Shear resistance characteristics and influencing factors of root-soil composite on an alpine metal mine dump slope with different recovery periods

Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic changes and the influencing factors of the soil reinforcement effect of plant species after artificial vegetation restoration under different recovery periods.We selected dump areas of the Delni Copper Mine in Qinghai Province,China to study the relationship between the shear strength and the peak displacement of the root-soil composite on the slope during the recovery period,and the influence of the root traits and soil physical properties on the shear resistance characteristics of the root-soil composite via in situ direct shear tests.The results indicate that the shear strength and peak displacement of the rooted soil initially decreased and then increased with the increase of the recovery period.The shear strength of the rooted soil and the recovery period exhibited a quadratic function relationship.There is no significant function relationship between the peak displacement and the recovery period.Significant positive correlations(P<0.05)exists between the shear strength of the root-soil composite and the root biomass density,root volume density,and root area ratio,and they show significant linear correlations(P<0.05).There are no significant correlations(P>0.05)between the shear strength of the root-soil composite and the root length density,and the root volume ratio of the coarse roots to the fine roots.A significant negative linear correlation(P<0.05)exists between the peak displacement of the rooted soil and the coarse-grain content,but no significant correlations(P>0.05)with the root traits,other soil physical property indices(the moisture content and dry density of the soil),and slope gradient.The coarse-grain content is the main factor controlling the peak displacement of the rooted soil.

A PROPERTY OF HERMITE-PADE INTERPOLATION ON THE ROOTS OF UNITY

We extend a theorem of Ivanev and Saff to show that for the Hermite-Pade interpolant at the roots of unity to a function meromorphic in the unit disc, its leading coefficients vanish if and only if the corresponding interpolani to a related function vanishes at given points outside the unit disc. The result is then extended to simultaneous Hermite-Pade interpolation to a finite set of functions.

Soil physical properties and maize root growth under different tillage systems in the North China Plain

The standard cultivation system in the North China Plain is double cropping of winter wheat and summer maize. The main effects of this cultivation system on root development and yield are decreases in soil nutrient content and depth of the plow layer under either long-term no-tillage or rotary tillage before winter wheat sowing and no tillage before summer maize sowing. In this study, we investigated the combined effects of tillage practices before winter wheat and summer maize sowing on soil properties and root growth and distribution in summer maize. Zhengdan 958(ZD958) was used as experimental material, with three tillage treatments: rotary tillage before winter wheat sowing and no tillage before summer maize sowing(RTW + NTM), moldboard plowing before winter wheat sowing and no tillage before summer maize sowing(MPW + NTM), and moldboard plowing before winter wheat sowing and rotary tillage before summer maize sowing(MPW + RTM).Tillage practice showed a significant(P < 0.05) effect on grain yield of summer maize. Grain yields under MPW + RTM and MPW + NTM were 30.6% and 24.0% higher, respectively, than that under RTW + NTM. Soil bulk density and soil penetration resistance decreased among tillage systems in the order RTW + NTM > MPW + NTM > MPW + RTM. Soil bulk densities were 3.3% and 515% lower in MPW + NTM and MPW + RTM, respectively, than that in RTW + NTM, and soil penetration resistances were respectively 17.8% and 20.4% lower,across growth stages and soil depths. Root dry matter and root length density were highest under MPW + RTM, with the resulting increased root activity leading to a yield increase of summer maize. Thus the marked effects of moldboard plowing before winter-wheat sowing on root length density, soil penetration resistance, and soil bulk density may contribute to higher yield.

Soil fixation and erosion control by Haloxylon persicum roots in arid lands, Iran

Vegetation roots contribute to soil fixation and reinforcement, thus improving soil resistance against erosion. Generally, the amount of soil fixation presented by roots mainly depends on root density and tensile strength. In the present study, we conducted the research in order to further understand the biotechnical properties of Haloxylon persicum and also to quantify its role in increasing soil cohesion in arid lands of Iran. Ten H. persicum shrubs were randomly selected for root distribution and strength investigations, in which five samples were set on flat terrain and other five samples on a moderate slope terrain. The profile trench method was used to assess the root area ratio(RAR) as the index of root density and distribution. Two profiles were dug around each sample, up and downslope for sloped treatment and north and south sides for flat treatment. The results showed that RAR increased with increasing soil depth and significantly decreased in 40–50 cm layers of downhill(0.320%) and 50–60 cm for uphill(0.210%). The minimum values for the northward and southward profiles were 0.003% and 0.003%, respectively, while the maximum values were 0.260% and 0.040%, respectively. The relationship between the diameter of root samples and root tensile strength followed a negative power function, but tensile force increased with increasing root diameter following a positive power function. The pattern of increased cohesion changes in soil profile was relatively similar to RAR curves. The maximum increased cohesion due to the presence of roots in uphill and downhill sides were 0.470 and 1.400 kPa, respectively. In the flat treatment, the maximum increased cohesions were 0.570 and 0.610 kPa in northward and southward profiles, respectively. The analysis of variance showed that wind and slope induced stresses did not have any significant effect on the amount of increased cohesion of H. persicum. The findings served to develop knowledge about biotechnical properties of H. persicum root system that can assist in assessing the efficiency of afforestation and restoration measures for erosion control in arid lands.

Fine root morphology and soil properties under influence of different tree stands along an altitudinal climosequence in the Carpathian mountains

In an era of climate change, understanding the factors that impact root systems can improve our understanding of carbon cycling in forest ecosystems. The study objective was to determine the impact of climatic conditions on the biomass and morphology of roots of different tree species along an elevation gradient, and consequently on properties of montane forest soils. The study plots were established at three different elevations(600, 800 and1000 m a.s.l.) along a slope with an inclination of 15°. The research plots were located in a beech stand(Fagus sylvatica L.) and fir stand(Abies alba Mill.). Soil samples were collected from each study plot, for which basic physical and chemical properties were determined. Additionally, we determined the morphology, production and decomposition rate of fine roots. Our analyses confirmed the significance of climatic conditions in the formation of soil properties, in particular the amount of accumulated carbon and nitrogen content. A decrease of root biomass and reduced root growth were recorded with increasing elevation. The characteristics of roots were linked with the properties of the studied mountain soils, in particular p H, alkaline cation content and content of selected micronutrients. Limitation of root growth in higher elevations affected both study species. Additional research into the formation of tree root morphology is needed, especially in mountainous regions where changes may occur more dynamically. This will provide a better understanding of how stands can cope with different types of environmental stress.

Studying the mechanical properties of the soil-root interface using the pullout test method

It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.

Comparison of the rheological properties of four root canal sealers

The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method （ISO 6876）, and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer （Capseal） and three commercial root canal sealers （AH Plus, Sealapex and Pulp Canal Sealer EWT） were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method （n= 5） and their viscosities were measured using a strain-controlled rheometer （n=5）. The correlation between these two values was statistically analysed using Spearman＇s correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated （p= -0.8618）. The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order： AH Plus〈Sealapex〈Capseal （P〈0.05）. All of the tested root canal sealers showed characteristic time- and temperature-dependent changes in their rheological properties. The viscosities measured using the strain-controlled rheometer were more precise than the flowabilities measured using the simple press method, suggesting that the rheometer can accurately measure the rheological properties of root canal sealers.

Effects of loading rate on root pullout performance of two plants in the eastern Loess Plateau,China

Root pullout performance of plants is an important mechanical basis for soil reinforcement by plant roots in the semi-arid areas.Studies have shown that it is affected by plant factors(species,ages,root geometry,etc.)and soil factors(soil types,soil moisture,soil bulk densities,etc.).However,the effects of loading rates on root pullout performance are not well studied.To explore the mechanical interactions under different loading rates,we conducted pullout tests on Medicago sativa L.and Hippophae rhamnoides L.roots under five loading rates,i.e.,5,50,100,150,and 200 mm/min.In addition,tensile tests were conducted on the roots in diameters of 0.5-2.0 mm to compare the relationship between root tensile properties and root pullout properties.Results showed that two root failure modes,slippage and breakage,were observed during root pullout tests.All M.sativa roots were pulled out,while 72.2%of H.rhamnoides roots were broken.The maximum fracture diameter and fracture root length of H.rhamnoides were 1.22 mm and 7.44 cm under 100 mm/min loading rate,respectively.Root displacement values were 4.63%(±0.43%)and 8.91%(±0.52%)of the total root length for M.sativa and H.rhamnoides,respectively.The values of maximum pullout force were 14.6(±0.7)and 17.7(±1.8)N under 100 mm/min for M.sativa and H.rhamnoides,respectively.Values of the maximum pullout strength for M.sativa and H.rhamnoides were 38.38(±5.48)MPa under 150 mm/min and 12.47(±1.43)MPa under 100 mm/min,respectively.Root-soil friction coefficient under 100 mm/min was significantly larger than those under other loading rates for both the two species.Values of the maximum root pullout energy for M.sativa and H.rhamnoides were 87.83(±21.55)mm•N under 100 mm/min and 173.53(±38.53)mm•N under 200 mm/min,respectively.Root pullout force was significantly related to root diameter(P<0.01).Peak root pullout force was significantly affected by loading rates when the effect of root diameter was included(P<0.01),and vice versa.Except for the failure mode and peak pullout force,other pullout parameters,including root pullout strength,root displacement,root-soil friction coefficient,and root pullout energy were not significantly affected by loading rates(P>0.05).Root pullout strength was greater than root tensile strength for the two species.The results suggested that there was no need to deliberately control loading rate in root pullout tests in the semi-arid soil,and root pullout force and pullout strength could be better parameters for root reinforcement model compared with root tensile strength as root pullout force and pullout strength could more realistically reflect the working state of roots in the semi-arid soil.

Preparation and Performance of Pueraria lobata Root Powder/Polylactic Acid Composite Films

Petroleum-based materials,such as plastic,are characterized by adverse environmental pollution;as a result,researchers have sought alternative degradable plastics that are environmentally friendly,such as polylactic acid(PLA).PLA has shown great potential to replace petroleum-based plastics.In this study,seven different samples of unmodified Pueraria lobata root powder(PRP)with different contents(i.e.,0,5,10,15,20,25,and 30 wt%)and three different modified PRPs(i.e.,treated with NaOH,NaOH-KH-550,and Formic)were used to reinforce polylactic acid(PLA)via solution casting process.These prepared PRP/PLA composite films were characterized using SEM,FTIR,UV-visible spectra analysis,TG,DSC,weight loss measurement(wt%),and mechanical measurements.The results showed that the PRP modified with KH-550(PRPK)intensified the interaction in the interface region between the PRP and the PLA matrix,thus increasing the tensile strength(54.5 MPa),elongation at break(2.8%),and Young’s modulus(3310 MPa)of the PRPK/PLA biofilms.Contact angle measurement showed that the PRP treatments contributed to the hydrophobicity of films.The transparency of PRP-10/PLA film atλ_(800)was 11.09%,and its UVA and UVB transmittance were 3.28 and 1.16,respectively.After blending PLA with PRP,the PRP/PLA composite films exhibited excellent biodegradability.In summary,PRPK improved the mechanical properties of PLA and prevented the films from ultraviolet light,suggesting that PRPK-5/PLA film could be used as packaging materials.

压热及酶解脱支处理对莲藕淀粉品质的影响

淀粉是莲藕的主要成分。本研究通过压热处理、酶解脱支处理进行莲藕淀粉改性,并对其品质进行比较。结果发现:改性后莲藕淀粉中直链淀粉与碘结合能力显著增强,其中普鲁兰酶脱支处理莲藕淀粉(ELRS)的碘结合力最高,即可溶性直链淀粉含量最高;水合能力显著增强,其中压热法处理莲藕淀粉(HLRS)的持水性、持油性和膨胀度(21.766%)最高,析水率(14.300%)最低;压热后普鲁兰酶脱支处理莲藕淀粉(HELRS)的溶解度(63.555%)、透明度(0.717%)最高;改性后莲藕淀粉的糊化起始温度(T0)、热焓值(ΔH)、糊化温度(ΔT)均有所下降,其中HELRS的ΔH最低,表明改性后熔解莲藕淀粉所需的能量减少;检测改性后淀粉的凝胶特性表明,莲藕淀粉的硬度、弹性、内聚性、粘性和回弹性均有所下降。该研究结论为食品生产中针对不同需求进行淀粉改性提供了理论依据,并为莲藕淀粉的高附加值产品开发提供指导。

超声处理时间对莲藕淀粉理化和结构特性的影响

以莲藕淀粉(lotus root starch,LS)为对象,探究不同超声时间(0、10、20、30、40、50 min)对LS糊化特性、流变特性以及片层结构、结晶结构、短程有序结构、微观结构等的影响。结果表明,不同超声时间处理后LS分子链溶胀和缠结增加,糊化黏度最大增至(6059±31)mPa·s;淀粉颗粒表面出现裂缝、塌陷及坑洞,利于水分子进入,黏弹性增加。在超声作用下LS的α-1,6-糖苷键被破坏,部分支链断裂,形成淀粉短链,重新排列成有序的结构,短程有序结构增多,R_(1047/1022)值升高了3.20%;较短时间的超声处理(30 min)增强了淀粉分子间的相互作用,双螺旋结构变得有序和紧密,使T_p和ΔH值分别增大了11.09%和89.21%。长时间超声处理(40~50 min)不利于这种有序结构的形成。本研究结果可为超声技术在淀粉理化特性及多尺度结构调控中的应用提供理论参考。

玉米多品种间作对土壤团聚体组成和稳定性的影响

为阐明玉米多品种间作对土壤团聚体组成和稳定性的影响,通过为期2 a的田间试验,测定并分析了单品种单播(T1)、两品种间作(T2)、三品种间作(T3)和四品种间作(T4)下根质量密度(RMD)、根长密度(RLD)与土壤团聚体粒级和稳定性指标[大于0.25 mm粒径团聚体含量(R_(>0.25))、平均质量直径(MWD)、几何平均直径(GMD)]的变化规律。结果显示,与单品种单播相比,间作处理(T2~T4)的RMD、RLD、MWD、GMD、R_(>0.25)均呈递增趋势。与T1相比,T2、T3、T4处理的RMD分别显著(P<0.05)提高232%、657%、702%,RLD分别显著提高515%、1508%、1531%;干筛法测定的R_(>0.25)分别显著提高0.65、0.89、1.02百分点,MWD分别显著提高7.2%、10.7%、15.7%,GMD分别显著提高13.1%、21.1%、31.9%;湿筛法测定的R_(>0.25)分别显著提高4.34、9.42、11.81百分点,MWD分别显著提高19.6%、41.2%、54.9%,GMD分别显著提高27.0%、64.9%、87.8%。综上,玉米多品种间作可通过提高根质量密度和根长密度等根系特征,改善土壤团聚体的粒径分布及其稳定性。

羊粪对土壤性状及植物生长影响的研究进展

羊粪作为一种常见的热性肥料,富含氮、磷、钾等元素,可以改善土壤理化性状,并且通过土壤微生物与植物根际营养之间的互作促进作物生长,提高农作物品质,从而实现农业绿色可持续发展和循环经济,最终形成种养结合型生态循环农业模式的长效机制。该文概述了施羊粪改善土壤理化性质,提高土壤酶活性和微生物多样性,进而促进植物根系生长发育与农作物品质方面的研究进展,并展望了羊粪在未来农业发展中的应用趋势,旨在为农业绿色发展提供施肥依据。

水冬瓜根及茎的质量控制方法研究

目的建立水冬瓜根及茎药材的质量控制方法。方法观察水冬瓜根及茎药材的性状、显微特征;按2020年版《中国药典》(四部)通则方法对水冬瓜根及茎药材中的水分、总灰分、酸不溶性灰分和醇溶性浸出物进行测定;采用《中药色谱指纹图谱相似度评价系统(2012版)》建立11批水冬瓜根及茎药材的高效液相色谱(HPLC)指纹图谱,并进行共有峰的指认及相似度评价;采用HPLC法测定水冬瓜根及茎中松柏苷、紫丁香苷、绿原酸、(+)-syringaresinol-O-β-D-glucopyranoside、丁香脂素的含量。结果水冬瓜根及茎药材性状与显微鉴别特征明显。水分、总灰分、酸不溶性灰分和醇溶性浸出物的含量平均值分别为7.54%、2.18%、0.15%、7.81%。11批水冬瓜根及茎药材的指纹图谱有16个共有峰,相似度为0.856~0.960,共指认出松柏苷、紫丁香苷、绿原酸、(+)-syringaresinol-O-β-D-glucopyranoside、丁香脂素5个共有成分。上述5个成分的含量分别为0.0472~0.4016、0.8368~8.6979、1.2453~10.9500、0.1390~0.4378、0.0164~0.6353 mg/g。结论所建方法稳定、准确性好,可用于水冬瓜根及茎药材的质量控制。初步拟定水冬瓜根及茎药材中水分不得过11.0%,总灰分不得过4.0%,醇溶性浸出物不得少于5.0%,松柏苷、紫丁香苷、绿原酸、(+)-syringaresinol-O-β-D-glucopyranoside、丁香脂素含量分别不得少于0.04、0.83、1.24、0.13、0.01 mg/g。

油茶根腐病根际土壤、根系内真菌群落结构和多样性分析

为明确患根腐病的油茶在不同病情等级下根系和根际土壤内真菌群落组成、多样性、功能特征及与环境因子的关系,以德宏州梁河县的油茶为研究对象,利用高通量测序技术对5个病情等级的油茶根系及根际土壤内真菌的转录间隔区(internal transcribed spacer,ITS)序列进行测序。结果表明,染病油茶根系及根际土壤内的真菌群落多样性(Shannon指数)降低,根系中真菌总OTUs(operational taxonomic units)、特有OTUs和丰富度(Chao1指数)呈先增加后减少的趋势;根际土壤中染病油茶真菌群落的均匀度和丰富度上升。门水平上,子囊菌门(Ascomycota)和担子菌门(Basidiomycota)为根系及根际土壤中共同的优势菌门,球囊菌门(Glomeromycota)和被孢囊门(Mortierellomycota)在根系中丰度表现为逐级递减的趋势。属水平上,患病后油茶根系内树状孢属(Dendrosporium)、暗双胞属(Cordana)、Matsushimamyces、无柄盘菌属(Pezicula)、黑孢盘属(Melanconium)的丰度明显上升。油茶林下土壤真菌群落结构的主要影响因子为速效钾、有机质、pH、速效磷,真菌群落与环境因子联合分析结果表明,部分有益菌和磷含量呈正相关,部分病原菌和钾含量呈负相关。FUNGuild功能分析表明,油茶根系及根际土壤中真菌以腐生型为主,健康油茶中共生营养型真菌丰度最高,染病后逐渐降低;从Ⅱ级病害以后的油茶根系内植物病原功能群开始成为优势功能群。综上所述,油茶患病后真菌的多样性减少,根系内部分有益真菌丰度减少,植物病原菌和腐生菌增加,丛枝菌根真菌的定殖在调节油茶病健关系中发挥着重要的作用。针对德宏州梁河县的油茶基地,需要多施钾肥和磷肥,减少氮肥的施用,可提高部分有益菌的丰度,降低病原菌的丰度,从而减轻油茶根腐病的发生。

木醋液配施生物炭对盐碱土壤理化特性和甜菜产量及品质的影响

以甜菜品种KWS 1176为试验材料,在黑龙江省肇东市尚家镇五间村盐碱地(Na+含量为203.33 mg·kg^(-1),pH值8.92)进行小区试验。试验设4个处理,不施加木醋液(CK)、木醋液300 kg·hm^(-2)(BW1)、600 kg·hm^(-2)(BW2)和900 kg·hm^(-2)(BW3),各个处理均施用生物炭(玉米秸秆),用量为600 kg·hm^(-2)。研究表明,木醋液配施生物炭显著提高土壤比表面积(提升1.39%~4.86%)和含水率,降低土壤pH和电导率;显著提高当季土壤有机质和养分(碱解氮、有效磷)含量,播后58 d土壤有机质和养分提升效果显著,其中碱解氮含量、有效磷含量和有机质含量分别提升14.24%~26.87%、21.17%~32.09%和2.51%~41.19%。BW2处理土壤中Ca^(2+)、Mg^(2+)、SO_(4)^(2-)和Cl^(-)含量显著提高,可溶性Na^(+)和HCO_(3)^(-)含量显著降低;显著提高甜菜块根产量和品质,降低块根中钠盐含量、钾盐含量和α-氨基态氮含量,比CK处理块根产量提升5.32%~15.29%,块根含糖率提升0.31%~0.84%。综合分析,BW2对改善当季盐碱土壤理化特性及甜菜块根产量和品质效果最佳。

干湿交替下黄土区苜蓿根系抗拔力学性能

[目的]研究黄土区干湿交替过程对草本植物根系抗拔力学性能的影响,以期为草本植物根系固土护坡工程提供一定的理论支持和依据。[方法]选取紫花苜蓿为研究对象,采用重塑土根系拉拔试验,研究苜蓿根系抗拔力学性能及其与根径、根长、土壤容重、干湿交替作用等影响因素的关系。[结果](1)苜蓿根系抗拔力学性能指标与根径、根长和土壤容重存在幂函数或指数函数关系。(2)相比未干湿交替试样,干湿交替试样根系抗拔力学性能指标均显著减小。(3)砂壤土中苜蓿根系抗拔力学性能指标均优于壤土,且干湿交替在砂壤土中对苜蓿根系抗拔力学性能指标的影响小于在壤土中的影响。(4)根径、根长及容重和干湿交替的耦合作用对根系抗拔力学性能指标有显著影响。[结论]在干湿交替作用下,根径、根长和土壤容重对苜蓿根系抗拔力学性能有一定影响。

外源水杨酸对淹水胁迫下西瓜幼苗光合特性及抗氧化酶系统的影响

以‘雪龙1号’西瓜品种为材料,采用不同浓度(0.0、0.5、1.0、1.5、2.5、3.5 mmol/L)水杨酸(SA)溶液喷施幼苗叶片,测定淹水胁迫下西瓜幼苗的生长性状、根系构型、光合参数、叶绿素含量、SPⅡ光能转换效率和抗氧化酶活性等指标,结合主成分分析,研究水杨酸处理对淹水胁迫下西瓜幼苗生理特性的影响。结果表明:喷施SA溶液缓解了淹水胁迫对西瓜幼苗的不利影响,提高了淹水胁迫下西瓜幼苗的叶绿素含量、类胡萝卜素含量、实际光化学效率PSⅡ和超氧化物歧化酶、过氧化氢酶、过氧化物酶活性,降低了植株的丙二醛(MDA)含量,提高了植株耐涝性;与0.0mmol/L的SA处理相比,1.0mmol/LSA处理的西瓜幼苗的株高、茎粗、鲜质量、干质量分别显著提高18.80%、34.74%、23.57%、67.27%;总根长、根尖数分别显著提高116.41%、101.25%;叶绿素a、叶绿素a+叶绿素b、类胡萝卜素含量分别提升了66.55%、67.46%、73.81%;CAT活性显著提高20.92%,MDA含量显著下降53.32%;主成分分析结果表明,1.0、1.5、2.5、0.5、3.5、0.0 mmol/L SA处理的西瓜的耐涝性依次降低。

水稻根系和土壤性状与稻田甲烷排放关系的研究进展

甲烷(CH_(4))是大气中最主要的温室气体,对全球气候变暖具有重要影响。稻田是农业生态系统中CH_(4)的主要排放源,水稻根系与土壤是影响稻田CH_(4)排放的关键因素。因此,探究水稻根系和土壤性状与稻田CH_(4)排放的关系对于缓解温室效应具有重要的意义。本文综述了稻田CH_(4)产生和排放的机理及其与水稻根系和土壤性状间的内在关系,并展望了进一步探究水稻和土壤性状与稻田CH_(4)排放关系的研究方向,为实现水稻丰产与固碳减排协同提供参考。

黄土丘陵区典型草本根系特征对土壤抗剪特性的影响

[目的]探讨退耕还林(草)工程实施20年以来,退耕地植物根系特征对土壤抗剪特性的影响,旨在为新时期黄土高原植被恢复和水土保持效益评估提供参考。[方法]选取黄土高原丘陵沟壑区不同演替阶段6个典型草地和2个人工草地,采集土壤表层(0—5 cm)土样120个,测定土壤抗剪特性、土壤性质和根系特征指标。[结果](1)各样地土壤容重无显著的差异(p>0.05),毛管孔隙度、总孔隙度和土壤含水量存在显著差异(p<0.05),其中人工草地毛管孔隙度和总孔隙度相对较小,白羊草样地土壤含水量最低。(2)不同演替阶段须根系植物根长密度和表面积密度较大在不同演替阶段均大于直根系植物,须根系植物根体积密度除演替初期外均小于直根系植物,人工草地沙打旺上述根系特征参数均不同程度小于自然撂荒草地。(3)各样地平均根土复合体抗剪强度相较于素土增加了22.11%~46.22%,但自然撂荒草地平均抗剪强度差异不显著(p>0.05)。人工草地黏聚力整体低于自然撂荒草地,不同演替阶段内摩擦角均表现为须根系植物大于直根系植物(1.07,1.25,1.23倍)。(4)黏聚力随总孔隙度(R^(2)=0.82)或根体积密度(R^(2)=0.47)的增加呈线性增大,内摩擦角随土壤容重的增加呈线性减少(R^(2)=0.39)。[结论]在植被恢复过程中,土壤性状、根系特征及根系构型对土壤抗剪特性有一定影响。