R0-代数与MV-代数的关系

证明了剩余格和正则剩余格中一些典型的附加条件之间的等价性,引入了正规剩余格的概念并给出了其若干性质。以此为基础,讨论了R0-代数和MV-代数之间的关系。     

区域经济发展的土地利用及生态安全管理——以宝鸡地区为例

区域社会经济发展与土地利用结构关系密切。文中采用耕地动态度、相对变化率、转移率、新增耕地率、线性回归分析以及洛伦兹曲线等方法,以宝鸡地区为例分析了土地动态变化以及与区域经济发展关系、耕地与粮食匹配关系。结果表明：市区和山区县土地变化率大,川原县区相对较小,耕地变化与经济发展呈高度负相关关系。面对区域经济发展中土地资源出...     

Changes in soil organic carbon and nitrogen after 26 years of farmland management on the Loess Plateau of China

Soil carbon(C) and nitrogen(N) play a crucial role in determining the soil and environmental quality. In this study, we investigated the effects of 26 years(from 1984 to 2010) of farmland management on soil organic carbon(SOC) and soil N in abandoned, wheat(Triticum aestivum L.) non-fertilized, wheat fertilized(mineral fertilizer and organic manure) and alfalfa(Medicago Sativa L.) non-fertilized treatments in a semi-arid region of the Loess Plateau, China. Our results showed that SOC and soil total N contents in the 0–20 cm soil layer increased by 4.29(24.4%) and 1.39 Mg/hm2(100%), respectively, after the conversion of farmland to alfalfa land. Compared to the wheat non-fertilized treatment, SOC and soil total N contents in the 0–20 cm soil layer increased by 4.64(26.4%) and 1.18 Mg/hm2(85.5%), respectively, in the wheat fertilized treatment. In addition, we found that the extents of changes in SOC, soil total N and mineral N depended on soil depth were greater in the upper soil layer(0–30 cm) than in the deeper soil layer(30–100 cm) in the alfalfa land or fertilizer-applied wheat land. Fertilizer applied to winter wheat could increase the accumulation rates of SOC and soil total N. SOC concentration had a significant positive correlation with soil total N concentration. Therefore, this study suggested that farmland management, e.g. the conversion of farmland to alfalfa forage land and fertilizer application, could promote the sequestrations of C and N in soils in semi-arid regions.     

基于GIS西北地区生态风险信息系统构建

西北地区生态环境极其脆弱,迫切需要利用地理信息系统(GIS)技术构建能够对该区生态风险信息进行快速、准确的评价系统,加之GIS技术在生态风险评价研究中的应用日益广泛,G IS具有强大的空间分析功能和海量数据管理优势。基于此,提出了基于G IS西北地区生态风险信息系统构建方案,阐述了系统开发的平台、系统目标及系统总体设计,分析系统的主要功能包括信息的输入、查询、空间操作与分析、风险评价模型及信息输出。     

Vertical Distribution and Seasonal Dynamics of Fine Root Parameters for Apple Trees of Different Ages on the Loess Plateau of China

The vertical distribution pattern and seasonal dynamics of fine root parameters for the apple trees of different ages （3, 10, 15, and 20 years old） on the Loess Plateau of China were studied. Soil coring method was used to determine the vertical distribution and seasonal dynamics of fine roots at different root radial distances （1.0, 1.5, and 2.0 m from the main tree trunk）. The fine root biomass density （FRD）, fine root length density （RLD）, and specific root length （SRL）, as well as soil water content and soil temperature were also measured. The FRD and RLD for the 10, 15, and 20 years old trees reached peak values in the 20-30 cm soil layer. For the 3 years old tree, the highest FRD and RLD were observed in the 10-20 cm soil layer. The FRD and RLD decreased with increased soil depth from the 10-20 or 20-30 cm soil layer for all age apple trees. The SRL declined with the increase of tree age. The FRD at the 1.0 m radial distance from the main tree trunk was higher than that at other radial distances in the 3 and 10 years old orchard. However, in the 15 and 20 years old orchards, especially the 20 years old orchard, the FRD at the 2.0 m radial distance was nearly equal to or higher than that at the 1.0 and 1.5 m radial distances. For all the root radiuses or the tree ages, the FRD, RLD, and SRL were the highest in spring and the lowest in autumn. The age of an apple tree does not affect the vertical distribution pattern but the biomass of fine roots and the SRL. Radial distance affects the root horizontal distribution of 3 and 10 years old trees but the 15 and 20 years old trees. Additionally, effects of soil temperature and soil moisture on fine root distribution or seasonal dynamics are not significant.     

区域地貌中的聚类分析及贝叶斯判别方法

为了对区域地貌的各项数据进行科学解读,以寻求建立区域地貌数字系统的方法与模式,利用系统聚类法对区域地貌进行了分类,并用贝叶斯判别法检验了分类的合理性,结果与用系统聚类法得到的分类一致,说明系统聚类法对区域地貌数据分析的结果是科学的。     

陕西省延川县孙家塬经济林土壤水分和水分平衡

对陕西省延川县孙家塬枣树林和苹果林4m深度土层水分的变化进行了研究,并对土壤水分有效性、土壤干层及其水循环等方面进行了分析。结果表明,枣树林地含水量平均为10.6%,还有4.5%的土壤水资源可以利用。苹果林地4m深度范围内平均含水量为7.4%,2.0—4.0m深度范围内土壤水资源基本耗尽。苹果林地土壤含水量自上向下呈现高—低—高分层变化特点,枣树林地土壤水分剖面垂向分层不明显。枣树林地和苹果林地土壤水分基本都呈难效水状态,但枣树林土壤水分接近中效水,土壤水分对苹果林生长具有严重的抑制作用,对枣树林的生长基本没有抑制作用。枣树林地2.0—4.0m深度范围仅有轻度干层发育,苹果林地土层2.0—4.0m深度范围有轻度干层、中度干层和重度干层发育。苹果林地和枣树林地土壤干层切断了深层水分与上层的联系。水循环主要表现为地表水循环,基本不存在地下水循环,形成了土壤—植物—大气的水分循环模式,属于异常水分循环类型。干层长期发展会导致该区地下水位的持续下降和地下水资源减少。该区土壤水分条件更适于发展枣树经济林。     

陕西省耕地数量变化对粮食总产的影响

对1978年以来陕西省粮食总产量、耕地面积的变化以及相关影响因素进行统计分析,结果表明,陕西省耕地资源数量呈持续减少趋势,其主要原因是生态退耕和农业产业结构调整,其次为建设用地、灾毁等;粮食总产量呈波动上升趋势 ,粮食总量年变化率与粮食播种面积年变化率、耕地面积减少量和因其导致的粮食减产量变化趋势高度一致,说明耕地面积的减少直接导致粮食产量的减少,耕地资源数量是影响陕西省粮食产量的重要因素.因此,保持一定数量的耕地面积的动态平衡是保障粮食安全的先决条件.     

Meyer-Konig and Zeller算子及Bernstein算子在内插空间中的逼近

给出了一般内插空间中线性一致有界算子序列逼近的正逆定理 ,作为应用 ,用 Meyer- Konig and Zeller算子和 Bernstein算子给出了一类特殊的内插空间中一致逼近的特征性定理 ,其结果为已有的经典 Zygmund类中相应结论的推广。     

户县秦岭山前冲积平原区生态环境调查

通过对户县秦岭山前冲击平原区生态环境的系统调查,认为该区生态环境的演变深深地打上了人类活动的印痕。建国以来经历了1996年以前的田园风光时期,"文革"过程中的生态环境退化及商品经济大潮下的环境恶化三个发展阶段。生态环境的恶化固然有自然演变的因素存在,但是,个人行为,尤其是政府行为主导的不合理地开发活动是导致生态环境恶化的主要因素。