强度侵蚀红壤区不同治理措施对土壤理化性质的影响

为了探讨生态治理措施对强度侵蚀红壤区土壤质量的影响,2005年对治理区4种不同治理措施下土壤理化性状进行比较研究。结果表明:强度侵蚀红壤区经过5年治理后,土壤的理化性质有了明显的改善。封禁措施改善土壤的物理性状最明显,生态果园措施次之,种植胡枝子最差。全面播种百喜草和封育措施能显著改善土壤的化学性状,生态果园措施略差,种植胡枝子改善作用并不明显。同时,这些措施的效果离原始林区的土壤质量还有很大差距。     

长汀县水土保持监测实践与探讨

长汀县是我国南方最严重的花岗岩水土流失区之一,其水土流失类型在南方花岗岩红壤侵蚀区具有典型的代表性。2000年成立长汀县水保监测站以来,先后布设了1个气象观测哨4、个水蚀控制站、29个天然降雨径流小区1、18个固定监测样地,初步形成了监测网络并取得了监测成果。     

Soybean glycinin subunits: Characterization of physicochemical and adhesion properties

Soybean proteins have shown great potential for applications as renewable and environmentally friendly adhesives. The objective of this work was to study physicochemical and adhesion properties of soy glycinin subunits. Soybean glycinin was extracted from soybean flour and then fractionated into acidic and basic subunits with an estimated purity of 90 and 85%, respectively. Amino acid composition of glycinin subunits was determined. The high hydrophobic amino acid content is a major contributor to the solubility behavior and water resistance of the basic subunits. Acidic subunits and glycinin had similar solubility profiles, showing more than 80% solubility at pH 2.0-4.0 or 6.5-12.0, whereas basic subunits had considerably lower solubility with the minimum at pH 4.5-8.0. Thermal analysis using a differential scanning calorimeter suggested that basic subunits form new oligomeric structures with higher thermal stability than glycinin but no highly ordered structures present in isolated acidic subunits. The wet strength of basic subunits was 160% more than that of acidic subunits prepared at their respective isoelectric points (pI) and cured at 130 degrees C. Both pH and the curing temperature significantly affected adhesive performance. High-adhesion water resistance was usually observed for adhesives from protein prepared at their pI values and cured at elevated temperatures. Basic subunits are responsible for the water resistance of glycinin and are a good starting material for the development of water-resistant adhesives.     

淮河上游全新世黄土-古土壤序列元素地球化学特性研究

在野外考察研究的基础上,对河南禹州全新世风成黄土-古土壤剖面系统采样,利用X-荧光光谱仪测定了常量元素和微量元素的含量及其变化,并与磁化率曲线、粒度变化曲线对比分析发现:常量元素氧化物比值钾钠比、残积系数和以Rb为代表的微量元素含量等随剖面层次呈规律性变化,即在古土壤层(S0)中含量最高,表土层(MS)中次之,在黄土层(L1、Lt、L0)中最低。硅铝率和Sr的含量表现出相反的变化规律。表明在全新世古土壤层和表土层形成时期,气候温暖湿润,成壤作用和次生粘化作用较强;在黄土堆积时期,气候比较干旱,沙尘暴频繁,成壤作用微弱。这些化学参数与磁化率曲线可以进行对比,表明成土过程中元素的迁移变化受全新世以来气候变化和成壤环境变化的控制。与黄土高原腹地的洛川剖面相比,淮河上游禹州剖面中绝大多数常量元素的含量较高,而绝大多数微量元素的含量偏低,磁化率也显著偏低,绝对值差别很大,粒度组成当中细沙成分含量很高,这说明淮河上游黄土物质来源与黄土高原地区明显不同。联系全新世时期黄河频繁泛滥、改道、沉积与黄淮平原盛行东北风形成流沙地的事实,认为淮河上游的黄土是黄河泛滥沉积物质经过风沙活动改造,由东北风力系统搬运而来的近源粉尘堆积,再经过就地风化或者成土改造而形成。     

Fractal features of soil particle size distribution and the implication for indicating desertification

Some of the effects of land desertification on soil properties are manifested by the coarsening of the soil particlesize distribution (PSD) and the losses in organic C and nutrients. The changes and characteristics of PSD and selected chemical properties in soils at the 0-15 cm plough layer from different degrees of desertified croplands are analyzed in the semiarid Horqin Sandy Land, northern China. The fractal dimension of the PSD is emanated to characterize the patterns of PSD. The relationships between the fractal dimension of the PSD and selected soil properties are discussed. The results show that: (1) in the transformation from potential desertified cropland to extremely desertified cropland, the sand content at the 0-15 cm soil increased from 69% to 93%, organic C and total N contents decreased by 65% and 69%, respectively; (2) the fractal dimension of PSD ranged from 2.179 to 2.611, the more the contents of sand, the lower the fractal dimension and the higher the desertified degree of farmland. In the desertification process within the studied area, the mean fractal dimension decreased from 2.555 for the potential desertified soils to 2.298 for extremely desertified soils; (3) there existed considerable linear relationships between fractal dimension and soil properties. It was shown that fractal dimensions of PSD are useful parameters able to monitor soil degradation and to estimate the degree of soil desertification.     

水分生态环境对刺槐细根垂直分布的影响

采用土钻法,对安塞县和长武县的刺槐细根面积垂直分布特征进行调查研究,结果表明:（1）刺槐细根的垂直分布与水分生态环境密切相关,现存的细根密度是对具体生境逐步适应调整的结果。（2）刺槐在遗传特性上表现为深根性树种。刺槐细根的垂直分布除了受树种遗传特性的影响,很大程度上受水分生态环境的影响。（3）刺槐细根的垂直分布区域与降雨的补偿深度基本一致,如果土壤中的水分得不到很好的补偿,将对刺槐的生长造成很大影响。因此,黄土高原营造人工林,应充分考虑降水对土壤含水量的补偿深度和补偿程度,以水分生态环境中所能容纳的适宜细根密度为依据确定造林密度,才能使树木达到最大生产力。     

农村社区动态交互式三维虚拟漫游系统的实现

为了提高农村社区规划建设的可视化宣传效果,为用户提供直观的操作工具辅助实现农村社区规划建设信息的管理,提出了一种基于虚拟建模现实语言(VRML)的农村社区动态交互三维虚拟漫游系统的实现方法.在本方法中,农村社区三维虚拟场景是通过社区布局VRML建模、社区纹理数据和层次化数字高程模型(DEM)数据的VRML表达两个过程建立;通过将社区中建筑物、树木等对象实体设置为具有三维坐标和属性集的锚点,并利用Java与虚拟现实建模语言对锚点的操作实现空间定位、距离分析、三维虚拟场景属性和空间位置查询等实时动态交互过程.该方法已经在北京房山八十亩地村网络虚拟漫游系统的实现中得到应用,应用效果表明系统仅需在带宽100 kB网络条件下即可快速响应用户的各种操作请求,适合在大都市周边农村地区大规模推广应用.     

种植水稻和长期施用无机肥对红壤氨氧化细菌多样性和硝化作用的影响

以中国科学院红壤生态试验站发育于第四纪红黏土的植稻红壤为研究对象,研究了长期种植水稻和施用无机肥对土壤β-变形杆菌纲中氨氧化细菌多样性和硝化作用的影响。原始红壤改种水稻13年后,氨氧化细菌16SrDNA的DGGE条带数量增加,条带谱与原始红壤的差异较大,相似性为61%,说明种植水稻后土壤氨氧化细菌群落结构发生了变化。PCR-DGGE方法研究结果也显示,长期施用无机氮肥的处理(NP、NPK和NK),DGGE带谱相似性较高,达到73%,硝化率和硝化势均高于未施用氮肥的处理。逐步回归分析显示硝化率和硝化势均随着土壤脲酶活性的提高而显著增加。推测尿素可提高土壤水解氮含量,使土壤脲酶活性提高,促进硝化细菌的生长,进而提高硝化率和硝化势。     

兔出血症病毒VP60主要抗原表位基因的克隆与序列分析

本实验用RHDV CD株人工感染家兔,发病死亡后,取肝脏匀浆,用Trizol试剂从匀浆上清中提取病毒RNA。根据Genbank已发表序列保守区设计并合成引物,采用RT—PCR方法扩增了RHDV衣壳蛋白VP60主要抗原表位基因。PCR产物纯化后,进行序列测定。测序结果表明,VP60主要抗原表位基因长525bp。该序列与已发表的其它13株RHDV VP60同一核苷酸序列及推导的氨基酸序列进行同源性比较。结果显示,CD株核酸序列与WX-84株同源性最高为97.5%,与其它毒株的同源性在92.0%~96.6%之间。氨基酸序列与WX-84株、墨西哥Mexico-89株同源性最高为99.4%,与其它毒株的同源性在96.6%~98.3%之间。     

惰性载体对玫烟色拟青霉产孢和孢子活力的影响

玫烟色拟青霉Paecilomyces fumosorose础地理分布广泛，昆虫寄主多样，能侵染多种昆虫，包括同翅目、鳞翅目、鞘翅目、膜翅目等，是一种重要的昆虫病原真菌。近年来国外有关其生物学、分类、生化和应用的研究报道显著增多，但国内研究较少。虽然该菌寄主广泛，但国内外对其研究主要作为粉虱、蚜虫等刺吸式口器害虫的微生物防治因子。在自然界致病的鳞翅目幼虫虫尸上分离到1株玫烟色拟青霉，其对蚜虫、粉虱等刺吸式口器害虫有较高毒力。本试验利用惰性载体辅以农（副）产品为材料，对其在不同载体上生长、产孢量及对分生孢子存活的影响进行研究，对于开发和利用这一生物防治资源具有较为重要的意义。