Phosphorus export by runoff from agricultural field plots with different crop cover in Lake Taihu watershed

ＩｎｔｒｏｄｕｃｔｉｏｎＷａｔｅｒｅｕｔｒｏｐｈｉｃａｔｉｏｎｉｓｏｎｅｏｆｔｈｅｇｌｏｂａｌｅｎｖｉｒｏｎｍｅｎｔａｌｐｒｏｂｌｅｍｓ ,ａｎｄａｇｒｉｃｕｌｔｕｒａｌｎｏｎｐｏｉｎｔｓｏｕｒｃｅｐｏｌｌｕｔｉｏｎｈａｓｂｅｅｎｇｉｖｅｎｉｎｃｒｅａｓｅｄａｔｔｅｎｔｉｏｎ (Ｓｈａｒｐｌｅｙ ,1994 ;Ｈａｒｒｉｓ ,1995;Ｔｉｅｓｓｅｎ ,1995;Ｔｏｎｄｅｒｓｋｉ,1996;Ｄａｎｉｅｌ,1998) .Ｌａｋｅｅｕｔｒｏｐｈｉｃａｔｉｏｎｈａｓｂｅｅｎｉｄｅｎｔｉｆｉｅｄａｓａｃｒｉｔｉｃａｌｐｒｏｂｌｅｍｏｆｓｕｒ…     

广东省耕地地力等级研究与评价

广东省耕地地力等级研究与评价工作根据《全国耕地类型区、耕地地力等级划分》标准为依据，以土种为评价单元，采用的方法有归纳法、限制因素法、专家经验法，建立了省级土种数据库、耕地地力评价指标体系，并对各等级耕地进行面积统计、科学评价。研究结果表明，广东省水稻田地力等级分为八个等级，以一至四等为主，占水稻田总面积的87．1％；一、二等的水稻田占水稻田总面积的32．3％，是高产稳产农田；三至八等水稻田占水稻田总面积的67．7％，是粮食生产的主要基地，也是主要的中低产水稻田。必须针对后者的障碍因素，因地制宜采取不同的改良措施，加强改造，提高地力。旱地地力分为九个等级，全省高产旱地比例较低，一至四等旱地只占旱地总面积的7．9％，五至八等旱地占旱地总面积的73．79％，是经济作物和水果的主要生产基地。低产的旱地在田间管理上必须重视施用有机肥，增加土壤粘粒，培肥地力，提高作物产量，促进农业生产的发展。     

广东省坡耕地状况及其利用改良对策

广东省坡耕地面积６６．７９万ｈｍ２，占耕地总面积的２３．４８％．是广东省旱粮、油、糖、烟、热带亚热带果树以及热作等的生产基地，在农业生产上具有举足轻重的地位．但由于大部分坡耕地是顺坡开垦，重用轻养，耕作粗放，少施肥等，以致存在土壤有机质偏低，氮、磷、钾养分贫乏，土壤酸度大，耕层浅薄，砂化严重，干旱，农作物产量低等问题。然而，坡耕地土层深厚，环境条件优越，水热充足，生产潜力大。针对坡耕地的这些状况，提出：搞好农地整治，变“三跑地”为“三保地”；用养结合，以地养地；因地制宜，合理利用；增施化学肥料，调节土壤养分等对策。     

环境哲学与历史性转变

所谓环境哲学，就是从哲学角度研究环境与发展这一矛盾的运动规律，并用以指导环境工作实践的一门科学。从哲学角度看，推行历史性转变首在转变那些不适应客观变化的观念、经验和制度，以实践作为检验真理的唯一标准，对受计划经济体制影响的理念和经验进行反思，走出误区，以利转变。环境与经济的“并重”和“同步”是促进环境与发展矛盾转化的根本途径，“综合”是用改革的方法解决发展中的环境问题，是实现前两个转变的基本保障。总之，实施“三个转变”就是发挥人的主观能动作用，积极创造条件，促使环境与发展的矛盾由“两难”向“双赢”转化，将“以牺牲环境换取经济增长”转变为“以保护环境，优化经济增长”，真正走上生产发展、生活富裕、生态良好的文明发展道路。     

隆回县高海拔山区高效生态经济型退耕还林造林模式研究

通过对六种植物配置方式及三种开发模式的对比试验分析，试验出了一种融水土保持效益与经济效益于一体的高效生态经济型造林模式，并探讨了灰毡毛忍冬产量与海拔高度的关系．结果表明：在自然条件恶劣的小沙江高海拔山区，采用金银花(品种为灰毡毛忍冬) 三木药材或其它草本药材，运用景观生态学原理进行设计开发，可获得很好的经济效益与社会效益，并能保持山区的可持续发展．同时还试验出了主栽树种灰毡毛忍冬在海拔1000～1400m之间时经济效益最好．     

耕地土壤碳固存的措施与潜力

土壤CO2排放与土壤退化、土壤有机质(SOC)含量减少和土壤质量下降密切相关。耕地具有较大的碳固存潜力。通过采用最佳管理措施(BMPs)和进行土壤修复来提高土壤质量，能增加SOC含量和提高土壤生产力，并能部分起到减缓温室效应的作用。文章从土壤固碳的机制入手，系统总结了在耕作土壤碳固存方面的研究。从土壤侵蚀控制、退化土壤修复、保护性耕作、残落物管理，改善农作物制度等方面，论述了耕地的固碳潜力，并提出了一系列实现碳固存的措施。最后估算出耕地土壤总的固碳潜力为0．73～0．87Pg/a。研究表明,在替代性能源开发之前，耕地碳固存是一项切实可行的措施。     

A PROPOSED METHOD OF EVALUATING FLOOD DAMAGES TO HISTORIC HOMES - AN EXTERNALITY APPROACH1

ABSTRACT: Traditional procedures for evaluating flood damages to residential dwellings do not reflect intrinsic values when applied to historic homes. Such structures are worth more than that determined by using depth-damage curves provided by insurance companies who assess damage values based upon current labor and material costs. The evaluation of the worth of a historic home and subsequent damages due to inundation can be regarded as a problem of externalities. An assessment technique reflecting historic amenities or what has been termed replication cost is proposed in this paper. Replication costs would have widespread use not only in solving flood dammage problems, but also in any study where historic entities are subject to damages from catastrophies such as hurricanes, soil and beach erosion, and increasing urbanization. If adopted as a technique, it would enhance and preserve the ever-decreasing enclaves of historic homes and neighborhoods.     

历史街区旅游开发初探

在阐释历史街区内涵的基础上，研究了历史街区旅游开发的问题。通过分析历史街区旅游开发的必要性及可能带来的负面影响，依据历史街区的保护原则，借鉴国内外历史古城旅游利用的基本思路，提出了历史街区旅游开发的“主客相融”模式和“低密高质”模式。     

A Special Vegetation Index for the Weed Detection in Sensor Based Precision Agriculture

Many technologies in precision agriculture (PA) require image analysis and image- processing with weed and background differentiations. The detection of weeds on mulched cropland is one important image-processing task for sensor based precision herbicide applications. The article introduces a special vegetation index, the Difference Index with Red Threshold (DIRT), for the weed detection on mulched croplands. Experimental investigations in weed detection on mulched areas point out that the DIRT performs better than the Normalized Difference Vegetation Index (NDVI). The result of the evaluation with four different decision criteria indicate, that the new DIRT gives the highest reliability in weed/background differentiation on mulched areas. While using the same spectral bands (infrared and red) as the NDVI, the new DIRT is more suitable for weed detection than the other vegetation indices and requires only a small amount of additional calculation power. The new vegetation index DIRT was tested on mulched areas during automatic ratings with a special weed camera system. The test results compare the new DIRT and three other decision criteria: the difference between infrared and red intensity (Diff), the soil-adjusted quotient between infrared and red intensity (Quotient) and the NDVI. The decision criteria were compared with the definition of a worse case decision quality parameter Q, suitable for mulched croplands. Although this new index DIRT needs further testing, the index seems to be a good decision criterion for the weed detection on mulched areas and should also be useful for other image processing applications in precision agriculture. The weed detection hardware and the PC program for the weed image processing were developed with funds from the German Federal Ministry of Education and Research (BMBF).     

韧性城市视角下的历史街区防火韧性评估体系构建*

为提升历史街区的防火韧性,推进韧性城市的建设,采用PSR（压力-状态-响应）模型搭建3级评估框架;结合指标选取原则,从外部环境刺激、内部潜在风险、组成成分价值、组成成分特征、消防救灾能力、适应恢复力6个要素对评估指标进行筛选;运用专家打分法和层次分析法确定各项指标的权重,并构建由36个指标项组成的历史街区防火韧性评估体系及评估模型。结果表明:历史街区的防火韧性宜从系统面对火灾风险的压力、系统自身在受灾时的状态、灾后系统做出的应急响应3个方面进行综合评估;该评估体系具有一定的可操作性和可推广性,既可为定量评估历史街区的消防能力提供参考依据,亦可为推进我国历史街区的保护和开发提供决策支持。