红壤丘陵区土地利用变化对土壤质量影响

以鄂南红壤丘陵典型区的三个村为代表 ,应用地理信息系统对 1981和 1998年两个时期的土地利用变化和土壤质量进行对比研究 ,分析了土地利用变化对土壤质量的影响。结果表明 :研究区土地利用结构总体上具有农业型特点 ,17a间水田减少了 2 1% ;其余的利用方式则有不同幅度的增加 ,居民地、水域、林地、园地和旱地增加了 4 2 .2 %、99.6 %、8%、5 6 .8%和 8%。土壤质量有从优劣两端向中等靠拢的趋势 ,17a后 、 、 和 等地面积分别减少 18.6 %、12 .2 %、2 9.6 %和 2 5 % ; 等地增幅达 5 1.9%。土地利用方式及管理措施是影响土壤质量演变方向和强度的关键因子 ,园地和林地的土壤质量大多得到明显改善 ,水田的Δ SQI多数呈下降的趋势 ,旱地的土壤质量变化比较复杂 ,与土地利用结构相关。依此 ,本文探讨了定向培育土壤质量的途径     

Environmental and Economic Factors Can Increase the Risk of Exotic Species Introductions to the Arctic Region Through Increased Ballast Water Discharge

The effects of global warming can increase the risk of exotic species introductions in eastern Canadian Arctic waters by reducing surface ice cover and allow increased access to commercial vessels. Ballast water discharged by incoming overseas vessels is an important means for introducing species on a global scale. Analyses of air temperatures at Churchill, Manitoba between 1943 and 2002 indicated an increase in mean temperature within the past decade. Churchill is the only major northern port in this region where grain has been exported on a limited basis due to the short navigation season. Economic analyses of grain exported from Canadian and U.S. ports indicated some cost advantages for using northern ports. The Hudson Bay region is vulnerable to increased exotic species introductions because of its southerly location. Current ballast water exchange measures to reduce the risk of introductions may not be effective because most vessels enter the region with ballast, and the ballast exchange zone is located relatively close to coastal areas where the habitat could be favorable for an introduced species to become established. The probability of a large crab species introduced to this region from northern European waters is discussed. The risk of ballast water–related exotic species introduction to this region may be reduced by expanding the types of cargo handled and developing a strong import market. This approach would accommodate an increase in the number of vessels with cargo, and substantially reduce the volume of ballast carried to this region.     

Quantitative Assessment of Agricultural Runoff and Soil Erosion Using Mathematical Modeling: Applications in the Mediterranean Region

Three mathematical models, the runoff curve number equation, the universal soil loss equation, and the mass response functions, were evaluated for predicting nonpoint source nutrient loading from agricultural watersheds of the Mediterranean region. These methodologies were applied to a catchment, the gulf of Gera Basin, that is a typical terrestrial ecosystem of the islands of the Aegean archipelago. The calibration of the model parameters was based on data from experimental plots from which edge-of-field losses of sediment, water runoff, and nutrients were measured. Special emphasis was given to the transport of dissolved and solid-phase nutrients from their sources in the farmers' fields to the outlet of the watershed in order to estimate respective attenuation rates. It was found that nonpoint nutrient loading due to surface losses was high during winter, the contribution being between 50% and 80% of the total annual nutrient losses from the terrestrial ecosystem. The good fit between simulated and experimental data supports the view that these modeling procedures should be considered as reliable and effective methodological tools in Mediterranean areas for evaluating potential control measures, such as management practices for soil and water conservation and changes in land uses, aimed at diminishing soil loss and nutrient delivery to surface waters. Furthermore, the modifications of the general mathematical formulations and the experimental values of the model parameters provided by the study can be used in further application of these methodologies in watersheds with similar characteristics.     

GEOMORPHIC PARAMETERS PREDICT HYDROGRAPH CHARACTERISTICS IN THE SOUTHWEST1

ABSTRACT: Critical design characteristics of ephermal runoff such as hydrograph rise time, duration, mean peak discharge, volume, peak-volume ratio, and maximum flood were related to physical basin parameters such as area, shape, slope, drainage density, basin relief, stream length, and combinations of these in intermontane watersheds representative of the Mexican Highland section of the Basin and Range Province. Parameters used were restricted to those easily obtainable from maps or aerial photographs. A parameter expressing basin shape and size was developed which proved to be as accurate a predictor as others used in existing prediction equations tested and was simpler and faster to derive. Simple prediction equations derived for hydrograph characteristics were all significant except for volume at the 5% level; three were significant at the 1% level. Relationships determined are applicable in semi-arid basins of the Southwest up to 60 square miles (155 km²) in area.     

烟台地区在业人口就业结构分析

根据人口普查资料，本文从行业和职业方面对烟台地区在业人口的就业结构现状及变动特点进行了系统分析，并在此基础上对农业剩余劳动力的转移问题作了深入探讨。     

西南岩溶石山地区岩溶水资源合理开发利用模式

针对湘西洛塔岩溶区特殊的地质环境所造成的干旱缺水、水土流失、生态环境恶化等问题的特点，在调查、分析洛塔自然条件与水土资源、生态环境基本条件的基础上，实施了13处岩溶水资源开发利用示范工程。通过系统总结洛塔地区岩溶水资源合理开发利用技术与方法及岩溶水资源开发利用成功经验，提出了以岩溶水小流域为单元对岩溶水资源进行综合开发利用的5种模式：①地下河堵洞引水开发利用模式；②地下河出口及岩溶大泉引水开发利用模式；③凿引水隧洞拦截地下河开发利用模式；④地表地下联合水库开发利用模式；⑤表层岩溶泉开发利用模式。通过对失败工程的案例分析，认为在岩溶水资源开发利用过程中，应查清工程的岩溶发育规律及工程地质条件，分析经济技术支持的可行性，然后采取相适应的开采方式与方法。岩溶水资源进行综合开发利用的5种模式的提出，为在湘西实施“水源〖DK1〗·土地〖DK1〗·生态”持续发展战略，发展生态经济，实现脱贫致富，促进社会经济、生态环境良性循环，提供了切实可行的实用技术与方法借鉴。     

基于RS&GIS的长白山地区生态安全评价研究

以遥感影像数据、专题数据、DEM数据、气象站实测数据和统计数据为数据源,采用极差法、层次分析法、综合指数法、RS&GIS等方法对长白山地区的生态安全进行了评价.结果表明:长白山地区生态安全水平呈现出明显的空间差异性,整体由中部向东西两端逐渐降低.各生态安全等级面积从大到小为临界安全等级、较安全等级、不安全等级、较不安全等级、安全等级.统计了各行政单元的平均生态安全指数和等级构成,各县市生态安全水平从高到低为长白县、抚松县、安图县、和龙市、临江市,各县市的生态安全等级构成也有所差异.长白山地区生态安全水平以临界安全等级为主,整体上生态环境质量一般,系统服务功能受到了一定程度的破坏.     

长江近口段沿岸刀鲚生物量的时间格局

为了解长江刀鲚Coilia nasus资源的变动状况,探讨沿岸水域对刀鲚资源的保育作用,于2002~2013年间用定制张网对长江靖江段沿岸鱼类作了每月2~3个样本的采集。分析结果显示,12a采集的369份样品中,刀鲚的出现频率达94.6%,分别占总渔获数量和重量的5.18%和5.46%。刀鲚平均CPUEN和CPUEW有16.7±19.9尾和106.6±109.5g,是沿岸鱼类群聚的优势种或次优势种。但其年资源量并不稳定,最高的2010年是最低2002年的5.4陪。平均体长123.6±37.0mm,平均体重仅7.5±8.2g。0+龄组占78.9%,1+龄组占20.7%,2+龄仅出现在4、5月份,且仅占当月个体数的3.0%,幼体是沿岸刀鲚群体的主要组成成分。从0+龄个体的月度体长分布看,当年孵化的幼鱼大多栖息在河岸水域,沿岸生境在维持刀鲚幼鱼资源上具有重要作用。分析显示,4月1日至6月30日的长江禁渔期虽可保护约42.6%的幼鱼个体,但从保护效果看,还因适当延长沿岸水域的禁渔时间。维护沿岸水域的生境完整性,也是保护长江刀鲚幼鱼资源的重要措施。