澜沧江上游德钦县亚高山、高山草地群落类型及其特点   总被引：1，自引：0，他引：1  

包维楷  吴宁  和绍春  阿追  革玛江初  杨沛芳  忠永次里 《山地学报》2001,19(3):226-230

摘要：采用样方调查方法获得94个草地群落样方,对澜沧江上游德钦县亚高山、高山草地群落类型及其特点进行了初步分析。结果表明,该县亚高山、高山草地群落类型存在20个类型。在放牧干扰下,大多数群落类型处于退化状态,相互之间存在明显的群落替代关系;调查发现群落中每平方米内平均含8种草本植物,平均盖度62．4％,地上平均生物量是4859kg／hm^2,平均可食率为61．5％;鸢尾群落、牛旁群落和小狼毒群落是草地严重退化后形成的典型有毒害群落类型;长期的高强度放牧虽然增加了群落类型多样性,但减少了群落内物种多样性。总体而言,长期的放牧干扰降低了德钦草地的生物多样性的质量及其生态服务功能,导致草地生态系统的非持续发展。  相似文献   

Ethanol Production: Energy and Economic Issues Related to U.S. and Brazilian Sugarcane   总被引：1，自引：0，他引：1  

David Pimentel  Tad Patzek 《Natural Resources Research》2007,16(3):235-242

For a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from sugarcane in both the U.S. and Brazil, every energy input in the biomass production and ultimate conversion process must be included. In this study, more than 12 energy inputs in average U.S. and Brazilian sugarcane production are evaluated. Then in the fermentation/distillation operation, nine more fossil fuel inputs are identified and included. Some energy and economic credits are given for the bagasse to reduce the energy inputs required for steam and electricity. Based on all the fossil energy inputs in U.S. sugarcane conversion process, a total of 1.12 kcal of ethanol is produced per 1 kcal of fossil energy expended. In Brazil a total of 1.38 kcal of ethanol is produced per 1 kcal of fossil energy expended. Some pro-ethanol investigators have overlooked various energy inputs in U.S. and Brazilian sugarcane production, including farm labor, farm machinery, processing machinery, and others. In other studies, unrealistic low energy costs were attributed to such energy inputs, as nitrogen fertilizer, insecticides, and herbicides. Both the U.S. and Brazil heavily subsidize ethanol production. Thus billions of dollars are invested in subsidies and this significantly increases the costs to the consumers. The environmental costs associated with producing ethanol in the U.S. and Brazil are significant but have been generally overlooked. The negative environmental impacts on the availability of cropland and freshwater, as well as on air pollution and public health, have yet to be carefully assessed. These environmental costs in terms of energy and economics should be calculated and included in future ethanol analyses so that sound assessments can be made. In addition, the production of ethanol in the U.S. and Brazil further confirms that the mission of converting biomass into ethanol will not replace oil. This mission is impossible. General concern has been expressed about taking food crops to produce ethanol for burning in automobiles instead of using these crops as food for the many malnourished people in the world. The World Health Organization reports that more than 3.7 billion humans are currently malnourished in the world—the largest number of malnourished ever in history.  相似文献   

Ozone Production Efficiency in Savanna and Forested Areas during the EXPRESSO Experiment     

T. Marion  P. E. Perros  R. Losno  E. Steiner 《Journal of Atmospheric Chemistry》2001,38(1):3-30

NO, NO_x, NO_y and O₃ have been measuredduring the airborne EXPRESSO experiment, November 96,which took place near Bangui (Central Africa) at thebeginning of the dry season. This period correspondsto an intense burning activity. Chemical andphotochemical characteristics of the planetaryboundary layer, which corresponds most of the time tothe monsoon layer, and the Harmattan layer, which issituated above the latter, have been studied forsavanna as well as rain forest areas. These two layersare very different when considering the chemicalcomposition (especially for ozone and NO_z) andthe photochemical age.The relationship of photochemical ozone productionversus photochemical NO_x oxidation products hasbeen investigated. Results indicate an ozoneproduction efficiency (OPE) ranging from 6.3 to 14.8in the planetary boundary layer. Thus, this layer ischaracteristic of a photochemically young and activeair mass. In this layer, the ozone potentialproduction increases with the air mass photochemicalage. On the other hand, the Harmattan layer shows anOPE ranging from 4.6 to 7.4. These values arecharacteristic of photochemically well-aged airmasses. In this layer, the ozone potential productionseems to be exhausted with values around 4.0 (i.e., 4ozone molecules produced for each NO_x moleculeemitted).  相似文献   

中国南京与美国德克萨斯稻田甲烷排放的比较   总被引：8，自引：0，他引：8  

Huang Yao  Jiang Jingyan  Zong Lianggang  Ronald L. Sass  Frank M. Fisher 《大气科学进展》2001,18(6):1121-1130

Field measurements of methane emission from rice paddies were made in Nanjing, China and in Texas, USA, respectively. Soil temperature at approximately 10 cm depth of the flooded soils was automatically recorded. Aboveground biomass of rice crop was measured approximately every 10 days in Nanjing and every other week in Texas. Seasonal variation of soil temperature in Nanjing was quite wide with a magnitude of 15.3℃ and that in Texas was narrow with a magnitude of 2.9℃. Analysis of methane emission fluxes against soil temperature and rice biomass production demonstrated that the seasonal course of methane emission in Nanjing was mostly attributed to soil temperature changes, while that in Texas was mainly related to rice biomass production. We concluded that under the permanent flooding condition, the seasonal trend of methane emission would be determined by the soil temperature where there was a wide variation of soil temperature, and the seasonal trend would be mainly determined by rice biomass production if there are no additional organic matter inputs and the variation of soil temperature over the rice growing season is small.  相似文献   

无谋干热河谷按树人工林生物量初步研究   总被引：8，自引：0，他引：8  

杨忠  张建平  王道杰  张信宝 《山地学报》2001,19(6):503-510

干热河谷人工林生长缓慢，林分结构简单，群落生物量较低。地面物质组成和地表侵蚀状况是影响干热河谷林木群落生物量的主要立地因素之一，土壤入渗能力强的石质山地有利于高大乔木的生长，桉树人工林生物量高，而侵蚀严重的泥质山地则相反，不利于高大乔木的生长，桉树人工林生物量低。  相似文献   

白令海蓝细菌分布   总被引：1，自引：0，他引：1       下载免费PDF全文

肖天  孙松  张武昌  李超伦  金明明 《极地研究》2001,13(1):13-20

1999年 7月～ 9月中国首次北极考察期间 ,研究了白令海 2个断面 8个站位海洋蓝细菌数量分布。蓝细菌数量变化在 0～ 7.93× 1 0 3 cell/ml之间 ,水平分布自南向北随纬度的增高而降低 ,在 6 0°N以北的 B1 - 1 2站没有检测到蓝细菌。垂直分布主要分布于 5 0 m以浅 ,最大值出现在B1 - 1站的 2 5 m水深。蓝细菌数量在 5 0 m以下迅速减少 ,到 1 5 0 m水深几乎没有。海水温度和NH+ 4 - N可能是影响蓝细菌数量分布的重要因素  相似文献   

应用Landsat ETM数据估算鄱阳湖湿生植被生物量   总被引：35，自引：1，他引：35  

李仁东  刘纪远 《地理学报》2001,56(5):532-540

利用2000年的Landsat ETM数据,首次采用全数字化遥感定量方法对鄱阳湖湿生植被的生物量及其分布进行调查研究.首先,用该时相卫星数据制作假彩色合成图象,以该图象为主要依据之一,设计了野外生物量采样路线与样点,并在地形图和GPS的帮助下,实时地开展了湿生植被生物量的野外实地采样.然后,在室内将采样点坐标和Landsat ETM图象坐标进行几何纠正和匹配,将坐标统一转换为等积圆锥投影.再逐个坐标点比较采样数据与ETM4波段数据和NDVI、DVI和第一主成分数据之间的线性相关关系.统计分析的结果表明,采样数据与ETM 4波段数据有最好的正相关,其相关系数达到0.86.采样数据与DVI、NDVI数据的相关系数分别为0.83、0.80.采样数据与第一主成分数据之间的相关关系不显著,仅0.40.基于这一比较,建立了采样数据与ETM 4波段数据的线性相关模型.据此,用ETM 4波段计算出鄱阳湖4月份湿生植被的总生物量为3.8×109 kg,并编制了整个湖泊生物量的分布图.  相似文献   

去除废水中重金属的低成本吸附剂:生物质和地质材料的环境利用   总被引：27，自引：0，他引：27  

王焰新 《地学前缘》2001,8(2):301-307

经济、有效、易获得的生物质和地质材料 (及二者的废弃物 )可用来取代传统的活性炭或离子交换树脂用于去除废水中的重金属。已经公开发表的低成本吸附剂主要可分为两类 :(1)生物质 (包括林业和农业的废弃物 ) :树皮 /富含丹宁酸的物质 ,木质素 ,几丁质 /甲壳质 ,死的生物体 ,苔藓 ,海草 /海藻 /褐藻酸 ,废弃的茶叶 ,稻壳 ,羊毛 ,棉花等 ;(2 )地质材料 (包括矿物利用后的工业废弃物 ) :沸石 ,粘土 ,泥炭 ,有铁氧化物包壳的砂 ,粉煤灰等。其中 ,对于重金属具有强吸附能力的吸附剂有甲壳质、沸石和木质素 ,例如 ,它们对一些重金属的最大吸附能力分别为 :甲壳质对Cd ,Hg ,Pb分别为 5 5 8,112 3 ,796mg/g ,沸石对Pb为 15 5 4mg/g ,木质素对Pb为 15 87mg/g。地质材料的环境利用值得引起地学界和环境工程界更广泛的重视。基于地质材料和水岩相互作用机理的环境污染控制技术有望成为 2 1世纪重要的环保替代技术。由于缺少连续的可比性强的成本信息 ,要比较不同的生物质和地质材料的成本和吸附性能仍较困难。尽管已对低成本吸附剂领域进行了很多研究 ,但要更好地了解低成本吸附剂的作用机理及其实用性 ,仍需要做大量的室内和现场工作。  相似文献   

Remote sensing-modelisation approach for diurnal estimation of burnt biomass in the Central African Republic Savanna     

M. Moula  J. M. Brustet  J. Fontan 《Journal of Atmospheric Chemistry》1996,25(1):1-19

Experimental studies and mesoscale modeling of atmospheric chemistry require a good knowledge of the sources of the atmospheric constituent, at a temporal scale of about one hour and at a spatial scale corresponding to the model grid. A combined remote sensing/modeling approach for the estimation of the diurnal distribution of the amount of biomass burning in Central African Republic (C.A.R.) savanna fires is proposed. The fire propagation model (BEHAVE) developed by Rothermel was adapted to the fuel characteristics encountered in C.A.R. Ground and airborne measurements with satellite images (NOAA/AVHRR) were used to predict an accurate estimate of the burnt biomass. This combination allows the calculation of the distribution of the number of fires during the day providing an evaluation of the instantaneous fluxes of the compounds emitted in the atmosphere by these fires.  相似文献   

距今14亿年低生物量的碳同位素证据   总被引：9，自引：0，他引：9       下载免费PDF全文

钟华  陈锦石 《地质科学》1992,(2):160-168

北京十三陵和天津蓟县两剖面中距今十四亿年海相碳酸盐岩的碳同位素表明,十三陵—蓟县地区当时具有较低的δ¹³C 值(共分析了152个样品),平均占δ¹³C=-0.7‰(PDB)。这种较低的δ¹³C 值很可能具有全球性。原始的海相碳酸盐岩较低的碳同位素组或反映较低的有机碳埋藏速率。有机碳的埋藏速率与当时全球生物量的大小有着密切的关系。磷酸盐岩较低的δ¹³C 值进一步反映当时较小的全球生物量的存在。每年8.11×10⁸吨有机碳推测是距今十四亿年全球生物量的最小值。  相似文献