Effect of Plant Roots on Penetrability and Anti-Scouri-bility of Red Soil Derived from Granite

Distribution of plant roots in a red soil derived from granite was investigated to study the effect of plantroots on intensifying soil penetrability and anti-scouribility by the double-cutting-ring and the undisturbedsoil-flume methods, respectively. The plant roots system consisting mostly of fibrils, < 1 mm in diameter,was mainly distributed in the upper surface soil 30 cm in depth. It can remarhably increase the penetrabilityand anti-scouribility of the red soil derived from granite. When the root density was > 0.35 root cm-2, theintensifying effect of roots on both the penetrability and the anti-scouribility could be described by exponentequations, △ Ks = 0.0021RD1.4826 (R2 = 0.9313) and △ As = 0.0003RD1.8478 (R2 = O.9619), where △ Ks isthe value of intensified soil penetrability, a As the value of intensified soil anti-scouribility and RD the rootdensity, especially in the top soils within 30 cm in depth where plant roots were conceotrated.

Soil anti-scourability enhanced by herbaceous species roots in a reservoir water level fluctuation zone

Revegetation is one of the successful approaches to soil consolidation and streambank protection in reservoir water level fluctuation zones(WLFZs).However,little research has been conducted to explore the impact of herbaceous species roots on soil anti-scourability during different growth stages and under different degrees of inundation in this zone.This study sampled two typical grasslands(Hemarthria compressa grassland and Xanthium sibiricum grassland)at two elevations(172 and 165 m a.s.l.)in the water level fluctuation zone(WLFZ)in the Three Gorges Reservoir(TGR)of China to quantify the changes in soil and root properties and their effects on soil anti-scourability.A simulated scouring experiment was conducted to test the soil anti-scourability in April and August of 2018.The results showed that the discrepancy in inundation duration and predominant herbaceous species was associated with a difference in root biomass between the two grasslands.The root weight density(RWD)values in the topsoil(0-10 cm)ranged from 7.31 to 13 mg cm^(-3) for the Hemarthria compressa grassland,while smaller values ranging from 0.48 to 8.61 mg cm^(-3) were observed for the Xanthium sibiricum grassland.In addition,the root biomass of the two herbs was significantly greater at 172 m a.s.l.than that at 165 m a.s.l.in the early recovery growth period(April).Both herbs can effectively improve the soil properties;the organic matter contents of the grasslands were 128.06%to 191.99%higher than that in the bare land(CK),while the increase in the water-stable aggregate ranged from 8.21%to 18.56%.Similarly,the topsoil antiscourability indices in both the herbaceous grasslands were larger than those in the CK.The correlation coefficients between the root length density(RLD),root surface area density(RSAD)and root volume density(RVD)of fine roots and the soil antiscourability index were 0.501,0.776 and 0.936,respectively.Moreover,the change in the soil antiscourability index was more sensitive to alternations in the RLD with diameters less than 0.5 mm.Overall,the present study showed that the perennial herbaceous(H.compressa)has great potential as a countermeasure to reduce or mitigate the impact of erosion in the WLFZ of the Three Gorges Reservoir.

Effect of Root Architecture on Structural Stability and Erodibility of Topsoils during Concentrated Flow in Hilly Loess Plateau

Traditional vegetation techniques for the control of concentrated flow erosion are widely recognized, whereas only a few studies have experimentally investigated the impacts of belowground roots on the erodibility of topsoils in semi-arid areas. To quantify the effects of root architectures on soil erodibility and its relevant structural properties, simulated flow experiments were conducted at six-week intervals from 18 July to 20 October in 2012 in the hilly Loess Plateau. Five treatments were: 1) bare(control), 2) purple alfalfa(Medicago sativa), representing tap roots(T), 3) switchgrass(Panicum virgatum), representing fibrous roots(F), 4) purple alfalfa and switchgrass, representing both tap and fibrous roots(T + F), and 5) natural recovery(N). For each treatment, soil structural properties and root characteristics were measured at an interval of six weeks. Soil anti-scouribility was calculated. Results showed that grass planting slightly reduced soil bulk density, but increased soil aggregate content by 19.1%, 10.6%, 28.5%, and 41.2% in the treatments T, F, T + F, and N, respectively. Soil shear strength(cohesion and angle of internal friction(φ)) significantly increased after the grass was planted. As roots grew, soil cohesion increased by 115.2%–135.5%, while soil disintegration rate decreased by 39.0%–58.1% in the 21 th week compared with the recorded value in the 9th week. Meanwhile, root density and root surface area density increased by 64.0%–104.7% and 75.9%–157.1%, respectively. No significant differences in soil anti-scouribility were observed between the treatments of T and F or of T + F and N, but the treatments of T + F and N performed more effectively than T or F treatment alone in retarding concentrated flow. Soil aggregation and root surface-area density explained the observed soil anti-scouribility during concentrated flow well for the different treatments. This result proved that the restoration of natural vegetation might be the most appropriate strategy in soil reinforcement in the hilly Loess Plateau.

Experimental Study on Engineering Behavior of Solidified Soil for Scour Repair and Protection

A new scour countermeasure using solidified slurry for offshore foundation has been proposed recently.Fluidized solidified slurry is pumped to seabed area around foundation for scour protection or pumped into the developed scour holes for scour repair as the fluidized material solidifies gradually.In the pumping operation and solidification,the engineering behaviors of solidified slurry require to be considered synthetically for the reliable application in scour repair and protection of ocean engineering such as the pumpability related flow value,flow diffusion behavior related rheological property,anti-scour performance related retention rate in solidification and bearing capacity related strength property after solidification.In this study,a series of laboratory tests are conducted to investigate the effects of mix proportion(initial water content and binder content)on the flow value,rheological properties,density,retention rate of solidified slurry and unconfined compressive strength(UCS).The results reveal that the flow value increases with the water content and decreases with the binder amount.All the solidified slurry exhibits Bingham plastic behavior when the shear rate is larger than 5 s^(-1).The Bingham model has been employed to fit the rheology test results,and empirical formulas for obtaining the density,yield stress and viscosity are established,providing scientific support for the numerical assessment of flow and diffusion of solidified slurry.Retention rate of solidified slurry decreases with the water flow velocity and flow value,which means the pumpability of solidified slurry is contrary to anti-scour performance.The unconfined compressive strength after solidification reduces as the water content increases and binder content decreases.A design and application procedure of solidified soil for scour repair and protection is also proposed for engineering reference.

Evolution of soil DOM during thermal remediation below 100℃:concentration,spectral characteristics and complexation ability

The impact of thermal remediation on soil function has drawn increasing attention.So far,as the most active fraction of soil organic matter,the evolution of dissolved organic matter(DOM)during the thermal remediation lacks in-depth investigation,especially for the temperatures value below 100℃.In this study,a series of soil thermal treatment experiments was conducted at 30,60,and 90℃ during a 90-d period,where soil DOM concentration increased with heating temperature and duration.The molecular weight,functional groups content and aromaticity of DOM all decreased during the thermal treatment.The excitation-emission matrices(EEM)results suggested that humic acid-like substances transformed into fulvic acid-like substances(FIII/FV increased from 0.27 to 0.44)during the heating process,and five DOM components were further identified by EEM-PARAFAC.The change of DOM structures and components indicated the decline of DOM stability and hydrophilicity,and can potentially change the bioavailability and mobility.Elevated temperature also resulted in the decline of DOM complexation ability,which may be caused by the loss of binding sites due to the decrease of polar function groups,aromatic structures and hydrophilic components.This study provides valuable information about the evolution of DOM during thermal remediation,which would potentially change the fate of metal ions and the effectiveness of the post-treatment technologies in the treated region.

干湿循环作用下剑麻纤维加筋膨胀土的抗裂作用及影响因素

为研究干湿循环作用下纤维加筋膨胀土的抗裂效果,分别开展了素土和剑麻纤维加筋膨胀土的干湿循环试验,并采用图像处理技术提取试样表面裂隙参数,分析了剑麻纤维含量及长度、干湿循环次数、试样含水率对裂隙发育的影响.结果表明:1)剑麻纤维加筋膨胀土具有较好的抗裂性能,且剑麻纤维的掺入对膨胀土的裂隙率和裂隙平均宽度影响较大,相较于素土试样,最优加筋土试样的裂隙率和裂隙平均宽度均比素土试样减小了约1/2.2)纤维长度相同时,随着纤维含量的增大,裂隙率、裂隙总长度、裂隙平均宽度和分形维数均呈先减小后增大的趋势,且纤维含量为0.4%时各参数值最小;纤维含量相同时,纤维长度对各裂隙参数影响不大.3)随着干湿循环次数的增加,加筋土和素土试样裂隙参数均呈逐渐增大趋势,但纤维加筋土裂隙率和裂隙平均宽度的增大幅度均比素土小;从第5次干湿循环开始,各裂隙参数增长趋缓.4)单次脱湿过程中,试样含水率由20%降至10%时,裂隙急剧发育,且素土裂隙的发育对含水率的变化更加敏感,含水率低于10%时,随着含水率的减小,试样裂隙率变小并趋于稳定;相同含水率条件下,剑麻纤维加筋土具有更好的抗裂性能.5)剑麻纤维加筋膨胀土的抗裂机理主要表现在两方面,一方面是剑麻纤维的掺入增大了膨胀土的渗透系数,促进了试样内水分的均匀分布,减小了试样各处的胀缩差异;另一方面纵横交错的剑麻纤维约束了聚集体之间大孔隙的收缩.

室内室外相结合教学模式在土壤学实验课程中的应用研究

为培养更多专业技术人才的需求,结合东北农业大学资源与环境学院现有条件和实际情况出发,利用室内与室外相结合的教学模式在土壤学实验课中进行认真的探索与实践。探索与实践过程中发现室内与室外相结合的教学模式可扎实巩固学生对每个实验内容与方法的理解与认知,提高学生理论与实践结合并进行计算的推理能力,提高学生自主创造能力进而增加对实验课程的学习兴趣和教学质量。

中国沙棘根际固氮菌的分离、鉴定及促生能力比较

【目的】对青海野生中国沙棘根际固氮菌进行分离、鉴定及促生能力比较,为挖掘具有潜在应用价值的根际促生菌提供依据。【方法】利用纯化培养方法从中国沙棘根际土中分离固氮菌;通过形态观察、生理生化检测和16S rDNA序列比对鉴定菌株;对固氮菌的解有机磷、解无机磷、解钾、固氮、种子萌发的能力进行测定;将固氮菌接种空心菜幼苗以验证其促生效果。【结果】鉴定出1株哈夫尼菌(N5)、1株不动杆菌(N6)、4株沙雷氏菌(N1、N2、N3、N4)。培养7 d后,6株固氮菌固氮透明圈直径与菌落直径的比值(D/d)为1.23~1.83,N3的D/d最大,较N5提高48.8%;培养3 d后,6株固氮菌溶解有机磷圈直径为6.43~9.65 mm,溶解无机磷圈直径为3.13~5.50 mm,解钾圈直径为8.18~22.17 mm。平板促生试验结果表明,固氮菌可提高空心菜种子萌芽率,并且可显著促进空心菜生长发育。其中,菌株N3和N6促生效果显著,其鲜质量分别为0.24 g和0.26 g,较对照组(CK)增加了33.3%和44.4%。【结论】固氮菌N3和N6分别为沙雷氏菌和不动杆菌,具有较强的解磷、解钾、固氮能力,且均能提高空心菜种子发芽率,促进空心菜幼苗生长发育。

芦苇根-土复合体抗剪性能与水陆交错带土壤质地的关系

[目的]了解湿地水陆交错带土壤质地对芦苇根—土复合体抗剪性能的影响及其相互之间的关系。[方法]以自然生长在闽江湿地水陆交错带不同质地土壤上的芦苇种群根系为研究对象,测定了芦苇根系的分布、形态及根—土复合体抗剪强度差异。结合土壤物理性质,采用灰色关联法与相关性分析对影响芦苇根—土复合体抗剪性能的因素进行分析。[结果](1)水陆交错带不同质地土壤物理性质差异明显,对芦苇根系的分布与形态产生了显著影响(P<0.05)。(2)水陆交错带不同质地土壤同一土层深度下,砂壤土与壤土黏聚力显著大于砂土(P<0.05),内摩擦角在不同质地土壤中差异不显著(P>0.05)。(3)通过灰色关联法分析发现,毛管孔隙度是影响芦苇根—土复合体黏聚力的最主要因素,灰色关联度为0.878;土壤含水量是影响芦苇根—土复合体内摩擦角的最主要因素,灰色关联度为0.921。(4)湿地水陆交错带砂壤土中芦苇根—土复合体抗剪性能最好,砂土中其抗剪性能最差。[结论]不同质地土壤中,芦苇根—土复合体抗剪性能差异明显。相较于砂土和壤土,密度小、含水量高和孔隙度大的砂壤土中芦苇根—土复合体抗剪性能最好。

聚丙烯酰胺对花岗岩砂土分离与产沙过程的影响

[目的]探究聚丙烯酰胺(PAM)施用对花岗岩母质发育砂土分离与产沙过程的影响,明确PAM改良砂土抗蚀性的浓度阈值,为崩岗侵蚀防治提供依据。[方法]选取崩岗侵蚀区花岗岩母质发育的砂土,设置5个PAM施入水平(0‰,1‰,3‰,5‰,7‰),通过径流冲刷模拟试验,研究不同水力条件下砂土产沙速率、分离速率及细沟可蚀性对PAM施用浓度的响应规律。[结果]①PAM显著降低了砂土的产沙速率、分离速率和细沟可蚀性,且显著提高了临界剪切力(p<0.01)。PAM的减沙效应随冲刷时间的增加呈降低后稳定的趋势,而随其施用浓度的增加逐渐增大。当PAM施用浓度在5‰以内时平均减沙效果最明显。②土壤分离速率与PAM施用浓度呈极显著的负相关关系(p<0.001),但随着PAM施用浓度的增加,分离速率的降低速率逐渐减缓,且PAM(F=37.39,p<0.001)对土壤分离与产沙过程的作用大于水流剪切力(F=15.38,p<0.001)。③PAM处理组与CK的细沟可蚀性之比与PAM浓度呈二次函数关系(R2=0.996,p<0.001),且5‰的PAM对细沟可蚀性的降低效率最显著。[结论]施用PAM有效降低了花岗岩砂土的产沙速率、分离速率与细沟可蚀性,提高了其临界剪切力,改良效果在PAM施用浓度低于5‰时呈不断增加的趋势,而PAM施用浓度大于5‰时改良效果没有明显变化。因此,建议5‰为PAM改良花岗岩砂土抗蚀性的浓度阈值。

乡村幼儿园教师学习力提升的困境及策略:基于辽宁省5县的调查

为了解乡村幼儿园教师学习力现状,分析当前乡村幼儿园教师学习力的现实困境,采用随机抽样方法对代表辽宁省不同经济发展水平的5个县域共1049名幼儿园教师发放自编问卷展开调查。结果发现,当前乡村幼儿园教师学习力在整体上处于中等水平,且不同职务和不同教龄的教师得分存在显著差异。各维度得分由高至低依次是学习互惠力、学习转化力、学习动力和学习反思力;而在这四个维度上,不同年龄、职务、教龄和婚姻状况的乡村幼儿园教师得分存在显著差异。据此,讨论并分析制约乡村幼儿园教师学习力发展的原因,并提出如下提升策略:调动学习主动性,践行终身学习理念;针对职业生涯阶段,抓住教师发展关键期;扩充学习资源,满足教师学习需求;增加培训机会,在实践中积累经验;利用乡村资源,激发教师乡土情怀。

Comparative Effects of Salt Stress and Extreme pH Stress Combined on Glycinebetaine Accumulation,Photosynthetic Abilities and Growth Characters of Two Rice Genotypes

Glycinebetaine （Glybet） accumulation, photosynthetic efficiency and growth performance in indica rice cultivated under salt stress and extreme pH stress were investigated. Betaine aldehyde dehydrogenase （BADH） activity and Glybet accumulation in the seedlings of salt-tolerant and salt-sensitive rice varieties grown under saline and acidic conditions peaked after treatment for 72 h and 96 h, respectively, and were higher than those grown under neutral pH and alkaline salt stress. A positive correlation was found between BADH activity and Glybet content in both salt-tolerant （P=0.71） and salt-sensitive （P=0.86） genotypes. The chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids contents in the stressed seedlings significantly decreased under both acidic and alkaline stresses, especially in the salt-sensitive genotype. Similarly, the maximum quantum yield of PSII （Fv/Fm）, photon yield of PSII （ФPSII）, non-photochemical quenching （NPQ） and net photosynthetic rate （Pn） in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and ФPSII, and Pn as well as Pn and leaf area in both salt-tolerant and salt-sensitive genotypes were found. Saline acidic and saline alkaline soils may play a key role affecting vegetative growth prior to the reproductive stage in rice plants.

EFFECTIVENESS OF PLANT ROOTS TO INCREASE THE ANTI-SCOURABILITY OF SOIL ON THE LOESS PLATEAU

The recent study results show that the intensification ability of plant roots to the anti-scourability of soil mainly depends on the distribution and twining of effective root density in the soil profile, and the physical basis of effective root density is the number of

Anti-scourability of purple soil on hillslopes with different land uses

A large-scale flume (40 cm×10 cm×10 cm) was used to determine soil anti-scourability of 4 different land uses of purple soil in hilly areas of Sichuan, China under artificial removal of vegetation to examine the effects of land uses on sediment production by runoff. The results showed that soil anti-scourability declined with the increase of slope gradients in the form of power function, but there was a significant difference in the effects of slope gradients on anti-scourability between different land uses. The ratio of the mean values of soil anti-scourability was 1︰2.2︰2.5︰3.6 for forest land, new waste pasture, old waste pasture, crop land respectively, indicating that forest and grass use can significantly improve soil anti-scourability. Compared with the observations from the runoff plots located at the same sites in this region, an inconsistent result was found between anti-scourability and anti-erodibility in hilly areas of Sichuan. Essential causes of the differences in soil anti-scourability were further discussed based on analyzing the influence of inherent soil characteristics induced by different land uses on soil anti-scourability.

A PRELIMINARY STUDY ON MECHANISM OF SOIL ANTI-SCOURABILITY ON THE LOESS PLATEAU

The resistance of soil to erosion by water can be classified into anti-washability and antiscourability. The former refers to the resistance of soil to dispersion and suspension caused by runoff, and the latter refers to the resistance of soil to mechanical disruption and the downward pushing caused by runoff. A systematic research on soil anti-scourability, however, is still lacking. The relationships between the anti-scourability, profile structure and physical properties of the soil on the Loess Plateau have been systematically studied in this note.

A STUDY ON THE RELATIONSHIP BETWEEN SPRING SOIL MOISTURE OVER CHINA AND EAST ASIA SUMMER MONSOON

The correlation analysis has been used to study the relationship between spring soil moisture over China and East Asian summer monsoon (EASM). It is shown that EASM has a strong positive correlation with spring soil moisture over southwest China and the Great Bend region of the Yellow River. A standard soil moisture index (SMI) has been defined using the observed soil moisture of the two regions. The results show that SMI has a strong correlation with EASM. The years of strong (weak) SMI are associated with stronger (weaker) summer monsoon circulation. In the years of strong SMI, the west Pacific subtropical high is much northward in position and weaker in intensity;the westerlies zone is also more to the north. All of these make EASM circulation move northward and cause the rainfall belt to relocate to North China and Northeast China. SMI can reflect the variation of the summer rainfall anomaly over eastern China. In the years of strong SMI, the rainfall belt is mainly located over the northern part of China. However, during the weak years, the summer rainfall belt is largely located over the mid-and lower-reaches of the Yangtze River. Additionally, the SMI has obvious oscillations of quasi 4-6 years and quasi 2 years. Moreover, negative SMI predicts EASM better than positive SMI.

Status and circulation characteristics of soil water in dryland field of southeast Shanxi Province

Based on the observed soil water data from experimental site located in southeast of Shanxi Province, the physical characteristics of soil water, crop effect on soil moisture, and the field water circulation pattern were studied by using the water balance method. The results suggested that soil water deficit often exists in fields of these areas. From May to June, the amount of water deficit in bare land rises to the maximum (232 8 mm) and falls to the minimum (66 6 mm) from August to September. By comparison, because of crop transpiration, both soil water deficit and dry soil layer in cultivated land are 15 1—40 4 mm more and 20—70 mm deeper respectively than those of bare land. Crops mainly planted in these areas have a relatively weak utilization ability to soil water. Winter wheat has the highest utilization ability to soil water among the crops planted in these areas. The soil water utilization ability of winter wheat is 26 2%—30 6% and winter wheat can use soil water that lies in soil layer below a depth of over 200 cm. Spring corn and millet can only consume soil water with the maximum ability of 13 4% and the deepest layer of 0—50 cm or 0—100cm, which shows that the soil water utilization ability of winter wheat is higher than that of spring crops. After crop is ripe, more than 41% of available soil water remains unused in field. So, increasing soil water storage and improving crop utilization ability to soil water by adopting efficient agrotechnique measures are the main ways for improving agricultural productivity in dry farming areas of Northern China.

Screening of cellulose decomposing fungi in sandy dune soil of Horqin Sandy Land

Cellulose decomposing fungi play an important role in litter decomposition and are decisive in nutrient cycling in sandy land ecosystems. Thirty-one strains were isolated to select efficient cellulose decomposers, and four efficient cellulose decomposing fungi （NM3-1, NM3-2, NM3-3, and NM3-4） were screened using a CMC （carboxymethyl cellulose） carbon source in dune soil of Horqin Sandy Land. They were identified as Asperigillus calidoustus, Fusarium oxysporum, Fusarium solani, and Hypocrea lixii by rDNA-ITS molecular biological methods. Cloth decomposition rates were 15.71%, 15.89%, 17.29%, and 17.89% by the four efficient decomposers incubated for 30 days, respectively. Screening of efficient cellulose decomposers can not only increase the dune soil functional microbe bank, but can also accelerate litter decom- position and available nutrient input in the Horqin Sandy Land.

A Systematic Study of Soil Collanses for Railway Slopes

A set of soil collapse prediction and prevention swtem for railway slopes is builtis this paper. Based on the field investisation, Oreen-Ampt model, the quantitytheory and computeraided decision-making sgutem, convereion tables ofworking rainfall ,grading tables of resistant ability to rainfall, and the warningrairifall levels are made, forming the chief part of a practical computer-aideddecisionmaking system. Usins the system, the danser degree of railway slopescan be predicted, and the reinforcins ensineerins and the flood control workcan also be arranged ratiofially.

信息获取对农户土壤保护外包行为的影响分析

基于河北、山东、江苏、安徽、江西以及湖北等6个粮食主产省的787户农户调研数据,利用Ordered Probit模型,分析了信息获取渠道与信息获取能力对农户土壤保护外包行为的影响。研究表明:第一,信息获取对农户的土壤保护外包行为具有显著影响,具体而言,信息获取渠道数量越多,农户土壤保护外包程度越高;信息获取能力对农户土壤保护外包行为的直接影响虽然并不显著,但能够强化信息获取渠道对农户土壤保护外包行为的积极影响。第二,尽管正式渠道与非正式渠道均能显著提高农户土壤保护外包程度,但仅正式渠道对农户土壤保护外包行为的作用受到信息获取能力显著的调节影响,非正式渠道对农户土壤保护外包行为的作用并未因信息获取能力水平的高低而产生明显变化。第三,信息获取对农户土壤保护外包行为的影响存在代际差异,对于决策者年龄较小的农户而言,正式渠道对其土壤保护外包行为的影响更大,而对于决策者年龄较大的农户来说,非正式渠道的影响更大,但正式渠道对不同年龄组农户的信息获取能力均有较高要求。基于此,提出以社会化服务的方式推动农户参与土壤保护应成为实施“藏粮于地”战略的重要举措之一,在此过程中需重视公共组织以及社会网络等不同类别信息传递渠道的建设,并加强农户信息获取能力培养,从而为农户参与土壤保护提供保障。