岷江干旱河谷典型阳坡土壤质量动态与评估

横断山区干旱河谷地区的土壤是制约植被恢复的一个关键要素，但干旱条件下土壤质量与动态演变状况并不清楚，本研究以岷江干旱河谷核心地段的土壤为对象，研究了阳坡褐土土壤的物理、化学以及生物学特征在海拔梯度（1800m、2000m、2200m）格局及其时间动态（2005-2007）变化，应用主成分分析综合评价了土壤质量及其时空差异性，明确了土壤质量的变化趋势。主要研究结论如下： 1) 海拔梯度上土壤物理性状的变化，2005 年和2007 年土壤物理性状综合质量随着海拔的升高均得到了优化，即海拔2200 m＞海拔2000 m＞海拔1800 m。 2) 海拔梯度上土壤化学性质的变化，土壤化学综合性质2005 年随海拔升高而趋于变得更优，而2007 年海拔2000 m 最优，海拔1800 m 则最差。 3) 海拔梯度上土壤生物学性质的变化，2005 年土壤生物学性质随海拔升高表现出趋于更好，2007 年海拔2000 m 最优而海拔1800 m 地段最差。 4) 从土壤物理、化学、生物学三方面出发，应用主成分分析，分别分析得出2005 年和2007 年不同海拔高度的土壤质量综合得分。根据综合得分得出土壤质量综合评价的排列顺序为：2005 海拔2200 m＞2007 年海拔2000 m＞2005 年海拔2000 m＞2007 年海拔1800 m＞2007 海拔2200 m＞2005 年海拔1800 m。2005年土壤综合质量随海拔升高而趋好，2007 年则以海拔2000 m 最优，海拔1800 m和2200 m 差异不大。 5）排除人为干扰后，干旱河谷土壤物理性状在海拔1800 m 略有恢复，海拔2000 m 变化不明显，而海拔2200 m 仍有退化趋势；土壤化学性质在海拔1800 m和2000 m 地段得到恢复，而海拔2200 m 处仍有退化；土壤生物学性质在海拔2000 m 地段呈恢复趋势，而1800 m 和2200 m 仍处于退化状态。综合质量分析表明，与2005 年相比，2007 年海拔1800 m 和2000 m 地段土壤质量趋于变优而海拔2200 m 地段仍有退化迹象。 Soil is a key factor that affect the restoration of vegetation in the Hengduan Mountains dry valley area. But the dynamics and quality of soil is not knowed in dry area. In this study, soil physiochemical and biological characteristics ranging from 1800~2200m above sea level from a typical south-facing slope at the Minjiang River dry valley area had been studied, and characteristics of changes in soil quality along altitudinal gradients and time scales were also discussed. The principal component analysis was used to assess the soil quality. The main results were as follows: 1) Changes in soil physical properties along altitudes. Soil physical properties obtained the optimization along with the elevation in 2005 and 2007. 2) Changes in soil chemical properties. It was summarized that soil chemical properties increased with elevation in 2005, but the soil of 2000 m was the best in 2007. 3) Changes in soil biological characteristics. Soil biological properties increased with elevation in 2005, but the soil of 2000 m was the best and 1800 m was the worst in 2007. 4) Change tendency of soil quality. With the soil physics, chemistry and biology characteristics, we analysised the change tendency of soil quality in altitudes. The result indicated that soil quality increased with altituded in 2005, and soil quality of 2000 m was the best in 2007. 5) In brief, the soil quality is by physics, chemistry as well as the biology synthesizes the influence the final outcome. And the soil quality's change was manifested by soil physics, chemistry and the biology characteristics. All the results indicated soil quality still degenerated at 2200 m in in the dry valley of Minjiang River. And soil quality of 1800 m and 2000 m resumed slight.

夏季降水对青海湖水量平衡的影响

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陕北水蚀风蚀交错区两种生物结皮对土壤饱和导水率的影响

该文以陕北水蚀风蚀交错区普遍发育的地表和地上两种生物结皮为研究对象,分别以3种非生物结皮(无结皮、物理结皮、去除生物结皮)为对照,使用盘式入渗仪测定其饱和导水率。结果表明:与无结皮土壤相比,两种类型生物结皮均可极显著降低土壤饱和导水率;与去除生物结皮土壤相比,两种类型生物结皮对土壤饱和导水率的降低均不显著;与有物理结皮发育的土壤相比,地表生物结皮对土壤饱和导水率的降低不显著,而地上生物结皮对土壤饱和导水率的降低显著。一方面,两种生物结皮对土壤饱和导水率均有明显降低作用,预示生物结皮在降雨活动中可能会增加径流、降低入渗,阻碍研究区水分亏缺条件下的植被恢复和生态与环境建设。另一方面,与不同的对照相比,生物结皮对土壤饱和导水率的影响截然不同,该结论可在一定程度上解释当前有关生物结皮影响土壤水分入渗方面所存在的分歧。

密度对三种豆科牧草生产力和水分利用率的影响

研究播种密度对3种豆科牧草生产力和水分利用效率的影响,以探讨其在草地农业系统中的合理优化模式。结果表明:沙打旺(Astragelus adsurgens)在高密区第2年生产力最高(18321 kg.hm-2),第3年开始下滑;苜蓿(Medicago sativa)在中、高密区生产力的增幅和增量差别不显著,以第3年最高(22563和22108kg.hm-2);胡枝子(Lespedeza daurica)在中密区第3年最高(7856 kg.hm-2);加大密度使沙打旺提早进入生长盛期,第2年即达到高生产力和较高水分利用效率;苜蓿以中密区(20~30株/m2)效果最好;达乌里胡枝子的生产力和水分利用率偏低,在黄土塬区草地农业中没有优势。

区域可持续发展中生态足迹分析

以辽宁省2004～2008年统计数据为基础,应用生态足迹分析方法,计算了辽宁省2003～2007年的生态足迹和生态承载力。结果表明,辽宁省的人均生态足迹由2003年的2.5875hm2/人增加到2007年的3.3401hm2/人,而同期的人均生态承载力却由0.5652hm2/人降低到0.5590hm2/人,人均生态赤字则由2.0223hm2/人增长到2.7811hm2/人。高额的生态赤字反映出辽宁省人口对自然资源的利用已超出了生态承载力范围。生态赤字的快速增长则反映出当前的发展模式是不可持续的,生态环境处于不安全状态。通过对生态足迹的研究,提出发展中应调整产业结构,引进高新技术,改变生产和消费模式,以实现可持续发展。

Label free electrochemiluminescence protocol for sensitive DNA detection with a tris(2,2'-bipyridyl)ruthenium(II) modified electrode based on nucleic acid oxidation

Label free electrochemiluminescence (ECL) DNA detection based on catalytic guanine and adenine bases oxidation using tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] modified glassy carbon (GC) electrode was demonstrated in this work. The modified GC electrode was prepared by casting carbon nanotubes (CNT)/Nafion/Ru(bpy)(3)(2+) composite film on the electrode surface. ECL signals of doublestranded DNA and their thermally denatured counterparts can be distinctly discriminated using cyclic voltammetry (CV) with a low concentration (3.04 x 10(-8) mol/L for Salmon Testes-DNA). Most importantly, sensitive single-base mismatch detection of p53 gene sequence segment was realized with 3.93 x 10(-10) mol/L employing CV stimulation (ECL signal of C/A mismatched DNA oligonucleotides was 1.5-fold higher than that of fully base-paired DNA oligonucleotides). Label free, high sensitivity and simplicity for single-base mismatch discrimination were the main advantages of the present ECL technique for DNA detection over the traditional DNA sensors.

Tight intermolecular packing through supramolecular interactions in crystals of cyano substituted oligo(para-phenylene vinylene): a key factor for aggregation-induced emission

Strong supramolecular interactions, which induced tight packing and rigid molecules in crystals of cyano substituent oligo(para-phenylene vinylene) (CN-DPDSB), are the key factor for the high luminescence efficiency of its crystals; opposite to its isolated molecules in solution which have very low luminescence efficiency.

Potential energy landscape and robustness of a gene regulatory network: Toggle switch

Finding a multidimensional potential landscape is the key for addressing important global issues, such as the robustness of cellular networks. We have uncovered the underlying potential energy landscape of a simple gene regulatory network: a toggle switch. This was realized by explicitly constructing the steady state probability of the gene switch in the protein concentration space in the presence of the intrinsic statistical fluctuations due to the small number of proteins in the cell. We explored the global phase space for the system. We found that the protein synthesis rate and the unbinding rate of proteins to the gene were small relative to the protein degradation rate; the gene switch is monostable with only one stable basin of attraction. When both the protein synthesis rate and the unbinding rate of proteins to the gene are large compared with the protein degradation rate, two global basins of attraction emerge for a toggle switch. These basins correspond to the biologically stable functional states. The potential energy barrier between the two basins determines the time scale of conversion from one to the other. We found as the protein synthesis rate and protein unbinding rate to the gene relative to the protein degradation rate became larger, the potential energy barrier became larger. This also corresponded to systems with less noise or the fluctuations on the protein numbers.