宁夏沙坡头人工植被区土壤真菌种群的动态研究(英文)

[Objective] The changes of fungi in different soil layers and sand dunes of artificial vegetation areas in Ningxia Shapotou during different times were studied. [Method]The number of soil fungi in different soil layers at same plot and in same soil layer at different plots were changed significantly.The quantitative distribution of fungi was the most in Cuiliugou but the fewest in quicksand among all soil types.[Result] The quantity of soil fungi in grasslands was varied in different soil layers at the same sample and in the same soil layer at different sample plots. The quantity of fungi from different soil types distributed mostly in Cuiliugou, a natural desert steppe, but little in quicksand. The species and quantity of fungi in CuiLiugou was the most in different types of sand-fixing lands. [Conclusion] The quantity of soil fungi in artificial vegetation areas raises with the increase of sand-fixing ages, The enhancement of vegetation construction and artificial management measures in inland is helpful for improving present situation of desertification.     

Plant Diversity and Vegetation Structure in Encroached and Non-encroached Areas of Borana Rangelands： The Case of Hallona and Medhacho Pastoralist Associations

The Borana rangelands are important areas of cattle production in Ethiopia. However, these rangelands are threatened by the increasing changes in the natural vegetation from grass and forbs dominated into unpalatable bushy woody vegetation resulting in the loss of some of the highly desirable grass species. This study was conducted to assess the impacts of bush encroachment on the biodiversity, structure and cover of the native vegetation in bush encroached and non-encroached sites. Vegetation data were collected from both sites by laying quadrate plots along transects using a systematic sampling method. According to the results, higher number of species was recorded in the non-encroached sites than that in the encroached sites. The diversity indices for the non-encroached and the encroached sites were 3.16 and 2.67, respectively. The abundance and cover analysis indicated that there was high density and cover of herbaceous species in the non-encroached site. There was a significantly higher density of woody species cover in the encroached site. Generally, the bush encroachment in the Borana rangelands has hampered the diversity of the native vegetation, particularly the grasses and forbs and reduced the ground cover, exposing large parts of the rangelands for soil erosion and other degradation process.     

The Ecological Effects of Young Elm Trees Belt-Pumpkin Strip Intercropping System at the Agro-Pastoral Ecotone in Northern China

Young elm trees belt-pumpkin strip intercropping was studied to solve the actual problem of resource losses in the large barren area resulted from reconverting cultivated land into forest in the agro-pastoral ecotone in northern China. The final objective was to realize effective utilization of the barren land with both ecological improvement and economic development. Field experiments were conducted together with laboratory analysis. The results indicated that the soil moisture level was remarkably increased in young elm trees belt-pumpkin strip intereropping because the pumpkin vines covered the gap between pumpkin planting-furrow and elm trees belt. The water use efficiency of the intercropping system was increased by 23.7-163.3% as compared with the single cropping. Elm trees belt-pumpkin strip intercropping changed the sequential succession trend of the grasses growing in the gap of the pumpkin planting-furrow. The annual grasses become the dominant vegetation. The nutritive value as fodder and yield of the annual grasses were also increased remarkably. The biomass of pumpkin, elm trees and grasses under intercropping increased by 24.4, 28.4 and 144.4%, respectively, as compared with those under single cropping. The land use efficiency was increased by 132%. It was also indicated that the soil erosion from the intercropping land was not increased due to pumpkin plantation. The differences in the soil erosion among intercropped area, elm trees belt and pumpkin strip with single cropping were not remarkable. Therefore, it was concluded that young elm trees belt-pumpkin strip intercropping is an effective way to utilize the barren land between the young elm trees belt and realize synergistic enhancement of ecological benefit and economic profit.     

Constructing a Core Collection for Maize （Zea mays L.） Landrace from Wuling Mountain Region in China

Based on the genetic clustering from 42 microsatellite （SSR） markers with a combination of their geographic origin and germplasm characteristics, 124 maize landraces from Wuling Mountain region in China were used for constructing a core collection. Four evaluating parameters for maize landrace core collection, including mean difference percentage （MD）, variance difference percentage （VD）, coincidence rate of range （CR）, and variable rate of coefficient of variation （VR）, were assessed With 20 quantitative traits. It was shown that genetic relationships among landraces in Wuling Mountain region had the tendency to associate with their geographic origins. The 124 landraces were clustered into 18 subgroups when the coefficient of genetic similarity （GS） is 0.28. Eighteen landraces, each of which was from one subgroup, were applied to construct the core collection with a sampling percentage of 15%. Comparison of the initial and core collection indicated that there existed no significant differences in most quantitative traits. An average of 6.3 and 6.5 alleles were detected in the initial and core collection, respectively. Mean polymorphism information content in the core collection （0.75） was higher than that in the initial one （0.72）. MD was lesser than 20% and CR was more than 80%. The results showed that the sampling strategy would be feasible for constructing the core collection that well represents the genetic diversity of the initial one.     

Control Means and Data Analysis of Environmental Factors of Facility Watermelon in Beijing Area

In this study, the environmental indicators(including temperature, light, air relative humidity and CO_2 concentration) of facility watermelon in Beijing area were monitored with US350 environmental sensor during the whole growth period. The results showed that in the solar greenhouses in Beijing area, the average air temperature was in the range of 10.67-29.95 ℃ during the whole growth period of watermelon, the average soil temperature ranged from 16.92 to 35.10 ℃, the average light intensity changed from 268.37 to 13 842.60 lx, the average air relative humidity ranged from 52.40% to 94.26%, and the average CO_2 concentration was in the range of 455-631 ml/m~3; and in the spring greenhouses in Beijing area, the variation range of average air temperature was 14.05-29.84 ℃ during the whole growth period of watermelon, the average soil temperature ranged from17.47 to 28.12 ℃, the average light intensity was in the range of 55.80-12 858.64 lx, the average soil moisture content ranged from 18.19%-34.56%, the variation range of average air relative humidity was 20.72%-96.26%, and the average CO_2 concentration was in the range of 351-544 ml/m~3.     

GyrA and ParC Gene Mutation of Clinically Isolated Fluoroquinolones-resistant Strain of Salmonella

Nine strains resistant to five fluoroquinolones (Ciprofloxacin, Ofloxacin, Enrofloxacin, Danofloxacin, Sarafloxacin) were isolated from clinical samples and extracted the chromosomal DNA of these strains. Designed primers to amplify the Quinolone-resistance-determining region (QRDR) of gyrA and parC, then the PCR products were sequenced and analyzed. In comparision with NCTC5776, a single mutation was found at base 371 in gyrA of strain 38 which changed from C to T, and a single mutation was found at base 350 in gyrA of strain 60 which changed from A to C. No mutation was found in gyrA of the rest. The mutation of strain 38 led to an amino acid substitution of Arg99Cys and the mutation of 60 led to an amino acid substitution of Met 92 Leu. No mutation was found in parC QRDR of all the isolates. These results indicats that the DNA gyrase will be the primary target to salmonella of fluoroquinolone.     

Total Carbon Storage in Himalaya Rangeland of Milke-Jaljale Area,Eastern Nepal

Rangelands occupy 51% of the terrestrial land surface, 23% total land of Nepal. It contains about 36% of the world＇s total carbon in above and belowground biomass. Rangelands can aid in the mitigation of rising atmospheric carbon dioxide concentrations via carbon storage in biomass and soil organic matter. A study on carbon stock on soil and vegetation at various altitudinal gradients in Milke-Jaljale rangeland area of Eastern Nepal was made. The study was carried out at three altitudinal gradients （above sea levels） Milke （3,000 m）, Gorujure （3,500 m） and Jaljale （4,000 m）. This method required establishing a transect line. Sample points were located by pacing the appropriate distances from the point of origin at a transect line. To determine distribution and quantity of plant carbon and soil organic carbon （SOC）, 45 sample points were established and 15 points were sampled from each study site. Total soil carbon was estimated as follows： 17.65 t/ha at Milke, 17.27 t/ha at Gorujure and 28.33 t/ha at Jaljale. Similarly, total vegetation carbon was estimated 22.68 t/ha at Milke, 29.79 t/ha at Gorujure and 42.54 t/ha at Jaljale. Highest elevation study site with least external disturbance （Jaljale area） had high storage of carbon in both cases vegetation and soil.     

A Fractal Method of Estimating Soil Structure Changes Under Different Vegetations on Ziwuling Mountains of the Loess Plateau, China

Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension was used to study the soil structure in soil at different stages of vegetative succession on the Ziwuling Mountains. The land use and vegetation types included cultivated land, abandoned land, grassland, two types of shrub land, and three types of forests. The grassland, shrub land, and forested areas represented a continuum in vegetative succession that had occurred naturally, as the land was abandoned in 1862. Disturbed and undisturbed soil samples were collected from ten vegetation types from depths of 0-10, 10-20, and 20-30 cm on the Ziwuling Mountains, at a site with an elevation of about 1 500 m. Particle size distribution was determined by the pipette method and aggregate size distribution was determined by wet sieving. The results were used to calculate the particle and aggregate fractal dimension. The results showed that particle and aggregate fractal dimensions varied between vegetation types. There was a positive correlation between the particle fractal dimension and the weight of particles with diameter 〈 0.001 mm, but no relationship between particle fractal dimension and the other particle size classes. Particle fractal dimension was lower in vegetated soils compared to cropland and there was no consistent relationship between fractal dimension and vegetation type. Aggregate fractal dimension was positively correlated with the weight of 〉 0.25 mm aggregates. Aggregate fractal dimension was lower in vegetated soils compared with cropland. In contrast to particle fractal dimension, aggregate fractal dimension described changes in soil structure associated with vegetative succession. The results of this study indicate that aggregate fractal dimension is more effective in describing soil structure and function compared with particle fractal dimension.     

Evaluation on Heavy Metals in Black Soils of Hailun and Bayan Counties in Northeast China

The concentration of heavy metals was investigated in black soil samples collected from the fields treated with chemical in Bayan County which were from the vegetation covers,bare soil and grain fields without any chemical treatments in Hailun National Field Research Station of Agroecosystem,Chinese Academy of Sciences (CAS) in July,2009.Results showed that the presence of significantly high concentration of zinc (Zn) and lead (Pb) in soils covered with grass vegetation.However,mercury (Hg),copper (Cu),nick...     

Detecting Agro-Droughts in Southwest of China Using MODIS Satellite Data

The normalized difference vegetation index (NDVI) has proven to be typically employed to assess terrestrial vegetation conditions. However, one limitation of NDVI for drought monitoring is the apparent time lag between rainfall deficit and NDVI response. To better understand this relationship, time series NDVI (2000-2010) during the growing season in Sichuan Province and Chongqing City were analyzed. The vegetation condition index (VCI) was used to construct a new drought index, time-integrated vegetation condition index (TIVCI), and was then compared with meteorological drought indices-standardized precipitation index (SPI), a multiple-time scale meteorological-drought index based on precipitation, to examine the sensitivity on droughts. Our research findings indicate the followings: (1) farmland NDVI sensitivity to precipitation in study area has a time lag of 16-24 d, and it maximally responds to the temperature with a lag of about 16 d. (2) We applied the approach to Sichuan Province and Chongqing City for extreme drought monitoring in 2006 and 2003, and the results show that the monitoring results from TIVCI are closer to the published China agricultural statistical data than VCI. Compared to VCI, the best results from TIVCI3 were found with the relative errors of -4.5 and 6.36% in 2006 for drought affected area and drought disaster area respectively, and 5.11 and -5.95% in 2003. (3) Compared to VCI, TIVCI has better correlation with the SPI, which indicates the lag and cumulative effects of precipitation on vegetation. Our finding proved that TIVCI is an effective indicator of drought detection when the time lag effects between NDVI and climate factors are taken into consideration.     

百合脱毒技术研究进展

百合是重要的切花品种之一,长期的无性繁殖造成病毒在其体内大量积累。介绍了侵染百合的常见病毒种类,并详细叙述了通过热处理、茎尖组织培养脱毒、化学处理、玻璃化超低温处理法等获得无病毒苗的方法,以及病毒检测技术研究进展。     

宁夏水稻香味的研究进展

综述了水稻香味的特点和类型、香味的化学成分、遗传研究进展以及影响水稻香味的环境因素,并针对水稻香味研究提出了问题和建议。     

Unity in function in the absence of consensus in sequence: role of leader peptides in export

Passage of proteins across membranes during export from their site of synthesis to their final destination is mediated by leader peptides that paradoxically exhibit a unity of function in spite of a diversity of sequence. These leader peptides act in at least two stages of the export process: at entry into the pathway and subsequently during translocation across the membrane. How selectivity is imposed on the system in the absence of a consensus among the sequences of leader peptides is the main issue discussed here.     

新疆喀什市周边地区绵羊寄生蜱种类调查

2005年4月下旬，我们对喀什市周边地区绵羊寄生蜱种类进行了调查。鉴定出2个科11个属的17种蜱，其中有3属未做种的鉴定。     

从数字图书馆看21世纪我国图书馆工作的变化

本文探讨了在向数字图书馆发展的过程中我国图书馆在信息资源建设、服务功能、管理对象等方面的变化趋势。     

机油乳剂防治柑桔害虫的研究进展

机油乳剂对柑桔螨类、蚧类、粉虱类、蚜虫类、木虱、潜叶蛾等多种害虫具有理想的防治效果,而对天敌则较安全。旧式的、宽馏程范围的机油乳剂若使用不当易产生药害,随着本文的不断改进,机油乳剂的对害虫的防治效果更好而对植物更为安全,在柑桔害虫综合防治中发挥着越来越重要的作用,中澳合作研究的结果表明,机油乳剂在中国具有广阔的应用前景。     

我国苜蓿抗霜霉病的研究进展

介绍了霜霉病的症状和发生规律及病原菌的生物学特性，提出苜蓿霜霉病的防治更侧重于“防”，更依赖于科学的田间管理与草地利用等综合防治措施，即牧草混播、合理施肥、合理利用、搞好田间卫生、种子处理，最后指出了苜蓿育种工作中存在的主要问题。     

盘锦冬季日光温室小气候特征研究

为了进一步提高设施农业气象服务水平,对盘锦地区冬季日光温室小气候变化规律进行了分析。结果表明：不同天气条件下日光温室各月气温日变化趋势相似,均呈“单峰”曲线型。晴天和多云天气日光温室内相对湿度昼高夜低;阴天和雨雪天日光温室内相对湿度变化比较平稳。不同天气条件下冬季日光温室室内总辐射最大值出现月份不同,有无草帘对温室内总辐射值影响较大。     

柿组织培养技术研究进展

从培养基、外植体及培养方式等方面介绍了柿组织培养技术的研究进展，并讨论了柿组培过程中存在的褐变、生根难和玻璃化等问题及可能解决的途径。     

我国苜蓿褐斑病研究进展

苜蓿是农牧业发展中不可缺少的牧草之一。苜蓿褐斑病是由苜蓿假盘菌引起的一种最常见的世界性豆科牧草病害,对它的研究多数集中于褐斑病的田间病情调查与病原菌的鉴定。近年来,由于生物技术的迅速发展,国内的研究者开始对褐斑病进行一些比较深入的研究,本文对苜蓿褐斑病的研究进展做一介绍,不仅指出了存在的问题,同时还提出了一些建议,以供我国有关的科技人员和生产参考。