黄河中游的侵蚀环境与植被恢复前景

黄土高原的土壤侵蚀和生态环境问题世界瞩目。在保证蓄水拦沙效益基础上,提高林、草保存率,使植被恢复得到最佳的生态效益,是黄土高原环境整治中亟待解决的关键问题。本文根据黄土高原不同空间地理位置的流域、重点县水文监测资料,研究了气候、地表覆被、土地利用方式的变化对流域侵蚀产沙的影响以及流域产沙与地理环境要素间的耦合关系,定量分析了黄土高原,特别是多沙粗沙区自然与人文要素对流域侵蚀产沙的综合影响和因子的权重分析,并利用天然降雨植被生态需水适宜性系数和林、草恢复度的概念,重点探讨了黄河中游主要产沙区、尤其是多沙粗沙区退耕还林等土地利用方式宏观格局变化与植被恢复前景。研究表明,在植被生长主要依赖天然降雨的黄土高原,生物措施(植被类型)要与自然带相适应,应根据植被恢复度和植被生态需水适应性系数来进行宏观植被的恢复与实施。这是目前在不断增长的人口压力下,进行水土保持,解决好经济发展与环境保护、减少垦殖率与保证老百姓的基本农田、造林种草与植被类型的自然适应性、以及控制泥沙作用中生物措施与工程措施合理布局等诸多矛盾的关键所在。     

中国人文地理学概论教材评价与建设献议

笔者选取国内流行的几本人文地理学概论教材,对教材的内容、组织结构、表现形式、地图使用等方面进行较详细的评述,指出了存在的不足,在此基础上结合以往的研究及美国人文地理学概论教材的长处,提出新世纪中国此类教材建设的总体构想和若干具体编写建议。     

飞机人工增雨作业的决策方法

利用中尺度模式计算云中的宏观物理特征量,结合分析作物生育期内不同时段降水对产量的影响程度及其变化特征,计算了不同区域逐旬每毫米增雨对作物经济效益的影响。提出用冰面饱和、水汽垂直输送、水汽积分量等云的宏观指标和各主要农作物不同生育阶段增雨的潜在经济效益指标等共同确定播云作业区的决策方法。在山东省人工增雨业务技术系统实践中,完成作业时间、作业高度和作业区范围的决策过程。     

海洋磁场重力场信息系统建设

在简要介绍海洋磁场重力场探测技术发展概况的基础上,详细论述了海洋磁场重力场信息数据库的建设情况及数据管理系统、数据分析应用系统的功能组成,系统功能测试情况以及系统建设过程中取得的主要技术创新点,对该系统投入应用前的优化完善工作提出了建议。     

Spatial discretization of large watersheds and its influence on the estimation of hillslope sediment yield

The combined use of water erosion models and geographic information systems has facilitated soil loss estimation at the watershed scale. Tools such as the Geo‐spatial interface for the Water Erosion Prediction Project (GeoWEPP) model provide a convenient spatially distributed soil loss estimate but require discretization to identify hillslopes and channels. In GeoWEPP, the TOpographic PArameteriZation (TOPAZ) model is used as an automated procedure to extract a watershed boundary, hillslopes and channels from a digital elevation model (DEM). Previous studies in small watersheds have shown that the size of the hillslopes and the channel distribution affect the model estimates, but in large watersheds, the effects on the soil loss estimates have yet to be tested. Therefore, the objective of this study was to evaluate the effect of discretization on the hillslope sediment yield estimates using GeoWEPP in two large watersheds (>10 km²). The watersheds were selected and discretized varying the TOPAZ parameters [critical source area (CSA) and minimum source channel length (MSCL)] in a 30‐m resolution digital elevation model. The drainage networks built with TOPAZ were compared with each other using the drainage density index. The results showed that the discretization affected hillslope sediment yield estimates and their spatial distribution more than the total runoff. The drainage density index and the hillslope sediment yield were proportional but inversely related; thus, soil loss estimates were highly affected by the spatial discretization. As a result of this analysis, a method to choose the CSA and MSCL values that generates the greatest fraction of hillslopes having profile lengths less than 200 m was developed. This slope length condition is particularly crucial when using the WEPP and GeoWEPP models, in order for them to produce realistic estimates of sheet and rill erosion. Finally, and as a result of this analysis, a more reliable method was developed for selecting the TOPAZ channel network parameters (CSA and MSCL). Copyright © 2015 John Wiley & Sons, Ltd.     

雷州半岛甘蔗的营养状况

通过对雷州半岛蔗区甘蔗营养状况的普查 ,利用数理统计方法 ,分析了养分间、养分与经济性状间的相关关系。结果表明 :增N、提高土壤pH值可显著提高茎长 ,茎长的提高可促进单茎重、工业蔗产量、含糖量极显著提高。增K、Mg可显著提高有效茎 ,有效茎的提高可促进工业蔗产量显著提高 ,却导致锤度显著下降。偏施Mg会导致锤度极显著下降。因而采取的措施为增N、K ,合理配施镁含量低的石灰和P肥 ,以促进茎长、单茎重、有效茎的提高 ,从而提高产量 ;控施Mg肥 ,达到提高糖分含量的目的     

长江三峡香溪—莲沱段水土流失的研究

长江三峡香溪—莲沱段的水土流失可分为水蚀与重力侵蚀两类。据诸多自然地理因素的定量指标与产沙模数的关系,建立了产沙模数的经验公式[即式(1)],用式(1)计算出区内产沙量。据历史记载资料与地质地貌调查,探讨了区内新滩与链子崖的巨型崩塌-滑坡的成因与发展。在此基础上,研究了区内水土流失对自然环境及三峡工程的影响。     

Study on model for remote sensing estimation of maize yield

Through analysis of perpendicular vegetation index (PVI) from combination of visible and near-infrared spectrums reflecting the feature of crop reflectance, we come to the conclusion that the index can better indicate crop instantaneous photosynthesis whereas people generally regard it as the representation of crop leaf area index (LAI). Exploration of crop photosynthesis within a day and its period of duration leads to production of photosynthetic vegetation index (PST) that can reflect the whole crop accumulated photosynthesis, which means the total biomass produced by crop, moreover the method simulating PST is put forward by employment of multi-temporal spectrum parameters. On the basis of the achievements mentioned above, a new comprehensive model for remote sensing estimation of maize yield is established, which can comprehensively show major physiological actions of maize and the course of its yield formation, organically integrate various effective ways of crop yield estimation. It lays a solid foundation for carrying out remote sensing estimation of maize yield on a large scale.     

水稻单产遥感估测建模研究

本文系统扼要地总结了统计、气象、农学和光谱等估产模型,以及水稻遥感估产农学机理等主要研究结果,并在建立的多种估产模型中,重点介绍了具有应用前景的光谱估产与水稻生长模拟估产的复合模型。     

框架结构抗震可靠度优化的模型和准则

本以框架结构为研究对象,建议了一个用于结构抗震可靠度优化的模型,把最优结构表达为在给定的材料质量上限值和构件截面尺寸下限值的约束条件下具有最小地震失效概率的结构,模型中的约束函数全部都是设计变量的线性函数,可行域是一个凸域,采用Ｋｕｈｎ－Ｔｕｃｋｅｒ条件推地了最优解必须满足的准则,据此可以构造出优化的迭代格式,中讨论了优化准则的物理意义,给出目标函数对设计变量偏导数的解析求解过程。