediction models for forest growth, hydrology and trafficability.