Diets of mammalian herbivores in Australian arid, hilly shrublands: seasonal effects on overlap between euros (hill kangaroos), sheep and feral goats, and on dietary niche breadths and electivities     

Terence J. Dawson  Beverley A. Ellis 《Journal of Arid Environments》1996,34(4):491-506

The diets of euros or hill kangaroos (Macropus robustus), domestic sheep (Ovis aries) and feral goats (Capra hircus) in hilly, shrub rangeland in southern Australia were examined in a 12-year study. Levels of dietary overlap between these herbivores, their foraging in relation to resource availability, and the potential for competition in different conditions were also examined. The diet of euros was based around grasses. In dry seasons some shrubs were also eaten but in severe drought grass formed more than 80% of their diet. While grass was important to sheep in wetter conditions, they ate much shrub in dry conditions. Feral goats had broad diets but their preference for browse was high. In drought, euros had only a modest dietary overlap with sheep and goats. Data for dietary niche breadths and electivities pointed to only limited competition between the herbivores.  相似文献   

以测绘职业技能竞赛为导向的课程改革实践探索——以工程测量技术专业课程改革为例     

赵丽蓉  陈帅 《测绘与空间地理信息》2016,(3):222-224

通过近年来测绘职业技能大赛的举办,测绘职业技能竞赛对课程改革的导向功能逐渐显现。本文以工程测量技术专业课程改革为例,重点探讨了测绘职业技能竞赛在课程改革方面发挥的导向作用,展示了我院工程测量专业在课程改革中初步取得的成效。  相似文献   

浅析工程测量竞赛中的测图方法     

冯传勇  杨柳 《测绘与空间地理信息》2016,(8):192-194

目前,国家测绘地理信息局已经举办了4届工程测量竞赛,外业测图是工程测量操作部分最常见的比赛形式。针对具体的比赛规则,先后实践了多种测图方法。本文将对几种典型的测图方法进行系统的总结和比对,并提出一套高效、可行的外业测图完整解决方法,目前,该方法已成功应用于长江委第八届工程测量竞赛、湖北省第四届工程测量竞赛、全国第四届工程测量竞赛中,并取得了理想的效果。  相似文献   

武汉地区自然光照度及其在光敏核不育上的应用     

谷德高 《南京气象学院学报》1994,17(4):512-515

通过对自然光３年的逐日观测表明，一定照度的光时受天气状况影响发生明显变化，晴天光时长、阴雨天光时短，低温伴随着短光时。武汉地区光照度（Ｅ）大于５０ｌｘ，光时大于１３ｈ ４５ｍｉｎ的持续时间是６月￣８月１日，该时段内基本可满足光敏核不育的光照条件。  相似文献   

中国农业的比较优势和国际竞争力   总被引：5，自引：0，他引：5  

程春梅 《世界地理研究》2001,10(2):96-100

加入WTO后，中国农业将面临严峻的挑战，为了应对入世的挑战，首先必须朋全球的视角考察我国农业的比较优势和国际竞争力，国际比较分析表明，我国农业并无明显的比较优势，国际竞争力也较弱，为此，必须及早采取措施，提高我国农业的国际竞争力，在分析论证的基础上，本文提出了调整行业结构，给予政策扶持、加大城镇化力度等对策建议。  相似文献   

地勘企业的可持续发展问题分析     

褚庆忠 《南方国土资源》2002,15(1):61-64

地勘企业是我国重要的基础工业企业 ,其可持续发展是国民经济发展的重要保证。文章从地勘企业的发展现状入手 ,阐述了地勘企业可持续发展的含义与研究意义 ,在借鉴国外地勘企业可持续发展经验的基础上 ,结合中国的实际情况 ,提出了地勘企业可持续发展的建议。  相似文献   

柱撑蛭石吸附去除废水中重金属离子的实验研究   总被引：2，自引：0，他引：2  

刘云  吴平霄  党志 《矿物岩石》2006,26(4):8-13

分别利用有机柱化剂十二烷基磺酸钠(SDS)和无机柱化剂聚羟基铝(HA)对蛭石进行柱撑制得十二烷基磺酸钠柱撑蛭石(SDS-V erm icu lite)和聚羟基铝柱撑蛭石(HA-V erm icu lite),并通过XRD、红外光谱、ZETA电位等表征手段对柱撑蛭石进行表征,同时针对柱撑蛭石对Cu2 ,Cd2 ,C r3 3种重金属离子的吸附进行研究,结果表明:吸附去除率受反应时间、重金属离子的初始浓度、pH值等因素的影响,经柱撑后的蛭石对重金属离子吸附的吸附性能比蛭石原矿要强。柱撑蛭石吸附3种重金属离子的动力学吸附过程可用E lov icb方程和双常数方程进行较好的拟合。  相似文献   

The Role of Residential Location in Conditioning the Effect of Metropolitan Economic Structure on Male Youth Employment     

Steven R. Holloway 《The Professional geographer》1998,50(1):31-45

Youths have increasingly experienced labor market problems over the last several decades. One fruitful line of explanation focuses on structural changes in the demand for labor stemming from deindustrialization, changing skill requirements for employees, and increasing supply competition from women and recent immigrants. While these explanations merit attention, they have not adequately considered facts that condition their impact. This paper considers the argument that intra-metropolitan residential location conditions the effects of metropolitan labor market structure on black and white male youths' employment probabilities. Using a sample of individual-level data drawn from the 1990 census combined with metropolitan-level indicators of economic structure, it was found that some structural effects varied between central-city and suburban male youths. The conditioning role of residential location, and the subsequent nature of the structural effects, varied considerably between black and white male youths. Interpretations of the conditioning role of residential location include a variety of social and institutional effects on individual residents and the stigmatizing effects of some neighborhoods, especially on black male youths.  相似文献   

An Experimental Test of the Capacity of Food Web Interactions (Fish–Epiphytes–Seagrasses) to Offset the Negative Consequences of Eutrophication on Seagrass Communities     

E. Gacia  M. M. Littler  D. S. Littler   《Estuarine, Coastal and Shelf Science》1999,48(6):757

A mechanism of competition between epiphytes and seagrasses potentially modulated by grazers was studied in a high-nutrient Thalassia testudinum meadow in the Indian River Lagoon (Florida, U.S.A.). The effects of fish grazing on epiphytes, and likely enhancing T. testudinum growth, was tested through an exclusion experiment. Twelve (2×2m) independent experimental plots were selected within a shallow monospecific bed to which three randomized treatments (exclusion fences, open fences and controls) with four replicates each were assigned. The epiphyte load was monitored on T. testudinum leaves inside the plots from January 1995 to March 1996. Treatment effects occurred during a chlorophyte bloom in March 1995, when the epiphyte biomass was significantly higher inside the exclusion cages than in either of the controls. The composition of the epiphytic community in March 1995 was dominated by sheet-like Enteromorpha and filamentous algae such as Cladophora , which are less resistant to herbivory than the coarsely-branched forms of red algae (e.g. Hypnea , Chondria and Acanthophora) that bloomed subsequently. These results suggest that herbivory change seasonally depending on the availability of different prey species to fish-grazers, which preferentially utilize the fleshy green algae typical of bloom conditions over the thicker coarsely-branched red algae. In the nutrient-rich lagoon the role of top-down interactions in enhancing T. testudinum growth is limited to the reduction of shading by green macroalgae.  相似文献   

对地勘单位贯彻ISO9000《质量管理和质量保证》系列标准的几点认识     

沈小荣 《青海国土经略》2000,(1)

ISO9000系列标准是一套国际统一的质量管理标准,应用的主体内容是质量管理模式(质量体系)的建立与运行。其对地勘单位走向市场,到社会投标、承揽地勘项目,保证地勘工作成果质量,提高单位在地质市场中的信誉度具有十分重要的意义。  相似文献