南极中山站附近麦氏贼鸥食性研究          下载免费PDF全文

王自磐 《极地研究》1992,4(1):1-16

对东南极中山站附近麦氏贼鸥巢区和无巢贼鸥群栖地的贼鸥回吐渣团及其他食物残物进行收集、分析和鉴定 ,结果表明 ,本区麦氏贼鸥主要捕食雪　 ,其残物在食物项中的平均出现率为 6 7～ 80 %;同时贼鸥从本区几个考察站觅取人类遗弃的垃圾食物作为其重要的食物补充 ,垃圾食物的平均出现率为 6 .8～ 1 1 .6 %。不同巢区贼鸥对雪　的捕杀量和垃圾的需求差异较大 ,其主要与营巢地域的雪　分布密度以及摄食区的占有与否有关。  相似文献   

A meta-analysis of global crop water productivity of three leading world crops (wheat,corn, and rice) in the irrigated areas over three decades     

Daniel J. Foley  Itiya P. Aneece  Pardhasaradhi G. Teluguntla  Adam J. Oliphant 《International Journal of Digital Earth》2020,13(8):939-975

ABSTRACT

The overarching goal of this study was to perform a comprehensive meta-analysis of irrigated agricultural Crop Water Productivity (CWP) of the world’s three leading crops: wheat, corn, and rice based on three decades of remote sensing and non-remote sensing-based studies. Overall, CWP data from 148 crop growing study sites (60 wheat, 43 corn, and 45 rice) spread across the world were gathered from published articles spanning 31 different countries. There was overwhelming evidence of a significant increase in CWP with an increase in latitude for predominately northern hemisphere datasets. For example, corn grown in latitude 40–50° had much higher mean CWP (2.45?kg/m³) compared to mean CWP of corn grown in other latitudes such as 30–40° (1.67?kg/m³) or 20–30° (0.94?kg/m³). The same trend existed for wheat and rice as well. For soils, none of the CWP values, for any of the three crops, were statistically different. However, mean CWP in higher latitudes for the same soil was significantly higher than the mean CWP for the same soil in lower latitudes. This applied for all three crops studied. For wheat, the global CWP categories were low (≤0.75?kg/m³), medium (>0.75 to <1.10?kg/m³), and high CWP (≥1.10?kg/m³). For corn the global CWP categories were low (≤1.25?kg/m³), medium (>1.25 to ≤1.75?kg/m³), and high (>1.75?kg/m³). For rice the global CWP categories were low (≤0.70?kg/m³), medium (>0.70 to ≤1.25?kg/m³), and high (>1.25?kg/m³). USA and China are the only two countries that have consistently high CWP for wheat, corn, and rice. Australia and India have medium CWP for wheat and rice. India’s corn, however, has low CWP. Egypt, Turkey, Netherlands, Mexico, and Israel have high CWP for wheat. Romania, Argentina, and Hungary have high CWP for corn, and Philippines has high CWP for rice. All other countries have either low or medium CWP for all three crops. Based on data in this study, the highest consumers of water for crop production also have the most potential for water savings. These countries are USA, India, and China for wheat; USA, China, and Brazil for corn; India, China, and Pakistan for rice. For example, even just a 10% increase in CWP of wheat grown in India can save 6974 billion liters of water. This is equivalent to creating 6974 lakes each of 100?m³ in volume that leads to many benefits such as acting as ‘water banks’ for lean season, recreation, and numerous ecological services. This study establishes the volume of water that can be saved for each crop in each country when there is an increase in CWP by 10%, 20%, and 30%.  相似文献   

Differences in animal ¹³C, ¹⁵N and D abundance between a polluted and an unpolluted coastal site: Likely indicators of sewage uptake by a marine food web     

G.H. Rau  R.E. Sweeney  I.R. Kaplan  A.J. Mearns  D.R. Young 《Estuarine, Coastal and Shelf Science》1981,13(6):701-707

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我国粮食供给安全与耕地资源变化   总被引：6，自引：0，他引：6  

谭术魁  彭补拙 《世界地理研究》2002,11(4):12-17

实现粮食基本自给,主要依靠自己养活自己是我国政府奉行的粮食安全思路,因而国内耕地的维护工作始终倍受关注,但是结果仍然难尽人意。本文分析了耕地面积,耕地质量,耕地分布重心,耕地改良投入,耕地农用驱动力等多种威胁国家粮食供给安全的要素变化。  相似文献   

Carbon sources of fish in an Amazonian floodplain lake     

A. Cristina B. Oliveira  M. Gercilia M. Soares  L. Antonio. Martinelli  M. Zacarias. Moreira 《Aquatic Sciences - Research Across Boundaries》2006,68(2):229-238

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Diel and seasonal variability in the fish community structure of a mud‐bottom estuarine habitat in the Gulf of Mexico     

Manuel Castillo‐Rivera  Rocío Zárate‐Hernández  Selene Ortiz‐Burgos  José Zavala‐Hurtado 《Marine Ecology》2010,31(4):633-642

We hypothesized that temporal variation in fish species composition and community structure in a low complexity habitat in the Pueblo Viejo Lagoon, Mexico, is influenced by diel light/dark cycles and tidal stage, and by seasonal changes in salinity and temperature. We collected a total of 17,661 individuals during 2‐h interval sampling over six bi‐monthly 24‐h sampling cycles representing 53 species, of which 11 (～20%) were previously unknown in the system. Diel variation indicated that significantly higher numbers of individuals and species were caught at night, whereas diversity and evenness were higher during the day. Species richness was significantly higher in July and January, whereas diversity and evenness peaked around May; both were correlated with temperature. Diel variation in species composition was influenced primarily by the light/dark cycle. Cluster analyses of each diel cycle separated fish assemblages from midday samples from those of nocturnal samples, separated by an extended wide transition period as fish moved at dawn and during the late afternoon/dusk. Significant shifts (as determined by MANOVA) in assemblage structure occurred between months. Canonical correspondence analysis showed that temperature and day/night effects were the most important environmental variables structuring the fish community. This constrained ordination also defined species with specific habitat preferences as follows: (i) diurnal, warm temperature species (mainly planktivores) (Brevoortia gunteri, Cetengraulis edentulus, Diapterus auratus, and Membras martinica); (ii) nocturnal, warm temperature species (mainly predators) (Citharichthys spilopterus, Cathorops melanopus, and Bairdiella spp.); and (iii) low temperature, diurnal species (Brevoortia patronus and Mugil curema) or those with twilight and nocturnal distributions (Anchoa mitchilli, the most numerically abundant species). Our results indicate that diel and seasonal changes in fish community structure were mainly related to day/night cycles and temperature regimes.  相似文献   

GPS和GLONASS系统下RAIM空洞预报     

任锴  杨力 《全球定位系统》2009,34(4):25-28,36

接收机自主完好性监测（RAIM）是卫星导航系统完好性监测的方法之一。一定时空条件下的RAIM可用性，可以通过RAIM空洞直观的反映出来，可以为飞行提供预警；利用不同期GPS、GLONASS实际星座，仿真分析了单星座以及GPS／GLONASS组合星座RAIM可用性，绘制了RAIM空洞图，具有一定的参考价值。  相似文献   

人类世可持续发展背景下的远程耦合框架及其应用   总被引：1，自引：1，他引：1  

孙晶  刘建国  杨新军  赵福强  覃驭楚  姚莹莹  王放  伦飞  王洁晶  秦波  刘涛  张丛林  黄宝荣  程叶青  石金莲  张劲松  唐华俊  杨鹏  吴文斌 《地理学报》2020,75(11):2408-2416

在全球一体化进程不断加深的背景下,国家与地区之间的联系日益紧密,产生了一系列跨国家、跨地区、多尺度的社会—经济—环境影响,远程耦合（Telecoupling,社会、经济、环境的远距离相互作用）科学概念和综合框架的提出为解决上述问题提供了新方法和新途径。为更好促进远程耦合综合框架的正确使用和规范推广,本文系统解析了远程耦合综合框架,厘清各组成部分的定义和功能,梳理了框架的应用现状;通过对3个中国典型案例的阐释,展示了远程耦合综合框架的使用方法、结果分析及由此得出的科学意义和政策价值;最后描述了远程耦合综合框架使用中需要重点关注的问题,并对其应用前景进行了展望。远程耦合综合框架的推广应用有助于以跨国家、跨地区、多尺度的视角,重新审视多个人类与自然耦合系统的相互作用,揭示隐藏的远距离地理空间作用的科学价值,服务于有关政策的制定和实施,促进全球社会、经济、环境的可持续发展。  相似文献   

Effects of Body Weight and Water Temperature on Maximum Food Consumption of JuvenileSebastodes fuscescens (Houttuyn)     

谢松光  杨红生  周毅  张福绥 《中国海洋湖沼学报》2004,22(1)

1　INTRODUCTIONTherateoffoodconsumptionoffishfedadlibitumisregardedasthemaximumrateoffoodconsumption(Cmax) (Woottonetal.,1 980 ) .SeveralfactorsthatinfluenceCmaxincludingbodyweight (Liuetal.,1 998) ,watertemperature (Liuetal.,1 998) ,dis solvedoxygen (Vivekanandan ,1 977) ,salinity (ZanuyandCarrillo ,1 985 ) ,andphotoperiod (Grossetal.,1 965 ) ,werereported .Bodysizeandwatertemperaturewereregardedastwoofthemostimportantfactors,andhadreceivedmostattention (Elliott,1 979;Woottonetal.,1 …  相似文献   

中国居民食物消费碳排放时空演变趋势及其驱动机制分析     

曹志宏  郝晋珉  邢红萍 《地理科学进展》2020,39(1):91-99

食物生产是影响温室效应气体排放的重要方面,由于食物类型不同其碳排强度存在较大的差异,因此当前中国居民食物消费快速演替必然会对生态碳环境产生重要影响。论文利用洛伦兹曲线和基尼系数,研究1997—2016年中国城乡居民食物消费在生产过程中碳排放时空演变及其主要驱动因子。主要结论如下：① 在数量上,中国居民食物消费碳排放总量和人均量整体都呈现逐渐的增长刚性,但仍属于低碳消费模式;② 在结构上,各类型食物碳排放演变呈现显著的分异态势,整体上动物性食物碳排放增长速度快于植物性食物碳排放减少速度;③ 在城乡差异上,城镇和乡村居民食物消费碳排放在数量、结构和趋势上表现出显著的城乡二元属性,但近年城乡差异表现出减缓趋势;④ 在空间上,各地食物消费碳排放呈现较显著的民族性、地域性、集聚性和中心“塌陷”的特征,碳排放密度高值主要分布在直辖市和沿海经济相对发达地区;⑤ 在驱动力上,结构演替是全国居民食物消费碳排放总量整体变化的主要驱动因素,而人口数量是各地地域空间差异分布的主要驱动因子。  相似文献