中国南部天然常绿阔叶林的地上生物量、净初级生产力、养分分布和养分利用效率

在中国南部的江西九连山自然保护区,观测研究了天然常绿阔叶林的地上生物量、地上NPP(净初级生产力)、养分的积累和分布,以及不同生活型树种的养分利用效率.在两个样地,用相对生长回归法和收获法测定了地上生物量,数值各约为340和270t/hm2,其中叶生物量约为9.6t/hm2.地上NPP约为年9.9t/hm2,其中叶生产力占44％.各种一般养分(N,P,K,Ca,Mg,Na)在森林生态系统中积累的特点是,Na和N在矿质土壤中有高的相对分布,K和Mg属中间地位,Ca和P则高分布于地上生物量中.氮的养分利用效率(NUE)、平均停留时间(MRT)和年生产力(A)表明,针叶树是氮的最高效的利用者,常绿阔叶树次之,落叶树在氮的利用上是最低效的.     

人类活动对中国南部荒山松林养分循环的影响

在中国南部开展对荒山马尾松(Pinus massoniana)林养分循环受人类活动影响的调查.位于江西省兴国县研究地点的一些农民从森林生态系统中收取有机物作为燃料,这引起养分循环的断裂和植被恢复的延误以及土壤侵蚀的发生.收取的量估算为相当于5.92t/hm2有机物和21.4kg/hm2氮.如果收取停止,10年之后,有机物在森林地表枯枝落叶层的积累将可恢复.     

Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) in Water Environment of Singapore

Recently, there has been increasing concern about perfluorinated compounds, especially perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) due to their biotic and abiotic persistence and chronic toxicity. To characterize the spatial distribution and seasonal variation of PFOS and PFOA in the aquatic and oceanic environment of Singapore, more than 100 water samples from reservoirs, rivers/canals, coastal waters, and treated effluents of wastewater treatment plants (WWTPs) were collected and analyzed in this study. Solid-phase extraction followed by high-performance liquid chromatography (HPLC) coupled with tandem MS (HPLC/MS/MS) was applied to quantitatively identify PFOS and PFOA. PFOS concentrations in surface waters, wastewaters and coastal waters were in the range of 2.2?C87.3 ng/L, 5.8?C532 ng/L, and 1.9?C8.9 ng/L, respectively, while those of PFOA were 5.7?C91.5 ng/L, 7.9?C1,060 ng/L, 2.4?C17.8 ng/L, respectively. Compared with surface waters and wastewaters, coastal waters had lower concentrations of PFOS and PFOA. Highest concentration of PFOA (532 ng/L) and PFOA (1,060 ng/L) were observed in treated effluents of two WWTPs. Our results suggest that coastal waters in the western area of Singapore are more heavily contaminated than those in the middle and eastern areas. The release of effluents from WWTPs is an important pathway by which perfluorinated compounds enter the oceanic environment. Between dry season and wet season, significant seasonal differences (p?=?0.025) were observed in surface waters for PFOS only, while no discernable seasonal differences were found for both PFOS and PFOA in coastal waters and wastewaters.     

Broth from canned clams is suitable for use as an excellent source of free vitamin B12

Vitamin B(12) was assayed and characterized in the broth of canned clams (boiled plain). The broth contained considerable amounts of vitamin B(12) (2.7-14.1 μg/100 g, 1.3-6.7 μg/can). HPLC and LC/ESI-MS/MS chromatograms demonstrated that the clam broth contained true vitamin B(12). Gel filtration experiments indicated that most (72%) of the vitamin B(12) found in the broth was recovered in free vitamin B(12) fractions. These results indicate that the clam broth would be suitable for use an excellent source of free vitamin B(12) for elderly persons with food-bound vitamin B(12) malabsorption.     

Endogenous 5-HT outflow from chicken aorta by 5-HT uptake inhibitors and amphetamine derivatives

Chemoreceptor cells aggregating in clusters in the chicken thoracic aortacontain 5-hydroxytryptamine (5-HT) and have voltage-dependent ion channels and nicotinicacetylcholine receptors, which are characteristics typically associated with neurons. Theaim of the present study was to investigate the effects of 5-HT uptake inhibitors,fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives,p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HToutflow from the isolated chick thoracic aorta in vitro. 5-HT wasmeasured by using a HPLC system with electrochemical detection. The amphetaminederivatives and 5-HT uptake inhibitors caused concentration-dependent increases inendogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflowthan MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCAand CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HTinduced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca²⁺concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on theextracellular NaCl concentration. These results suggest that the 5-HT uptake system of5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristicssimilar to those of 5-HT-containing neurons in the mammalian central nervous system(CNS).     

Ratio of rice reflectance for estimating leaf blast severity with a multispectral radiometer

 Rice reflectance was measured to determine the spectral regions most sensitive to leaf blast infection with a multispectral radiometer. As disease severity increased, reflectance also increased in the 400–500 nm (blue), 570–700 nm (red), and 900–2000 nm regions but decreased in the 500–570 nm and 700–900 nm regions. The increased reflectance in the blue and red regions may be attributed to decreased chlorophyll and carotenoid contents in response to the blast infection. The maximum and minimum reflectance differences occurred at 680 nm and 760 nm for the nondiseased and diseased rice, respectively. The spectral location of maximum sensitivity was 675 nm regardless of disease severity. Rice reflectance ratios were evaluated as indicators of leaf blast severity. Two ratios, R550/R675 (reflectance at 550 nm divided by reflectance at 675 nm), and R570/R675 quantified the significant disease severity. These wavelengths were selected based on the sensitivity minima and maxima. The ratios of nondiseased rice plants varied depending on growth stage. The variation in ratios must be considered when they are used to estimate leaf blast severity. Received: April 2, 2002 / Accepted: August 12, 2002     

DNA sequence analysis of ribosomal ITS region 1 of Phytophthora vignae f. sp. adzukicola, the pathogen that causes stem rot of adzuki bean

Sequences of the internal transcribed spacer (ITS) region 1 were used to examine the phylogenetic relationships among races of 19 isolates of Phytophthora vignae f. sp. adzukicola and between this forma specialis and three isolates of the closely related P. vignae f. sp. vignae. The ITS 1 sequences were highly conserved (> 98.7% similarity) among representatives of both formae speciales groups. The results of this study indicate that P. vignae is a monophyletic group. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession nos. AB120062–AB120080 and AB120122     

Analysis of Temporal Changes in Botanical Composition of a Long-term Grazing Experiment in Nixinasuno, Japan

In order to understand the temporal changes of botanical composition in grassland ecosystem, and to clarify the relation between these changes and environmental impacts, such as climatic factors and artificial disturbance, a grazing trail was carried out during a 21-year period from 1974 at a sown grassland of the National Grassland Research Institute, located in Nishinasuno, the central area of Japan. The data sets of biomass for each mouth(from April to November)of the 21-year period were analyzed in this paper. The botanical composition of aboveground biomass varied greatly with both season and year. The biomass ratio of improved herbage species to invaded native plants gradually decreased each year. This may have been owing to meteorological factors, such as low air-temperature in winter, dry and hot summers, grassland management(including grazing intensity and fertilizer application), and inter-specific competition between native and introduced herbage plants.     

Methods for determining the consistency limits and constants of soil

The physical analysis of soil tilth has long been one of the important problems in relationship to the solution of soil productivity. Various methods have been proposed to measure soil tilth and most of them are based upon granulation, porosity, penetration and compressibility of soils. In our laboratory here studies³,⁴⁾ for the physical improvement of soil are being continued to find a suitable method of reclamation for heavy clayey polder soils of extremely bad structure in Kojima Bay. In this paper several methods for measuring the consistency limits, and consistency of dry and wet soil are reported, and the value of these methods as a measure of soil tilth is discussed.