Current issue: 54(4)
Dilution plate method was used in studying the density and composition of the microfungal populations of the organic layer of Scots pine forests, and the soil-plate method in studying the part of these populations decomposing cellulose. The media used were rose bengal agar (Martin’s medium for fungi) and cellulose medium.
The microfungal density depended to a considerable extent on the moisture content and temperature of the organic layer. Only the combination of relatively high moisture content and temperature, but neither of these factors alone, influenced considerably the microfungal population density. The correlation of the populations to the changes in this combined factor was stronger than the correlation to the seasonal variations of spring, summer and autumn.
The microfungal population consisted of only a few species. Mucor, Mortierella and Penicillium were the most common genera isolated from the rose bengal agar. The first and the last of these comprised almost 90% of the total population. For the Mucor fungi, increases in the moisture content up to the maximum values found (75%) were favourable; the Penicillium fungi, on the contrary, were intolerant of high moisture content.
Among the cellulose decomposing microfungi grown on cellulose medium, Trichoderma sp. was the most common; also, it formed the most colonies, tolerated the lowest temperatures, and was most efficient. The others were of the genera Pullularia, Verticillium, Scopulariopsis and Penicillium. In addition, there were some unidentified Phycomycetes fungi. Only the two first-mentioned caused observable changes in cellulose.
The purpose of this investigation was to obtain a preliminary picture of the composition of the microbial population in some virgin soils on forest land in Finland. Four different forest types were studied, Oxalis-Myrtillus type birch (Betula sp.) stand, Oxalis-Myrtillus type Norway spruce (Picea abies (L.) Karst.) stand, Vaccinium type Scots pine (Pinus sylvestris L.) stand, and drained pine bog. In addition, a flood meadow was selected as a comparison.
The methods used captured only part of the fungi growing in the soil. Rapidly growing types, especially Mucor and Penicillium species, were mainly isolated. In addition, fungi showing activity of decomposition, such as Fusarium, Monosporium and Spicaria, as well as an ascomycete of the genius Ascobolus, were isolated. Autochthonous bacteria were most abundant in the soils of Oxalis-Myrtillus type forests and in the flood meadow. In the birch stand 90% of the autochthonous bacterial flora were gram-negative bacteria, in the Oxallis-Myrtillus spruce and Vaccinium type pine stand 60% were gram-negative, while the share was only 25% in the pine bog. Nitrogen-fixing bacteria of the type Clostridium pasteurianum were found in all soils. Actinomycetes were found in all sites. The numbers of protozoa were highest in the soils of Oxalis-Myrtillus type forests.
There were no big differences between the forest soils and the flood meadow. Some groups of micro-organisms seem to be absent from the forest soils, which is probably due to the more favourable pH in the meadow. The occurrence of myxobacteria is interesting since no earlier data exist of this organism in Finnish soils.
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The aim of the study was to identify the microbes which reach the cut surface of Norway spruce (Picea abies (L.) Karst.) stumps during the first year after felling by means of air born spores, determine their occurrence frequency and the combinations in which they occur, investigate the colour changes in the wood caused by microbes and identify the microbial species isolated from the sap- and heart-wood.
The material consisted of 360 spruce stumps. 300 of the stumps were innoculated with five different fungi (Phlebia gigantea, Botrytis cinerea, Gliocladium deliquescens, Trichoderma viride, Verticicladiella procera) in order to inhibit air-born attack by Heterobasidion annosum. 60 stumps were left untreated as controls.
The cultural characteristics of the following fungi isolated from the stumps have been described e.g.: Ceraceomerulius serpens, Chondrostereum purpureum, Cylindrobasidium evolvens, Peniophora pithya, Phlebia gigantea (Phlebiopsis gigantea) , P. subserialis, Sistotrema brinhmannii, Bjerkandera adusta, Coriolellus serialis, Trametes zonata, Armillariella mellea, Panellus mitis, Nectria fucheliana (microconidial-stage), Ascocoryne cylichnium (conidial-stage), Leptographium lundbergii, Acremonium butyri, Gliocladium deliquescens, Verticicladiella procera.
The proportion of Basidiomycotina fungi out of the whole material was 53 %, Ascomycotina and Deuteromycotina fungi 37,6 % and bacteria 7,3 %.
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Infection of living Norway spruce (Picea abies (L.) H. Karst.) trees by bacteria, and the properties of these bacteria were studied. Bacterial antagonism to three decay fungi was also studied in laboratory conditions.
Bacteria could be found in 26% of all spruce injuries. Bacterial infection was most frequent in injuries made in March–April and June, and least frequent in December–February. Bacteria infected most often sapwood injuries in roots above soil level, 55% of the bacterial colonies were isolated from these injuries. 27% of the colonies were isolated from injuries made by increment borer at breast height, extending to heartwood, 16% from sapwood injuries at breast height, and 2% from injuries at stump height. The main bacterial groups were gram-positive rods (55%) and gram-negative rods (29%).
In 65% of the bacteria the metabolism was fermentative, in 14% slowly fermentative, in 7% oxidative, in 8% slowly oxidative, and in 6% alkalizing. 19% utilized cellulose, 15% in the presence of organic, 3% in the presence of inorganic nitrogen.
One bacterial strain was the only micro-organism growing in the injury a year after the damage, although the injury had been infected with Peniophora gigantea (Phlebiopsis gigantea). In laboratory experiments, this rod bacterium, gram-negative strain proved to be antagonistic to Fomes annosus (Heterobasidion annosum), Stereum sanguinolentum and P. gigantea. It had no capacity for cellulose utilization.
The PDF includes a summary in Finnish.