Long-term gravel–sand mulch affects soil physicochemical properties,microbial biomass and enzyme activities in the semi-arid Loess Plateau of North-western China

The use of gravel–sand mulch is a traditional water-conservation technique in the semi-arid Loess Plateau of North-western China. In this study, we investigated the 16-year effects of this mulch on soil physicochemical properties (total organic C, N and P; bulk density; Ca, Cu, Fe, Mg, Mn and Zn; soil texture; pH), microbial biomass C, N and P and enzymatic activities (peroxidase, dehydrogenase, invertase, β-glucosidase, alkaline phosphomonoesterase and urease) in a field trial in China's Gaolan County. We examined how these parameters changed after 7, 11 and 16 years of mulching. After 16 years, soil bulk density and sand content increased significantly. Soil Ca and Cu contents did not change significantly during the study period, but Fe, Mg, Mn and Zn contents all decreased significantly after 16 years. The total N increased significantly after 11 years, but total C and N both decreased dramatically and significantly after 16 years (by 22% and 13%, respectively, compared to the control). The mulch significantly increased microbial biomass C (by 29% after 11 years), with similar results for N and P, but these positive effects were lost after 16 years. Enzyme activities revealed changes in the soil microbial community over time; the mulch increased enzyme activities until 11 years, followed by a significant decrease that suggested degradation of soil quality after long-term mulching. The positive effects of the mulch (increasing soil temperature) could explain the high microbial biomass and enzyme activities after 11 years. However, long-term increases in soil bulk density and sand content (caused by mixing of the mulch layer with the surface soil) and a lack of inputs of organic matter (caused by the barrier created by the mulch layer) led to degradation of the soil after 16 years.     

Experimental Analysis of the Water Weaken Effect on Gravel Soil Roadbed Locating in the Reservoir Region with Different Compactedness

It is vital to get the accurate data of the shear strength parameters of gravel soil with different water content and compactedness before they conduct the stability analysis for gravel soil roadbed. Under several test conditions, a series of direct shear tests were performed by using some gravel soil samples obtained from a selected roadbed which is under the influence of water level fluctuation. The corresponding results show that the gravel soil cohesion increased as the water content of fine soil increases till it meets its peak value, then it will decrease as the water content keeps increase. However, the internal friction angle will decrease slowly with the increase of water content of fine soil in the initial phase, and then it will decrease rapidly as the water content keeps increase. And on the other hand, the fitted shear strength parameters calculated from the test data has been influenced by the pre-load values that used to prepare soil samples, especially for the condition that the pre-load value less than the normal stress value applied in the direct shear test. All in all, the fitted shear parameters will be controlled by the relationship among water content, pre-load value and normal stress.     

烤烟专业化分级散叶收购存在问题及对策(英文)

针对散叶收购存在的问题,通过完善散叶收购设施建设,创新散叶收购管理模式,大抓专业化服务及烟叶分级培训,狠抓散叶收购等级质量管理,不仅有效减少了烟农的用工,也减轻了行业的存储、保管工作压力,同时提高了烟叶等级质量。     

基于多指标分析和分形维数的不同种植年限压砂地基质流与优先流特征研究

为明晰不同种植年限压砂地土壤优先流和基质流状况、改善区域水分生态环境,以宁夏不同种植年限(2、5、10、20、30 a和40 a)压砂地为研究对象,通过野外染色示踪试验,结合形态学、多指标分析及分形理论对不同年限压砂地土壤优先流和基质流特征进行分析.结果表明:随种植年限增长,土壤容重显著增大(P<0.05),饱和导水率...     

泥石流堆积物粒度分形特征及影响因素分析

汶川地震诱发了大量的泥石流,给山区带来了巨大的人员伤亡及财产损失,为了更好地对泥石流特征进行研究并对其危险性进行预测,通过野外取样对泥石流堆积物进行了粒度分析,并对汶川地震灾区泥石流堆积物的分形结构特征以及泥石流物源区岩性、松散物质量及沟道坡降对泥石流堆积物颗粒组成的影响进行了分析。结果表明,其粒度分维值介于2～3之间,平均值为2.49,标准差为0.19,分维值的离散度比较低。粉砂岩的分维值最小,其次是砂岩和泥灰岩;石英闪长岩的分维值最大,其次为石灰岩。分维值的变化趋势与松散物质量的变化趋势极为相似,分维值随着松散物质量的增大而增大。泥石流堆积物的分维还受到沟道坡降的影响,在其它影响因素相同的情况下,分维值随着沟道坡降的增大而增大。地震后泥石流堆积物的分形特征体现了泥石流危险度的大小,可为泥石流活动特征及危险性预测提供依据。     

茯茶“散茶发花”加工过程中茶多酚和碳水化合物及冠突散囊菌数量的变化研究

为探明“散茶发花”技术在不同嫩度茶叶原料上的发花情况及发花对各茶叶原料带来的影响,采用2008年一品茯砖茶原料(A)、2008年金湘益茯砖茶原料(B)、边销茶原料(C)以及2008年金湘益茯砖茶原料“快速醇化”后的成品(D)作为“散茶发花”加工原料,考察发花过程中主要生化成分及“发花”特征性微生物--冠突散囊菌数量的变化。结果表明,4种茶叶中的茶多酚、儿茶素、黄酮类、可溶性糖、粗纤维等的含量均有不同程度的下降;多糖的含量有小幅度的增加;在5天的发花期间,冠突散囊菌繁殖增长较快,第3天进入对数生长期,随后增长速率逐渐放缓直至发花结束。4种茯茶成品较其对应原料品质均有改善,加工过程中冠突散囊菌参与生化成分复杂的变化为品质的改善奠定了基础。     

季节冻土区路基冻胀翻浆防治措施试验研究

根据位于青海省109国道橡皮山试验段所观测的温度及水分数据,系统分析了传统砂砾垫层路基与隔水土工膜加碎石垫层路基在外界气候环境作用下,路基内各个观测位置温度与水分的变化以及造成这些变化的原因.比较了两个断面下路基各个观测位置的水分变化率的差异以及造成这些差异的原因,分析了这些差异对路基冻胀翻浆的影响.研究结果表明,在橡...     

基于Jensen模型的压砂地西瓜灌溉制度优化研究

针对压砂地西瓜水资源高效利用和合理灌溉制度问题,于2008年和2009年采用试坑对比试验方法进行了研究,利用水分生产函数Jensen模型分析了压砂地西瓜耗水规律及需水关键期,并用Jensen模型对压砂地西瓜灌溉制度进行了优化,结果表明:(1)压砂地西瓜全生育期耗水量为79.6~409.9 mm;(2)西瓜需水关键生育阶段顺序为"苗期开花坐果期膨大初期膨大中期伸蔓期膨大后期";(3)压砂地西瓜各生育阶段的水分敏感系数λ_1=0.6171,λ_2=0.2707,λ_3=0.0355,λ_4=0.1097,λ_5=0.1390,λ_6=0.1106;(4)通过灌溉制度优化发现:供水量范围为80~240 mm时增产效果最明显,供水量达到320 mm时,压砂地西瓜可获得高产。最优灌溉制度为:苗期灌水20~30 mm,伸蔓期灌水50~55 mm,开花坐果期灌水40~45 mm,膨大初期灌水70 mm,膨大中期灌水60~70mm,膨大末期灌水60~65 mm。     

赛尔矿区松散泥岩巷道支护技术研究

针对赛尔三矿巷道围岩松散、水化风化影响严重的问题,分析了巷道原支护方案存在的问题及影响巷道围岩稳定的主要因素,运用理论分析和数值模拟等手段优化了巷道支护参数,设计了不同围岩条件下的巷道支护方案。现场监测表明,采用优化的支护方案后,巷道表面位移大幅下降,巷道围岩稳定性有了明显提高,巷道支护效果良好。     

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay,China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of γ-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.