Seasonal change in N<Subscript>2</Subscript>O flux from forest soils in a forest catchment in Japan

Temperate forest soils are one source of nitrous oxide (N₂O), which is an important greenhouse gas and the most important ozone-depleting substance. To clarify N₂O flux mechanisms in relation to soil temperature, moisture, and nitrification activity, we measured N₂O fluxes and net nitrification rates over 3 years at the lower (Japanese cedar) and upper (deciduous broad-leaved trees) parts of a hill slope in a small forest catchment in the northern Kanto region of Japan. The N₂O flux was measured by the closed-chamber technique every month, along with soil temperature and water-filled pore space (WFPS). At the lower slope, the N₂O flux increased with increasing soil temperature (r ² = 0.383, P < 0.01) owing to an increase in the nitrification rate. At the upper slope, no positive linear correlation of N₂O flux with soil temperature, WFPS, or nitrification rate was observed. The low N₂O flux at the upper slope during summer was caused by the low summertime WFPS there. We attributed the higher mean N₂O fluxes observed at the lower slope (median 2.36 μg N m⁻² h⁻¹) than at the upper slope (median 1.10 μg N m⁻² h⁻¹) to a high soil moisture during summer season in the surface soil of the lower slope.     

Investigation into the durability of washed rice straw for equine bedding and the repetitive use of washing water

The present experiment investigated durability during the repetitive use of washed rice straw, as bedding material, and washing water as a model study. Residual nitrogen levels, elasticity, and water suction rates for washed rice straw‐adhered urea were measured. In addition, outflow levels of nitrogen and mineral ions (Na⁺, NO₂^‐ + NO₃^‐, SO₄^2?, PO₄^3?, Cl^‐) for washing water were measured to determine durability. Nitrogen levels of rice straw significantly (P < 0.05) decreased after two washings. There was no significant change in elasticity of repetitively used rice straw. Suction rates of rice straw after the second and third washings increased significantly (P < 0.05) compared to the first time. With regard to the number of washings, the mineral ion outflow level in the washing water for nitrogen, Na⁺, NO₂^‐ + NO₃^‐ and PO₄^3? after each washing was not significant. However, nitrogen outflow level tended to decrease after the third washing. SO₄^‐ and Cl^‐ did significantly decrease (P < 0.05) with the number of washings. In this study, it was considered that rice straw and washing water could be used repetitively three times. Furthermore, in order to maintain effluent standards, washing water from the first washing needs to be processed in a septic tank.     

Increase of ruminal fiber digestion by cellobiose and a twin strain of Saccharomyces cerevisiae live cells in vitro

This experiment was designed to investigate the effects of different concentrations of cellobiose (CB) or a twin strain of Saccharomyces cerevisiae live cells (YST) (20, 40 and 60 mg/60 mL), and CB + YST (60 + 20, 60 + 40, 60 + 60 mg/60 mL) on mixed ruminal microorganism fermentation in vitro. Ruminal fluid was collected from a cow, mixed with phosphate buffer (1:2) and incubated (60 mL) anaerobically at 38°C for 24 h with or without supplement plus 400 mg (dry matter [DM] basis) substrate (hay plus concentrate, 1.5:1). The medium pH numerically decreased with CB and CB + YST, but was unchanged with YST. The total volatile fatty acid and proportion of propionate increased (P < 0.05) in all cases. The proportion of acetate decreased (P < 0.05) with CB and CB + YST, but increased (P < 0.05) with YST and that of butyrate increased (P < 0.05) with CB and CB + YST, but decreased (P < 0.05) with YST. Ammonia‐N decreased (P < 0.05) with CB and CB + YST, but was unchanged with YST. The number of protozoa was unchanged, and that of cellulolytic bacteria increased (P < 0.05) in all cases. Total gas production increased (P < 0.05) in all cases. Methane decreased, hydrogen was unchanged by YST and both gases were unchanged by CB and CB + YST. The in vitro disappearance of DM and neutral detergent fiber increased (P < 0.05) by 11.2% and 8.9%, 9% and 8.5%, and 12.1% and 10.2% in the case of CB, YST and CB + YST, respectively. Therefore, the dietary supplementation of CB and/or YST may improve ruminal fermentation and digestibility.     

Effects of cecectomy on digestion and retention time of digesta in rats

The present experiment aimed to obtain basic knowledge of the role of the cecum in the digestion of protein, fiber and energy, and in the retention of digesta in rats. Twelve healthy male Sprague–Dawley strain rats were used. The experiment lasted for 8 weeks following preliminary feeding. Crude protein [CP], acid detergent fiber [ADF], and energy digestibilities were measured in weeks 1, 4, and 7 of the experiment, while the digesta retention time was measured in weeks 2, 5, and 8. At the end of the test, the colon capacity was measured after killing the rats with diethyl ether. The effects of the cecectomy were not recognized in bodyweight gain, even while the feed intake was high and the feed efficiency was low due to the cecectomy. However these effects were not recognized in the latter half of the test periods. The mean retention time of digesta for the cecectomized rats was about 2 h shorter than that for the control group of rats, while the retention time of digesta in week 8 increased compared to weeks 2 and 5. The digestibility of each substance was significantly lower following the cecectomy. The colon became swollen because of the cecectomy and this swollen colon made up for the capacity of the dissected cecum. It had been considered that the cecum does not play a role in the digestion of nutrition for growth, however, the present results showed two types of effects of cecectomy: one that disappears in accordance with time after surgery (i.e. feed intake and feed efficiency), and another that continues for a longer period (i.e. digestibility, retention time of digesta).     

Analysis of yield attributes and crop physiological traits of Liangyoupeijiu,a hybrid rice recently bred in China

Crop physiological traits of Liangyoupeijiu, a “super” hybrid rice variety recently bred in China, were compared with those of Takanari and Nipponbare in 2003 and 2004 in Kyoto, Japan. Liangyoupeijiu showed a significantly higher grain yield than Nipponbare in both years, and achieved a grain yield of 11.8 t ha⁻¹ in 2004, which is the highest yield observed under environmental conditions in Kyoto. Liangyoupeijiu had longer growth duration and larger leaf area duration (LAD) before heading, causing larger biomass accumulation before heading than the other two varieties. Liangyoupeijiu had a large number of grains and translocated a large amount of carbohydrates from the vegetative organ to the panicle during the grain filling period. The three yield components measured were panicle weight at heading (P₀), the amount of carbohydrates translocated from the leaf and stem to the panicle during the grain filling period (ΔT), and the newly assimilated carbohydrates during grain filling (ΔW). It was found that the sum of P₀ and ΔT were strongly correlated with grain yield when all the data (n = 8) were combined (r = 0.876**). However, there was no significant difference in the radiation use efficiency (RUE) of the whole growth period between Liangyoupeijiu and Nipponbare for both years. Even though the growth duration was shorter, Takanari, an indica/japonica cross-bred variety, showed a similar yield to Liangyoupeijiu in both years. The mean RUE of the whole growth period was significantly higher in Takanari, 1.60 and 1.64 g MJ⁻¹ in 2003 and 2004, respectively, than in Liangyoupeijiu, which had a RUE of 1.46 and 1.52 g MJ⁻¹ in 2003 and 2004, respectively. The high grain yield of Takanari was mainly due to its high RUE compared with Liangyoupeijiu and its large P₀ and ΔT. Our result showed that the high grain yield of Liangyoupeijiu was due to its large biomass accumulation before heading, which resulted from its large LAD rather than its RUE.     

Groundwater flow and transport and potential sources of groundwater nitrates in the Ryukyu Limestone as a mixed flow aquifer in Okinawa Island, Japan

We investigated the groundwater flow and the transport and potential source of groundwater nitrates in the typical karst setting of the Ryukyu Limestone aquifer in the southern part of Okinawa Island, Japan. Analysis of groundwater hydrographs indicated that this is a ??mixed flow?? aquifer with the coexistence of slow diffuse flow in the matrices and rapid conduit flow in the caves and caverns. This relationship is indicated by the travel time of groundwater flow: 70?days in the matrices of the aquifer and 6?days through the caves and caverns. The conduit flow system was also confirmed by the distribution of relatively low concentrations of ²²²Rn near caverns. The sampling sites were categorized into upland field (UF) type and residential area (RA) type according to the land-use ratio on the upstream side with a 600-m influential radius, and cave and cavern (CC) type according to the hydrogeologic setting near two large caverns, even though the CC type should be categorized as the UF type from the viewpoint of land use. Cross plots of NO₃-N versus SO₄ ^2? showed that the predominant source of UF groundwater nitrates was chemical fertilizer. A difference was observed in average ??¹⁵N values between UF (8.9??) and RA (10.0??). On the other hand, the average ??¹⁵N value for CC (10.5??) was similar to that for RA, indicating that CC nitrates were not related to the surrounding land use. This phenomenon is considered as evidence that CC groundwater nitrates were carried by rapid groundwater flow through caves and caverns from residential areas located higher upstream compared to the influential areas. According to previous studies, animal and human waste was considered the predominant sources of RA and CC groundwater nitrogen. The contribution ratio of chemical fertilizer (R _CF) was calculated using mass balance equations under assumed predictability. There was a relatively high correlation between the rate of upland areas and of residential areas and R _CF. Average R _CF for UF, RA and CC was 41, 27, and 25%, respectively.     

Identification of Renieramycin A as an Antileishmanial Substance in a Marine Sponge Neopetrosia sp.

The newly developed assay system using recombinant Leishmania amazonensis expressing enhanced green fluorescent protein (La/egfp) has been applied to the screening of Japanese marine sponges for antileishmanial activity. Bioassay-guided fractionation of an active sponge Neopetrosia sp. afforded an active compound which was identified as renieramycin A by spectroscopic analysis. It inhibited La/egfp with an IC₅₀ value of 0.2 μg/mL.     

Comparative digestion of cell wall components of alfalfa hay cubes between Sika deer (Cervus nippon) and cattle

Four female Sika deer (mean bodyweight, 48 kg) and three male Holstein cattle (mean bodyweight, 209 kg) were offered alfalfa hay cubes at 2% (deer) and 2.5% (cattle) of bodyweight, respectively. The digestibility of the cell walls and cell wall components (rhamnose, arabinose, xylose, mannose, galactose and glucose) in alfalfa and its retention time of the alfalfa in the digestive tract and rumen parameters were determined. Cell walls and xylose were less digestible in the deer than in the cattle (P < 0.01 and P < 0.05, respectively). The digestibility of galactose in the deer was as high as that in the cattle. The digestibility of the other sugars and total neutral sugars was numerically lower in the deer, but the differences were not significant. In the deer, mannose was most digestible, followed in order by galactose, arabinose, glucose, rhamnose and xylose; whereas, in the cattle, mannose was most digestible, followed in order by arabinose, glucose, galactose, rhamnose and xylose. The retention time in the digestive tract was shorter in the deer than in the cattle. In the deer, the number of ruminal protozoa was somewhat higher, and the concentrations of propionic acid and butyric acid were higher (P < 0.05) than in the cattle. These results indicate that Sika deer might utilize pectic polysaccharides as a carbon source in preference to glucose containing polysaccharides such as cellulose. The lower digestibility of all cell wall components except galactose in the Sika deer might be mainly due to its shorter retention time.     

White root rot disease of the lacquer tree <Emphasis Type="Italic">Toxicodendron vernicifluum</Emphasis> caused by <Emphasis Type="Italic">Rosellinia necatrix</Emphasis>

In early August 2010, lacquer trees (Toxicodendron vernicifluum) severely damaged by a root rot disease were found on plantations in Iwate, Japan. The causal agent was a fungus identified as Rosellinia necatrix, based on morphology and the sequence of the ribosomal DNA internal transcribed spacer region. The fungus was clearly pathogenic on T. vernicifluum root plantings. This report is the first of white root rot on T. vernicifluum.