西北地区粮食问题,潜力和发展途径

西北地区因其特定的自然条件的制约和农业基础脆弱以及投入不足的影响，人均粮食占有量一直低于全国的平均水平，是粮食调入区。本文把西北地区粮食发展划分为四个阶段，分析了粮食增产的主要途径。通过对粮食近期增长潜力和宜农荒地潜力分析，预测西北地区本世纪末粮食可能增产的幅度，并提出了达到该目标应采取的技术措施。     

1995年中国西北东部特大干旱的气候诊断与卫星监测

对１９９５年出现在我国西北东部地区的特大干旱，选取相关资料进行分析，其特征得到了较深入的探讨。结果表明，１９９５年发生在我国西北地区的特大干旱其影响范围，持续时间及程度，均属历史之所罕见。植被指数可以很好地反映出干旱对植被生长的影响，１９９５年干旱发生区植被指数较往年偏低，重灾区下降幅度很大。     

西北太平洋: 21世纪的地理--政治枢纽

20世纪初,英国著名地理学家麦金德在其名著《历史的地理枢纽》一书中,通过对地理大发现以后世界政治地图,尤其是欧洲政治地图变化的分析,提出了“大陆腹地”的概念,并把中、东欧地区称为国际政治的“枢纽”地区。二战以后,美、英等西方国家正是基于麦金德的这一思路,把围堵“枢纽”地区作为其全球战略的重中之重,拉开了长达半个世纪的“冷战”帷幕。冷战结束以后,世界政治地理格局发生了重大变化,西北太平洋地区以其重要的地理位置、蓬勃发展的经济和急剧增长的军备,成为国际地缘政治中新的“枢纽”地区。本文从政治军事地理角度对这一问题进行了初步研究,供关心西北太平洋地区局势的同仁参考。     

Arcellaceans (thecamoebians) as indicators of land-use change: settlement history of the Swan Lake area, Ontario as a case study

Arcellaceans have been used as indicators of a variety of paleolimnological conditions including pH, eutrophication, oxygen level, and heavy metal contamination, but there has only been limited application of the group to climate and land-use change research. The limnological evolution of Swan Lake in southwestern Ontario was documented using arcellaceans as proxies, and compared to the results of a palynological analysis, with which it closely correlated. The palynological record documents the rapid disappearance of forest by around 1850 as the area was cleared for agriculture and settlements. The change was characterized by a shift in the palynological record from the Woodland to High Diversity assemblages. Similarly the arcellacean fauna changed from the Pre-European Settlement Assemblage to the distinctive low diversity, stressed environment European Deforestation Assemblage. The introduction of high-yield chemical fertilizers in the post World War II era, and the resultant eutrophication of the lake, was clearly recognizable in the palynological record as indicated by the dramatic increase in the algae Pediastrum (High Nutrient Assemblage). This change in farming practice was also identifiable with arcellacean proxies, as indicated by the appearance of the algalphilic Eutrophication Assemblage. The arcellacean Ecologically Destabilized Assemblage dominated the lake for short intervals during the transition between the Pre-European Settlement and European Deforestation assemblages and again at the transition between the European Deforestation and Eutrophication Assemblages, indicative of periods of ecological destabilization as the lake adjusted to new trophic inputs. A stressed environment arcellacean Ecologically Destabilized Assemblage found in a portion of the core estimated to have been deposited between AD 1350 and AD 1700 may provide evidence of an earlier phase of deforestation associated with Huron Indian agricultural practices. The close correlation between the palynological and arcellacean proxy data clearly demonstrates the potential of arcellaceans as land-use change proxies, and indicates that changes in land-use had an almost immediate impact on the Swan Lake ecosystem. This observation raises concerns about the impact that rapid urbanization is having on the environmentally sensitive Oak Ridges Moraine watershed, of which Swan Lake is a part.     

中国西北干旱区自然保护区生态脆弱性评价——以甘肃西湖、苏干湖自然保护区为例

依据中国西北干旱区生态环境的特性和演化规律,从气候条件、土地资源、生境状态及人为干预4方面筛选12个指标,构建西北干旱区自然保护区生态脆弱性评价指标体系,并对各指标进行分级.采用层次分析法确定指标权重,建立生态脆弱性综合评价模型.在甘肃敦煌西湖自然保护区和苏干湖自然保护区应用表明,指标体系合理,模型适用.评价认为,西湖自然保护区目前总体状态为中,高度脆弱,苏干湖自然保护区为轻,中度脆弱.在原生脆弱性方面,两者等级相当,但西湖更脆弱;在次生脆弱性方面,西湖已受到显著影响,次生脆弱性严重.     

Geological and geophysical evidence for pre-Nipissing (>5,000 years BP) transgression infilled valleys in the Lake Huron basin,Ontario

Lake Algonquin, the largest glacial lake of the Great Lakes area, ended prior to 10,000 years BP by drainage to the Ottawa Valley as the North Bay outlet was deglaciated. At that time, the outlet area was isostatically downwarped more than 100 m; resulting low water, river-linked lakes Chippewa, Stanley, and Hough, lowstands in the basins of lakes Michigan, Huron, and Georgian Bay respectively, were much below present lake level. While water levels were low, about half of the present lake area was dry land. The land above the lowstands was dissected by streams and became forested. Uplift of the North Bay outlet between 10,000 and 5,000 years BP raised lake level to above the present (the Nipissing transgression), submerging the forest and valley system. Submerged stumps from those forests have often been encountered on the present lake floor; some stumps have been dated. Four sites in Ontario (Parkhill, Owen Sound, St. Joseph Island, Meaford) provide on-land evidence of pre-Nipissing drainage and valley formation. Radiocarbon ages of valley fill organic materials range from 7,310 to 5,410 years BP. At three sites, present drainage is known to be displaced from the pre-Nipissing drainage. Geophysical methods (EM, GPR, resistivity) have been used to refine valley location and morphology at Parkhill and Meaford. There is the potential of tracing the valleys down slope to the low-water shorelines with shipboard geophysics, with implications for archaeology, hydrology and hydrogeology, paleogeography, and Great Lakes history. This is the eighth in a series of ten papers published in this special issue of Journal of Paleolimnology. These papers were presented at the 47th Annual Meeting of the International Association for Great Lakes Research (2004), held at the University of Waterloo, Waterloo, Ontario, Canada. P.F. Karrow and C.F.M. Lewis were guest editors of this special issue.     

BEFOLKMNGS- OG ERHVERVSUDVIKLINGEN PÅ RØMØ 1950–70

Engell. Bodil, 1977: Befolknings- og erhvervsudviklingen på Rømø 1950–70. Geografisk Tidsskrift 76: 63–67. København juni 1, 1977.

The general trend of unequal development between rural and urban intensifies on small islands. The development on the island of Rømø has further a special trend because of its intermediate position caused by the construction of the road-dam to Rømø, opened 1949. Furthermore, the recreational potential of the island and the special location close to the Danish-German border is of importance.     

Tidal harmonic analysis of TOPEX/POSEIDON data in the Northwest Pacific by introducing difference-ratio relations

The difference-ratio relations are introduced to separate tidal constituents that are aliaseddue to the sampling interval and sampling span of the TOPEX/POSEIDON altimeter. It is found that some tidal constituents such as K_1 and SSA, though aliased at along track points, are not aliased at crossover points Ixrausf the data at crossover points are double those at along track points. So the harmonic analysis method can be employed directly for the analysis of time series at crossover points. Then the difference-ratio relations from crossover points are introduced to analyze the time series at along track points. The TOPEX/POSEIDON data in the Northwest Pacific are analyzed with this method. The results from this method agree well with tidal constants from tidal gauges.     

Ontario’s Environmental Farm Plan: Evaluation and research agenda

This paper analyses the operation of the Environmental Farm Plan (EFP) scheme in Ontario, Canada, a voluntary agri-environment scheme established in 1993. Previously unpublished data and interviews with farmers, leaders of farmers’ organisations and government officials are used to detail participation rates, geographical spread and method of operation. Largely developed by farmers’ organisations, the scheme has focused on soil management, water quality and storage/disposal of agricultural wastes. The environmental actions associated with these activities are discussed, revealing both successes and limitations. Distinctions are drawn with agri-environmental schemes in the European Union, and a broader context for the EFP is provided with respect to the proposed post-productivist transition of agri-food systems and the need to examine the way these systems are regulated. A need for further systematic research is proposed, specifically with respect to barriers to participation, the voluntary nature of the scheme, financial incentives and the resultant environmental impacts.     

2001−2018年西北地区植被变化对气象干旱的响应

基于2001?2018年逐月的MODIS NDVI数据,以归一化植被指数（Normalized Difference Vegetation Index, NDVI）和植被状态指数（Vegetation Condition Index, VCI）作为植被生长状况指标,结合2001?2018年的月降水和月均温数据计算的标准化降水蒸散指数值,分析西北地区植被状况和气象干旱指数的变化趋势及其空间分布特征,以及多时间尺度下植被对气象干旱的响应。结果表明：2001?2018年西北地区植被的生长状况整体呈好转趋势,但空间分布上差异明显,东部植被改善状况高于中西部地区。近18 a西北地区5种不同时间尺度标准化降水蒸散指数（Standardized Precipitation Evapotranspiration Index,SPEI）均值整体上均呈增加趋势,表明干旱程度降低;空间上,干旱化趋势整体上表现为中西部高,东部低。植被生长状况在大部分区域均与SPEI呈现不同程度的正相关,总体表现为,西北地区东部植被对气象干旱的响应程度最高,西部次之,中部最低;不同植被类型中,草地对SPEI-12的响应最强,耕地次之,而林地的响应最弱;各植被类型在生长季的多数月份中对SPEI-3和SPEI-12的响应普遍较高。