Small-scale spatial heterogeneity of individual plant species in sown grasslands was investigated using a new experimental and statistical method proposed by SHIYOMI et al. (2000). The frequency of occurrence of each species was used to evaluate the spatial heterogeneity of species distribution. A discrete probability distribution, beta-binomial series (BB) was introduced as a model to describe the heterogeneity. One of the parameters of the BB, p, was used as a heterog.eneity index. The objectives of this study were: (1) to determine whether or not the use of the BB is suitable for describing the spatial distribution of individual species grown in sown grasslands, and (2) to determine how different the spatial heterogeneity is among plant species. It was empirically demonstrated that the BB is a good model to describe the frequency of occurrence of each species population composing sown grasslands. The spatial heterogeneity of the clonal species was significantly higher than that of the non-clonal species. The spatial heterogeneity of the creeping species was significantly higher than that of the erect species. The use of the experimental and statistical method for detecting patchiness of grassland vegetation is suitable for grassland diagnosis.

View full abstract

The influence of spatial autocorrelation on the power of an experimental design to detect the impact of wild burros on the volume of white bursage (Ambrosia dumosa) was studied in the Lake Mead Recreational Area, Nevada, USA. The presence of spatially autocorrelated residuals resulted in both an underestimation and overestimation of treatment means and an underestimation of their respective standard errors. These estimates resulted in an increase in the significance of differences in individual treatments and in the power of the test respectively. A spatial autoregressive model was used to correct for the presence of spatially autocorrelated residuals and used to obtain the best linear unbiased estimates of the parameters. Analysis of covariance showed that volumes per plant decreased significantly with increasing latitude and elevation. Volumes increased significantly with increased distance from the Colorado River. Volumes of individual plants differed significantly among grazing intensity (light, medium and heavy). The explanatory variables used in the covariance model did not account for all the spatial variability in the distribution of volumes.

View full abstract

This study was conducted in order to obtain basic data on managing secondary forests developed on abandoned fields and used for cattle grazing. The area of the experimental site was 1.45 ha. The number of trees in a single 10 m×10 m quadrat set up in the experimental site was 205, and the mean tree height was 2.44m, with broad-leaved evergreen trees (species number=11), broad-leaved deciduous trees (25), and conifers (2) accounting for 49, 46, and 4%, respectively, to the total number of trees. The cattle tracks which developed in the secondary forest formed a complex reticulation. The inclination angle of the cattle tracks ranged from 0 to 29.1 degrees (mean value=8.1 degrees), and 43.9% of the total were less than 6 degrees and 76.6% were less than 12 degrees. The height of Ligustrum japonicum, which was the index tree used to determine the influence of defoliation, increased with the distance from cattle tracks, and this indicated that the degree of defoliation of the wood species by cattle changes with the distance from cattle tracks.

View full abstract

To clarify the heading behavior of the thermo-sensitive sorghum varieties, effects of the timing and duration of the night temperature treatments on the panicle initiation and the final leaf number were examined. Two hybrid cultivars (FS403 and GROWERES30F) and one inbred (932233B) strain were grown in pots under controlled climatic conditions both in low night temperature (LT:15℃) and high night temperature (HT: 30℃). Plants were tramsferred from LT to HT or from HT to LT with several combinations of the timing and duration of temperature treatments. LT induced panicle initiation and reduced final leaf number and HT restrained panicle initiationand increased final leaf number in all varieties. The time when plants first became sensitive to low night temperature was earlier in 932233B than in FS403 and GROWERES30F. The minimum LT duration requiredto induce the panicle initiation (MDPI) was the shortest in 932233B and the longest in GROWERES30F. MDPI was, however, decreased with growth progress in all varieties. The time when plants first became sensitive to high night temperature was the earliest in 932233B and the latest in GROWERES30F.

View full abstract

As part of a study on the heading characteristics of sorghum, the effects of time and duration of the night temperature treatments on the time to panicle initiation and the final leaf number were examined. Thermosensitive inbred strain 932233B were grown in pots under controlled climatic conditions both in low night temperature (LT: 15℃) and high night temperature (HT: 30℃). Plants were transferred from LT to HT or from HT to LT with several combinations of the time and duration of treatment. LT induced panicle initiation and reduced final leaf number and HT restrained panicle initiation and increased final leaf number. However, the degree of the response varied substantially among different treatments. It was suggested that the sensitivity to low temperature was acquired immediately after sowing and the sensitivity to high temperature was acquired at 3-4 leaves stage by the analysis of the above-mentioned response. The minimum LT duration required to induce the panicle differentiation (MLT) decreased with growth until 8 leaves stage, and MLT in number of emerged leaves was negatively correlated with the growth stage in leaf number at the onset of the low night temperature treatment. There were, however, no relationship between MLT and growth stage after 8 leaves stage.

View full abstract

The effect of controlled availability fertilizer (CAF) on the growth and botanical composition of a deteriorated steep grazing pasture which was undergoing frequent cutting was studied. Only the yields of the first cutting in a conventional plot treated by readily available fertilizer (RAF) were 1.4-2.0 times as much as those in a no application plot, however the yields of the later cutting were approximately the same as those in a no application plot. On the contrary, all the cutting yields in the CAF plot were more than 1.2 times as much as those in the no application plot. The annual yields of RAF plot in 1994 and 1995, were 124% and 126% respectively, as compared to those of the no application plot. On the other hand, those of the CAF plot were 141% and 131%, and those of the twofold CAF plot were 154% and 157%, respectively. The yearly mean relative coverage by orchardgrass was only 3% in the no application plot and 8% in the RAF plot, whereas that in the CAF plot was 14% and that in the twofold CAF plot was 23%.

View full abstract

This experiment was carried out to clarify the effects of cellulase (AC), lactic acid bacteria (SL) and wilting on the fermentation quality of reed canarygrass (Phalaris arundinacea L., cv. Venture). Cellulase prepared from Acremonium cellulolyticus Y-94 (AC) was added at ratios of 0.01% and 0.05% of fresh matter, and commercial lactic acid bacteria ((Lactobacillus casei subsp. rhamnosus) inoculant including cellulase (mixture of cellulase derived from a selected strain of Acremonium cellulolyticus and Trichoderma viride)) (SL) was added at a ratio of 0.05% of fresh matter. These were ensiled both with and without the addition of carbon dioxide in order to establish an anaerobic condition at the early phase of fermentation. The effect of wilting was also investigated both with and without the addition of carbon dioxide. These materials were ensiled in experimental silos at a bulk density of 600 kg/m^3. The addition of AC or SL decreased the pH values, but increased the amount of lactic and total acids, the ratio of lactic acid to total acid content, and Flieg's score of silages. The addition of AC or SL decreased the amount of propionic, butyric and vareric acids. There was no statistically significant difference concerning the ratio of volatile basic nitrogen (VBN) to total nitrogen. From these results, it is suggested that the addition of AC or SL can be helpful to improve the fermentation quality of reed canarygrass silages. However, wilting or the addition of carbon dioxide was not effective in improving the fermentation quality.

View full abstract

In this experiment, I investigated the effects of combinations of nitrogen fertilizer and temperature on the early growth of alfalfa under long-day conditions, using ^<15>N-labeled nitrogen. At 20/15℃, there was no difference between the NO_3 plot and NH_4 plot with respect to dry weight, total nitrogen content, and ^<15>N content. At 30/25℃, by contrast, values for all these three variables in the NH_4 plot were higher than those in the NO_3 plot. The relative specific activity (RSA) of ^<15>N in roots at 20/15℃ was comparable in the NO_3 plot and NH_4 plot. At 30/25℃, however, the RSA of ^<15>N in roots in the NH_4 plot was higher than that in the NO_3 plot. These results suggest that differences in the uptake of nitrogen fertilizer, or variations in the distribution of nitrogen to the roots may be responsible for the difference in the effects of NO_3 and NH_4 on the growth at 20/15 and 30/25℃.

View full abstract

Two experiments were conducted to investigate the importance of mineral availability in screening orchardgrass plants for Mg concentration. Mineral availability was evaluated by nylon-bag method using three mature wethers. Magnesium, Ca, K and P were analyzed for original forage samples and residues after 6 digestion times, and disappearance rate of minerals in the rumen were measured. In Experiment 1, mineral availability was investigated with advancing maturity of orchardgrass. Composition of Mg, Ca, K and P declined, and degradability of dry matter also declined. Regrowths, however, did not change in both mineral compositions and degradability. Maximum disappearance rate of Mg, Ca and P decreased with advancing maturity of the first growth. In Experiment 2, mineral availability of orchardgrass was compared with those of tall fescue and reed canarygrass under four hay cuttings per year. Maximum disappearance rate of Mg, Ca, K and P were higher than 90% over three species and four cuttings. There was no significant difference in mineral availability among species. These facts show mineral availability was affected mainly by heading, and the mineral availability may not be so important in screening orchardgrass plants for Mg composition from the population with almost same heading stage.

View full abstract

The objective of this study was to elucidate, that the mechanism of growth depression of red clover by fertilizing with cattle slurry. We investigated the growth response of red clover and nitrogen budget. Continuous fertilizing with cattle slurry clearly decreased the number of shoots, the thickening growth of the main root of red clover, and nitrogen supply by nitrogen fixation during June and August of 1998, two years after sowing. This was attributed to the following mechanisms. 1. The accumulation of organic matter by continuous fertilizing with cattle slurry enhanced nitrogen mineralization. 2. During June and August, temperature exceeded 20℃, and this accelerated nitrification. As a consequence, NO_3-N concentration in the soil increased enough to depress nitrogen fixation. 3. Depression of nitrogen fixation inhibited nitrogen uptake of red clover, decreasing the number of shoots and the thickening growth of the main root.

View full abstract

Effects of an applied nitrogen form on the nitrogen uptake by grasses, undergoing frequent cutting in grazing pasture was studied with ^<15>N-labeled fertilizer. Applied ammonium sulfate (AS)-nitrogen was absorbed by grass just after the application and this resulted in a high yield at the first cutting. On the contrary, applied controlled availability fertilizer (CAF) nitrogen was absorbed by grass mainly grown in the summer and autumn, and resulted in a yearly stable yield. The recovery rates for AS nitrogen applied in the spring in 1995 and in 1996 were 48% and 57% respectively whereas the nitrogen applied in the autumn in 1996 was 51%. On the other hand, recovery rates for CAF nitrogen applied in 1995 and in 1996 were 41% and 47%, respectively, and those in the two fold CAF plot were 41% and 29%.

View full abstract