Ichio Nioh

Season and soil management affect soil microbial communities estimated using phospholipid fatty acid analysis in a continuous cabbage (Brassica oleracea var. capitata) cropping system

Abstract The effects of soil management on seasonal changes in soil microbial communities were examined in a continuously cropped field of cabbage (Brassica oleracea var. capitata) using phospholipid fatty acid (PLFA) analysis. Soil samples from each plot treated with cattle manure compost (CMC), grass compost (GRC) and chemical fertilizers (CHF) were taken at monthly intervals from April 2003 to March 2004. The results showed that microbial biomass was smaller in the CHF-treated plot than in the other plots. The mole-percentage contributions of biomarkers for Gram-negative bacteria slightly decreased from April to September and increased from September to March in all plots. The mole-percentage contributions of biomarkers for fungi and actinomyces were greater in the CHF-treated plot compared with the other plots. The mole-percentage contributions of biomarkers for Gram-positive bacteria increased in the order of CMC > GRC > CHF. Higher ratios of cyclopropyl fatty acids to their precursors and lower ratios of monounsaturated fatty acids to saturated fatty acids suggested greater stress to bacteria in the CHF-treated plot than in the other plots. Principal component analysis of the PLFA profiles indicated that soil microbial communities exhibited similar shifts in response to seasonal changes irrespective of the treatment.

Nitrogen fixation associated with the leaf litter of Japanese cedar (Cryptomeria Japonica) of various decomposition stages

Abstract Leaf litter and organic layer samples from Japanese cedar (Cryptomeria japonica) forests with varying decomposition stages were tested for nitrogen-fixing (acetylene-reducing) activities. The result obtained with samples from Gifu University Forest in Kuraiyama indicated that nitrogen-fixing activity was found almost exclusively at a certain limited stage of decomposition, possibly a fairly early stage termed F1 fraction. Specific activity for acetylene reduction by the fraction was 11.0 nmols acetylene reduced/g dry matter/hr. The maximum activity was obtained under 10% oxygen in the atmosphere, and this activity was 1.5 times higher than in 20% oxygen concentration. Nitrogen-fixing activity was measured of the litter and organic layer samples from several locations of Brown Forest Soil of various soil types under Japanese cedar forests. Again, the activity was found generally in F1 fraction. The F1 fraction was characterized by higher moisture content and pH, higher rate of carbon dioxide evolu...

Microorganisms in tile forest soils with different vegetation

Abstract Characteristic microfloras have been found to exist corresponding to the soil types. In cultivated soil, corynebacteria have been shown to be one of the dominant groups, and In grassland soil has been characterized by pseudomonads (1–3). In contrast, pine forest soil has been shown to contain Bacillus as a dominant genus (4).

Input and Output Flux of Carbon and Nitrogen in Decomposing Leaf Litter of Japanese Cedar

Abstract In order to analyze the pattern of loss of carbon and nitrogen from decomposing leaf litter of Japanese cedar (Cryptomeria japonica D. Don), the carbon and nitrogen influx and outflow were measured over a period of 60 months. The fresh leaf litter was cut into pieces, put into a plastic pot with an outlet in the lowermost part and set on the forest floor. The rainwater passing through the litter layer was collected every time, and the pH and amount of carbon and nitrogen were measured. An empty pot was set beside the plastic pot and the rainwater (throughfall) was also collected. After the rain passed through the litter layer the pH increased by a maximum of 2.9, presumably due to the leaching of cations such as calcium and magnesium. At the very early stage of the decomposition, the leaching of a relatively large amount of carbon and nitrogen followed by periodical in- and output flux was observed. The measurement of ammonium- and nitrate-N showed that at first these inorganic forms accumulated ...

Some characteristics of nitrogen-fixing bacteria isolated from cultivated and uncultivated sites

Abstract Nitrogen-fixing bacteria grown in semisolid malate agar were isolated from the soils and various plant roots of cultivated and noncultivated sites in and near Tokyo University Forest in Aichi, and characteristics of the isolates were compared. Nitrogen-fixing bacteria were present in all of the root and soil samples from the cultivated site, and most of them were Azospirillum brasilense-like. All of these isolates reduced nitrate and a large portion of them formed gas in anaerobic culture. The incidence of nitrogen-fixing bacteria from the forest site was much lower and their presence was demonstrated in about 40% of the forest samples. The characteristics of the forest isolates were generally different from those of A. brasilense, as they required yeast extract for nitrogen-fixing growth. More than half of the forest isolates failed to reduce nitrate and none of them produced gas from nitrate. Since the characteristics of both types of bacteria in the cultivated and the forest sites were observe...

Characteristics of bacteria in the forest soils under natural vegetation

Abstract Characteristics of the predominant bacteria isolated in November and May from the forest soils of both dry and wet types under natural vegetation were studied. Although Gram-negative rods were the most abundant bacteria in both soil types and in both seasons, their contents were less and other bacteria especially spore-forming ones increased in May. Among Gram-negative rods in the soil of the dry type in November, the most predominant was those with nonchromogenic rods motile with polar flagella which grew in a simple synthetic media containing glucose or p-hydroxybenzoate and ammonium as the sole carbon and nitrogen sources. In May, the ratio of the bacteria which require amino nitrogen or those with more chomplex nutritional requirement increased. In the soil of moderately wet type, the difference in kinds of bacteria between the two seasons was not so clear as that in the dry type. Most of Bacillus species obtained in these soils were those requiring amino acids or other growth factors among w...