The aim of this study was to clarify how temperature underlines the proportion of C_3 and C_4 grasses along an alitudinal gradient in the Kirigamine grassland of central Japan. We investigated the altitudinal patterns of C_3 and C_4 plants in the Kirigamine grassland (1,500 to 1,920m a. s. l.), and analyzed its relationship to temperature, topography and soil carbon and nitrogen contents based on field survey data of 1992 to 1995. The C_4-grass percentage (measured as % of total grass coverage or biomass) decreased and the C_3-grass percentage increased with altitude, indicating the existence of a transition between C_3 and C_4 grasses in the grassland. Seasonal changes in the proportion of C_4 and C_3 grasses of the C_3-C_4 transition indicated that there was a shift of productive activities from C_3 to C_4 grasses with increasing temperature. The significant correlation between percentage of C_4 and C_3 grasses and temperature-related factors suggests that temperature is of primary importance in determining the proportions of C_4 and C_3 grasses along the altitudinal gradient. Precipitation, soil C and N contents, and topographical factors (slope inclination and aspect) showed less influence on the transition in the grassland. On the other hand, the C_3-C_4 balance point (C_3 and C_4 grasses each constituting 50% coverage) in the Kirigamine grassland had a mean August (the warmest month) minimum temperature of 13℃, which was in rough agreement with the balance point in other temperate regions but higher than that of tropical regions. This suggests that C_4 plants require warmer summer for distribution to higher latitudes. We measured carbon isotope ratios (δ^<13>C) of vegetation and found that the values decreased with increasing altitude, and indicating the transition from C_4 to C_3 grasses with increasing altitude as well. Moreover, we clarify the changes in altitudinal pattern of C_3 and C_4 plants in past vegetation of the Kirgamine grassland, based on the changes in carbon isotope ratios of present vegetation and soil organic matter with increasing altitude. The δ^<13>C value of soil organic carbon at the 1660-m site was -18.2‰, while the present vegetation δ^<13>C value was -18.6‰, suggesting a similar C_3/C_4 ratio in the past (recorded in soil δ^<13>C value) as at the present at this site. However, at the 1715-m and 1830-m sites, the soil δ^<13>C values were -19.5‰ and -21.2‰, whereas the present vegetation δ^<13>C values were -22.3‰ and -26.1‰, respectively. These results strongly suggest that a greater proportion of C_4 plants occupied the communities at the higher altitudes in the past.

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Between 1974 and 1989, two 8-year-long grazing experiments were conducted at the National Grassland Research Institute (Nishinasuno, Tochigi, Japan) to determine the effects of grazing intensity and nitrogen levels, respectively, on the pasture ecosystem. Large temporal and spatial variations in phytomass were observed in both experiments. To clarify the cause of the phytomass variations, the present study re-examined the data obtained in these two experiments to determine the effects of four factors and their interactions : Year, Season, Plant species and Treatment (two different grazing intensities or two different nitrogen levels). Although these experiments were not based on any statistical experimental design, we were able to examine these factors using analysis of variance for single-replication experiments. In the analyses, Year was treated as a random effect factor, and Season, Plant species and Treatment were treated as fixed effect factors. The 4-factor interaction was assumed as the experimental error. Based on variance-component values calculated from the analysis of variance, the degrees of contribution of main effects, 2- and 3-factor interactions and error to the whole phytomass variation, were numerically calculated. In these two experiments, the effects of Plant species and 2- and 3-factor interactions containing Plant species made the greatest contributions to the phytomass variations.

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Atmospheric carbon dioxide (CO_2) concentration (app. 370μmol mol^<-1>) is predicted to double by the end of this century. The objective of this study was to evaluate the effects of elevated atmospheric CO_2 on forage yields of perennial ryegrass and red clover in Hokkaido. The two species were grown as monocultures in a factorial design of two CO_2 concentrations (ambient and doubled) and two nitrogen (N) fertilizer levels (with and without N) using open top chambers at the Hokkaido University Experimental Farm for two years to examine forage yields and the numbers and sizes of tillers and petioles in monthly cuts. Regardless of N level, the ryegrass yield increased with doubled CO_2 throughout the two years, owing to mutual stimulations of the tiller number and size. The clover yield increased only slightly in the first year, but dramatically in the second year. The slight increases in the first year resulted from the absence of petiole number stimulation. Reflecting the different responses to CO_2, the mean yield increased 43% for ryegrass and 30% for clover. Comparison of these rates with those reported previously suggests that future CO_2 enrichment will elevate forage yields of the two species in Hokkaido to a greater extent than those predicted for other regions.

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In this study, the performance of nine Japanese coolseason grass cultivars representing five species were evaluated in central Oklahoma, USA. Forage production, persistence data and climatological data were obtained to identify the performance of Japanese cool-season forage grasses and their possible use as a breeding resource. Data from the four year study indicate 'Akimidori' orchardgrass, 'Nanryo' tall fescue, 'Harusakae' meadow fescue and 'Shiwasuaoba' Italian ryegrass have value and a capacity for additional breeding improvements for both central Oklahoma and Japan. 'Akimidori' orchardgrass, 'Nanryo' tall fescue and 'Harusakae' meadow fescue each exhibit tolerance to drought and heat stress. As a consequence, these cultivars indicated good persistence in the years evaluated. 'Shiwasuaoba' annual ryegrass, by virtue of its early maturity, escaped periods of drought and heat stress in central Oklahoma and was well suited to no-till forage-grass-vegetable rotations. Multi-year performance testing of Japanese cool-season grasses in the climatic extremes of central Oklahoma provide a useful selection tool for drought and heat tolerant germplasm for both Japanese and American breeding programs.

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We investigated the effects of ammonia treatment under various conditions on the viability of Mycobacterium avium subsp. paratuberculosis (MAP), which contaminates low moisture roughage. A small resin bag called a pouch silo and containing ground alfalfa hay was used as a container for ammonia treatment. The ammonia treatment was performed on a laboratory scale with NH_4 OH and a filter paper infiltrating cultured MAP suspension. At a 3% concentration, except for the 1st day under 10℃ and 20% moisture conditions, no surviving MAP was observed within 3 days after addition of ammonia. When treated with 1 and 2% concentrations of ammonia, MAP was observed to survive under conditions of low temperature and low moisture. The correlation coefficients between viability and material moisture, processing temperature, ammonia concentration, and the number of treatment days were determined to be weak at -0.39, -0.38, -0.34, and -0.26, respectively. The result suggests that hay contaminated with MAP could be disinfected by ammonia treatment under fixedconditions.

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Leguminous Galega (Galega orientalis Lam.) that was introduced from Estonia was investigated in mono and mixed sowing cultivation for the growth characteristics and adaptability in Hokkaido, compared with alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.). Galega developed rhizomes vigorously, and showed elect plant type with high proportion of leaves. The plant height was 100 to 110cm at first and second cut, but it elongated shortly at third cut. The date of flowering at first cut was 7 to 10 days earlier than that of alfalfa, but it showed later flowering at second cut and no flowering at third cut. The seeds were 3.5 to 4.3 times bigger than those of alfalfa and red clover, and the thousand seed weight was 7.8 grams. Percentage of the dry matter weight composition of first cut was very high (58.9%) and that of third cut was very low (6.6%). The forage qualities of fresh materials, namely, CP, ADF and NDF, were more stable in the cours of growth than those of alfalfa. Galega has a good lodging tolerance and any serious leaf disease was not observed. Galega showed good persistency and high adaptability under the mixed cultivation with timothy in Hokkaido.

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Dry matter (DM) and nutrients of edible plant groups were monitored monthly during the grazing season in the national agro-forest consisting of many lots of about 10 ha with various aged Japanese cedars planted and these surrounding broadleaf trees. Plant groups were bamboo, sedges, butterbur, tree leaves, forbs, and vines. Compositions of plant groups were quite different among lots. Average DM was 133 g/m^3 in this forest. There was always enough DM of about 28 times of the DM requirement during the whole grazing period for all grazing cows in the estimated home range. Average crude protein content and crude fiber content were 11.9 and 19.2% in this forest, respectively, which are enough for rearing the beef cow. Although the seasonal change of nutrients was different among lots, it is thought that cows could get balanced nutrition by selective grazing in this forest. Many lots, however, were poor in nutritional condition in October, which suggests affecting on the behaviour of cows.

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Effect of salt stress on fructan concentrations in leaf sheaths of forage grasses was investigated using salt tolerant (perennial ryegrass and Italian ryegrass) and sensitive grasses (tall fescue and meadow fescue). By treatment with NaCl (150 mM), mono- and oligosaccharide concentrations unchanged in the salt tolerant grasses and meadow fescue compared with control, and decreased in tall fescue. The concentrations of fructan increased in the salt tolerant grasses compared with control by the NaCl treatment, while those in the salt sensitive grasses decreased (tall fescue) and unchanged (meadow fescue). The amounts of fructan increased in the salt tolerant grasses compared with control by the NaCl treatment, while those in the salt sensitive grasses decreased. The increase in fructan in salt tolerant grasses was mainly due to the increase in the fraction of high molecular fructan, suggesting that synthesis of high molecular fraction of fructan occurs by the saltstress.

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In a previous report, the authors described a selfpropelled bale wrapper and reported its fundamental structure and performance. This paper reports improvements on the invented self-propelled bale wrapper for advancing its operating efficiency and stabilizing its operation. It also reports a comparison with an invented self-propelled bale wrapper with no improvement. Main improvement items included an upgrade of the engine output from 6.3 kW to 9.6 kW and a change of the film dispenser from the single stretch method to the double stretch method. In addition, we changed fixing positions of an operating section and lift arm from the left side to the right side in the direction of travel. Moreover, we changed the transmission from a mechanical transmission to a hydrostatic transmission. Those improvements increased moving speed in paddy fields and reduced hours required for loading and unloading bales : that time was shortened approximately 5min per 10 a during all work (the number of bales was nine per 10 a). As a result, hours of work were matched with the cutting roll baler for the rice whole crop silage. Thereby, both machines were able to : enter a paddy field at the same time, perform operations from harvesting to baling, perform sealing up activities, and finally carry bales out of the paddy fields continuously, completing the operations almost simultaneously.

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