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.

Production Performance of Root Systems of Four Forage Legume Species and Their Development Characteristics in Loess Plateau,China

Production performance of four forage legumes species of Medicago sativa,Onobrychis viciifolia,Lotus corniculatus and Galega officinalis were determined,including plant height,above-ground biomass per unit area,tillers per unit area,fertile tillers per unit area,shoot /leaf ratio and fresh /dry matter weight ratio,and the distribution characteristics of their root systems in 0- 100 cm soil layers with 10 cm interval were studied. Results showed that the average aboveground fresh biomass(4 a and 5 a) of four forage legumes species successively were L. corniculatus 】 M. sativa 】 O. viciifolia 】 G. officinalis. The average plant heights in two years successively were O. viciifolia 】 M. sativa 】 G. officinalis 】 L. corniculatus. Tillers per unit area of four forage legume species in two years successively were M. sativa 】 L. corniculatus 】 O. viciifolia 】 G. officinalis. Fertile tillers per unit area in two years were O. viciifolia 】 M. sativa 】 L. corniculatus 】 G. officinalis. Average shoot /leaf ratio in two years were G. officinalis 】 M. sativa 】 O. viciifolia 】 L. corniculatus. Average moisture contents of four forage legume species in two years successively were G. officinalis 】 L. corniculatus 】 M. sativa = O. viciifolia. The distribution characteristics of root systems of four forage legumes species in 0- 100 cm soil layers were as follows: the root weights of M. sativa in 0- 40 cm soil layers accounted for about 98. 3% of total root weight,that of O. viciifolia in 0- 30 cm soil layers was 85. 8%,that of L. corniculatus in 0- 10 cm soil layers was 80%,and that of G. officinalis in 0- 40 cm soil layers was 81. 4%. The results suggested that L. corniculatus was suited to plant in slighter degraded pasture to control water and soil erosion in early stage,G. officinalis with strong lateral roots was adapted to degraded grassland in the Loess Plateau where soil nutrient was poor,while O. viciifolia and M. sativa with potentially strong main root were fit for water and soil conservation in the losses plateau for long term.

Optimal root system strategies for desert phreatophytic seedlings in the search for groundwater

Desert phreatophytes are greatly dependent on groundwater, but how their root systems adapt to different groundwater depths is poorly understood. In the present study, shoot and root growths of Alhagi sparsifolia Shap. seedlings were studied across a gradient of groundwater depths. Leaves, stems and roots of different orders were measured after 120 days of different groundwater treatments. Results indicated that the depth of soil wetting front and the vertical distribution of soil water contents were highly controlled by groundwater depths. The shoot growth and biomass of A. sparsifolia decreased, but the root growth and rooting depth increased under deeper groundwater conditions. The higher ratios of root biomass, root/shoot and root length/leaf area under deeper groundwater conditions implied that seedlings of A. sparsifolia economized carbon cost on their shoot growths. The roots of A. sparsifolia distributed evenly around the soil wetting fronts under deeper groundwater conditions. Root diameters and root lengths of all orders were correlated with soil water availabilities both within and among treatments. Seedlings of A. sparsifolia produced finer first- and second-order roots but larger third- and fourth-order roots in dry soils. The results demonstrated that the root systems of desert phreatophytes can be optimized to acquire groundwater resources and maximize seedling growth by balancing the costs of carbon gain.

The influence of plant root system architectural properties upon the stability of loess hillslopes,Northeast Qinghai,China

To investigate the influence of root system architectural properties of three indigenous(coldadapted) shrubs on the hillslope stability of loess deposits in the Xining Basin,northeast part of Qinghai-Tibet Plateau(QTP),indoor direct shear tests have been conducted on the remolded rooted soil of three shrubs.Test results show that root system architectural indices(root area ratio(RAR),root length density(RLD) and root density(RD)) of the shrubs decline with depth and the relationship between RAR,RD and depth is exponential,while a power relationship describes the relationship between RLD and depth.The cohesion force of remolded rooted soil for the shrubs initially increases withdepth,but it then demonstrates a slightly decreasing trend,which can be described with a power relationship.Power relationships also describe relationships between cohesion force and RAR,RLD and RD for the shrubs.As the growth period increases from 10 to 17 months,the incremental increase in RAR is 48.32% ~ 210.25% for Caragana korshinskii Kom and 0.56% ~ 166.85% for Zygophyllum xanthoxylon(Bunge) Maxim.This proportional increase is notably larger than that for RLD and RD.The increment in RAR is marginally greater for C.korshinskii than it is for Z.xanthoxylon.Correspondingly,the cohesion force incremental rates of remolded rooted soil for C.korshinskii and Z.xanthoxylon are 12.41% ~ 25.22% and 3.45% ~ 17.33% respectively.Meanwhile,as root content increases,the contribution by roots to cohesion force increases markedly until a threshold condition is reached.

宁夏南部黄土丘陵区3种草本根土复合体抗冲性及其与影响因素的关系

[目的]明确宁夏南部黄土丘陵区3种草本根土复合体抗冲性差异及其与相关影响因素的关系,为研究区生态建设质量提升及植被优化配置提供理论依据。[方法]以研究区常见草本百里香、星毛委陵菜、长芒草根土复合体为研究对象,采用室内原状土水槽冲刷法,并利用LA-S根系扫描分析系统,研究不同草本0—15 cm土层根土复合体抗冲性能及其与根、土的关系。[结果](1) 3种草本0—15 cm土层根土复合体抗冲性大小为星毛委陵菜(53.7 L·h/g)>百里香(36.5 L·h/g)>长芒草(14.2 L·h/g),星毛委陵菜根土复合体抗冲性最强。(2) 3种草本根系根长密度、表面积密度、体积密度和比根长分别为4.25~10.56 cm/cm^(3),42.95~111.51 mm^(2)/cm^(3),5.04~17.94 mm^(3)/cm^(3),35.06~67.96 m/g,根长密度等参数百里香明显大于其他草本。(3)各草本根系分布土壤的有机碳含量百里香(1.437%)>星毛委陵菜(1.290%)>长芒草(0.430%)。根系土壤黏粒含量百里香是星毛委陵菜、长芒草的1.14倍、1.20倍。3种草本土壤团聚体参数MWD,GMD,R_(>0.25)分别为13.80~18.23 mm, 7.15~11.11 mm, 43.06%~70.05%,各指标星毛委陵菜最大。(4)根系、土壤均能直接或间接、单独或共同影响根土复合体抗冲性。百里香土壤黏粒、粉粒、砂粒及团聚体直接影响土体抗冲性,其大部分根系还通过影响土壤机械组成和有机碳含量间接影响抗冲性。星毛委陵菜土壤粉粒和大部分细根直接影响土体抗冲性,其0~0.5 mm根、土壤黏粒、砂粒还通过影响土壤团聚体等间接影响抗冲性。长芒草土壤砂粒、0~1.0 mm根直接影响土体抗冲性,其特定细根还通过影响土壤团聚体和有机碳含量间接影响抗冲性。[结论]3种草本根土复合体抗冲性大小有明显差异,根系、土壤均能影响其抗冲性能,在宁夏南部黄土丘陵区进行生态建设应考虑不同草本(植被)的抗冲性能,并在改善相关影响因素的基础上加以科学配置。

Mechanisms for the Movement of Fe，Mn，Cn and Zn to Plant Roots in Loessal So il and Lon Soil

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土壤含水量对探地雷达探测植物根系构型精度的影响

根系是评价植被生态服务功能的关键基础要素,但快速、精确、无损确定根系的测量技术和方法是目前生态系统评估中的瓶颈。探地雷达是一种高效无损的地球物理学技术,可以在无损状态下获取土壤中的根系信息。但是探地雷达检测和识别根系的精度受土壤含水量、根系含水量、根径大小、根系埋藏深度等诸多因素影响,导致其在野外根系探测中适用性受限,为了探究土壤含水量对探地雷达探测根系精度的影响,本研究采用野外预埋根系的控制实验,根据探地雷达波速、振幅和根点反射系数的变化,分析了不同土壤含水量条件下根点识别率及根点距离均方根误差。结果表明:(1)根系探测中,探地雷达波速和振幅是判断土壤含水量变化的重要参数;(2)随着土壤含水量的增大,探地雷达波速减小,雷达振幅趋于平缓;(3)不同土层深度上随着根系直径的增大,探地雷达波速增大,雷达振幅趋于激烈;(4)根点识别率与土壤含水量成负相关(P<0.05),土壤含水量为15%~25%时探地雷达对活根的识别效果最佳。本研究表明探地雷达可以作为植物根系生物量无损和快速测定、评估的方法,但在利用探地雷达测定土壤中根系时,应在土壤含水量相对较低的时间段进行。

接种AMF对西部煤矿区紫穗槐根系分布和水分利用效率的影响

西部干旱半干旱煤矿区井工开采导致了大面积采煤沉陷区的出现,矿区生态复垦难度较大,利用菌根微生物技术进行生态修复已经成为当前的研究热点。为探究接种丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)对紫穗槐根系分布特征和水分利用效率(Water Use Efficiency,WUE)的影响,研究通过室内土柱试验,设置了对照不种植紫穗槐幼苗(CK1)、种植紫穗槐幼苗(CK)、种植紫穗槐幼苗并接种AMF(+AM)3组试验处理,并对植物生长指标和土壤水分等进行了测定。结果表明:①接种AMF有效促进了紫穗槐的生长,其株高、SPAD(Soil and plant analyzer development)值、地上生物量和地下生物量相较CK处理分别提升38.5%、27.5%、11.1%、69.4%;②接菌改变了紫穗槐的根系分布,使总根系长度和根尖数分别增加329.0%和586.1%,平均根直径显著减小22.9%,2 mm以下细根根长比例提升370.1%。同时,接菌影响了土壤水分分布和紫穗槐的水分利用模式,使0~20 cm的土壤含水率较CK处理分别提高8.9%、7.8%,20~50 cm的含水率又分别降低16.8%、4.0%、11.6%;接菌增加了紫穗槐对表层5 cm以下土壤的水分利用比例,在5~30、30~50 cm分别提升15.4%、9.9%;③接菌使紫穗槐植株的WUE增加了27.5%,主成分分析结果表明,紫穗槐根系中的细根长(0.50~1.00 mm)和根尖数是干旱胁迫下接种AMF对土壤水分高效利用的关键根系特征。综上,接菌可对紫穗槐幼苗有明显的促生作用,通过对紫穗槐细根根系特征参数的显著改善,促进了对土壤水分的吸收及再分配能力,进而使紫穗槐植株表现出较高的WUE,该研究结果可为西部采煤沉陷区生物联合修复技术提供科学指导和技术支持。

不同密度可降解防草布对柑橘幼树生长及土壤性质的影响

本研究分析不同密度可降解防草布(低密度:52 g·m^(-2);中密度:72 g·m^(-2);高密度:82 g·m^(-2))对幼树生长及土壤性质的影响,旨在为柑橘幼树果园如何选择可降解防草布提供参考。结果表明,与对照相比,低密度和中密度可降解防草布对植株地上部分生长、根系在不同土层深度的分布比例均无显著性影响,但能造成根系总数量发生显著性减少。高密度可降解防草布能显著促进植株地上部分生长,不会引起根系总数量减少,但易造成根系分布在浅土层(0~<20 cm土层深度)。3种防草布对土壤容重无显著性影响,但能造成表层土壤含水量增加和深层土壤含水量减少,这可能是根系分布在浅土层的原因之一。因此,建议柑橘幼树果园选择高密度可降解防草布覆盖,但应考虑防草布覆盖前进行深层土壤改良,避免根系上浮。

沙棘根系固土力学特性对其平茬复壮的响应

为考察平茬措施对根系力学特性的影响,以内蒙古干旱半干旱地区水土保持先锋灌木沙棘(Hip-pophaerhamnoides)根系为研究对象,使用TY-8000拉力机,进行单根极限拉伸试验和根土界面拉拔摩阻试验,并分析平茬对沙棘根系固土力学特性的影响。试验结果显示,在测试根径为0~5mm时,平茬和未平茬条件下,沙棘单根极限抗拉力、抗阻拉力均与直径呈幂函数正相关;单根极限抗拉强度、根-土界面拉拔抗剪强度均与直径呈幂函数负相关。在代表根径级0.5~1.5mm,沙棘平茬较未平茬平均单根极限抗拉力值提高31%;平均单根极限抗拉强度提高37%;平均拉拔抗剪强度提高30%。研究结果表明,直径对沙棘根系抗拉强度和抗剪强度均有影响,且沙棘经平茬处理后,抗拉特性和抗剪特性均有所提高。

Tomato Root Response to Subsurface Drip Irrigation

Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the responses of a tomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse,to evaluate tomato growth as affected by subsurface drip irrigation,and to develop an integrated subsurface drip irrigation method for optimal tomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigation pipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but with yield and water use efficiency (WUE) significantly less (P ---- 0.05) than treatment 2; root activity and tomato yield were significantly higher (P = 0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots and shoots grew harmoniously with root activity,nutrient uptake,tomato yield and WUE significantly higher (P= 0.05) or as high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth with a drip-proof flume placed underneath was best for tomato production in greenhouses. In addition,the irrigation interval should be about 7-8 days and the irrigation rate should be set to 225 m3 ha-1 per event.

油菜机械直播同步分层施肥对根系构型和抗倒伏能力影响

为探明油菜精量联合直播同步分层施肥机械作业条件下,深浅层施肥比例对油菜根系生长、植株抗倒伏能力和产量等农艺性状的影响,该研究选用“华油杂62”油菜品种作为供试作物,在施肥量600 kg/hm^(2)条件下,以10 cm定位侧深施肥CK1和机械旋耕浅层混施CK2作为对照,设置机械旋耕浅层混施-定位侧深施肥量分层比例为1∶3(FL)、1∶1(FM)和3∶1(FH)3个施肥处理,于2020年和2021年在长江中游冬油菜区开展田间试验,研究不同分层施肥处理对油菜根系分布、耕层土壤坚实度变化、倒伏指数和产量的影响。结果表明,分层深施处理能显著(P<0.05)改善油菜根系构型并促进根系下移,平均根表面积、根体积、根干质量和主根长分别是CK1处理的1.58、1.47、1.29和1.16倍,是CK2处理的3.63、2.79、1.46和1.28倍,且土壤坚实度相较于CK1和CK2处理平均分别降低4.91%和15.25%。不同分层施肥处理的油菜主根长、根表面积、根体积和根干质量在处理间从大到小依次均为:FM、FH、FL;FH处理植株的根茎粗、倒伏角度、抗折力分别是FM处理的1.11、1.25和1.31倍,倒伏指数相较于FM处理平均降低了26.90%,但植株田间倒伏角度比FM处理增加了25.14%。分层深施肥处理的产量、单株分枝数、角果数和千粒质量均显著(P<0.05)大于定位深施和机械混施处理,其中FM处理平均产量与FL、FH、CK1和CK2相比,分别提高9.85%、16.35%、26.88%和37.75%。综合考虑不同施肥处理下冬油菜根系分布、土壤坚实度、倒伏指数和籽粒产量,分层深施肥处理中FM处理为田间机械化直播冬油菜实现高产且抗倒伏的较优施肥方式,研究为提升油菜机械直播农机农艺融合和肥料运筹策略提供了理论依据和技术支撑。

黄河源区六种草本植物根系抗拔力特征及其影响因素研究

为探讨黄河源区高寒草地植物根系抗拔力特性,本研究选取青海河南县高寒草地6种优势草本为研究对象,通过原位拉拔、单根拉伸、根-土复合体直接剪切等试验,分析6种植物根系抗拔力特性,探讨植物根径、根数、根长和土体密度、含水率、紧实度、含根量及单根抗拉强度、根-土复合体黏聚力等9种因素对植物根系抗拔力的综合影响。结果表明:6种草本根系抗拔力以矮嵩草(Kobresia humilis K.)最大(46.50 N),高山嵩草(Kobresia pygmaea C.B.Clarke.)次之(37.50 N),冷地早熟禾(Poa crymophila Keng.)最小(16.45 N);根系抗拔力与根径、根数、根长间呈显著正相关(P<0.05),相关系数(R)为0.881,0.727,0.969,与土体密度、紧实度、含根量、根-土复合体黏聚力间呈正相关,与含水率呈负相关。研究结果对探讨黄河源区高寒草地退化力学机理具有理论指导作用,为有效防治区内草地退化、水土流失等地表浅层灾害发生提供理论依据和实际指导。

黄河源区不同禁牧年限对垂穗披碱草单根及其根-土复合体力学强度特征的影响

为研究黄河源区不同禁牧年限高寒草地植物根系力学特性及根系增强土体抗剪强度贡献特征,本研究以黄河源区河南县地区未禁牧、1 a禁牧、4 a禁牧、10 a禁牧4种工况下的高寒草地植物垂穗披碱草为研究对象,在野外调查、取样及室内单根拉伸试验和根-土复合体直剪试验的基础上,探讨了垂穗披碱草在不同禁牧年限下,单根抗拉力和根-土复合体抗剪强度指标变化特征及其影响因素。结果表明:1~4 a短期禁牧增加了垂穗披碱草生长量指标,而10 a长期禁牧其生长量指标则呈降低的变化特征。随着禁牧年限增加,垂穗披碱草单根抗拉力呈先增大后降低的变化规律,1和4 a禁牧单根抗拉力较未禁牧增幅分别为15.9%、14.8%;垂穗披碱草单根抗拉强度、根-土复合体黏聚力均呈降低趋势,其中10 a禁牧垂穗披碱草单根抗拉强度、根-土复合体黏聚力相对于未禁牧降低幅度最大,分别为57.3%、63.5%。进一步研究表明,根-土复合体黏聚力c值与根径、土体密度之间呈显著正相关关系,与含水率之间则呈显著负相关关系,且黏聚力c值随含根量的增加呈先增大后减小的变化规律。研究结果可为高寒地区开展草地退化、水土流失等灾害的有效防治提供理论支撑和实际指导。

不同植被类型根系对土壤水分分布的影响

为探究不同植被类型下的根系对土壤水分分布的影响,以江西省北部武宁县的典型针阔混交林、毛竹林和休耕地为对象,采用染色示踪实验,并观测和采集土壤和根系样品,分别测定0~20,20~40和40~60 cm土层的土壤理化性质、植物根系特征、土壤蓄水性能和土壤团聚体稳定性等指标,分析不同植被类型其对土壤水分分布的多重影响和影响机制。结果表明:1)针阔混交林和毛竹林均在0~60 cm土层出现大面积的染色情况,而休耕地则仅在0~20 cm土层出现,且根系越多的土层,染色面积往往越突出;2)随着土层深度的增加,土壤含水量、最大持水量、饱和含水量,有机质含量,平均质量直径和几何平均直径均显著降低(P<0.05);3)针阔混交林和毛竹林的根系数量分别为休耕地的16.96和30.95倍,其深层(40~60 cm)的蓄水能力(最大持水量)分别高出休耕地3%和10%,土壤团聚体稳定性(平均质量直径)分别高出13%和23%;4)根系特征指标、土壤蓄水能力指标和土壤团聚体稳定性指标均与染色面积比显著正相关(P<0.05)。综上,3种类型样地中,土壤中丰富的根系对土壤蓄水能力和土壤团聚体稳定性均显示出明显的促进作用,进一步促进土壤中的水分分布。因此针阔混交林和毛竹林的水分分布程度均强于休耕地。为有效提升区域水土保持功能和生态风险抗性,需加强森林资源的管理和保护,提高林地植被的多样性以提高地下根系的分布密度和深度。

不同植物对黄土边坡产流产沙与抗剪强度的影响

[目的]探讨不同草本植物对黄土边坡产流产沙与抗剪强度特征的影响,为进一步开展高寒干旱和半干旱地区,有效防治因降雨诱发水土流失、浅层滑坡等地质灾害,提供理论依据和实际指导。[方法]在西宁盆地长岭沟流域自建试验区,选取垂穗披碱草(Elymus nutans)、老芒麦(Elymus sibiricus)、细茎冰草(Agropyron trachycaulum)3种优势草本植物为试验供试种,开展原位人工模拟降雨试验与室内直剪试验,分析了模拟降雨条件下6种不同类型植物边坡坡面产流产沙及根—土复合体抗剪强度特征。[结果]在模拟降雨条件下,草本植物能显著抑制坡面产流产沙,阶梯形边坡相对直形边坡能显著降低坡面产流产沙,且随着草本生长期增加坡面产流产沙显著降低,生长期为2 a的种植垂穂披碱草阶梯形边坡坡面累积产沙量较垂穂披碱草直形边坡降幅为79.68%,生长期为1 a的种植垂穂披碱草阶梯形边坡平均产沙率较阶梯形未种植裸坡降低幅度最大为86.27%,表明种植垂穂披碱草阶梯形边坡有效抑制坡面的产流能力相对显著;进一步研究表明,降雨使边坡土体平均含水率增大,导致边坡浅层土体黏聚力降低;与直形边坡相比较,模拟降雨后阶梯形边坡黏聚力c值降低幅度较小,其中种植垂穂披碱草阶梯形边坡较降雨前降低幅度为19.25%,表明垂穂披碱草阶梯形边坡其增强边坡土体强度效果相对最显著。[结论]垂穗披碱草阶梯形边坡表现出相对更显著的抑制边坡水土流失和提高边坡浅层土体抗剪强度,起到增强边坡土体稳定性的作用。

重庆缙云山植物幼苗根系及土壤对酸雨的响应机制

为研究酸雨对植物根系和土壤碳(C)、氮(N)、磷(P)含量、生态化学计量比特征及根系形态影响,以重庆乡土树种马尾松(Pinus massoniana)、杉木(Cunninghamia lanceolata)、香樟(Cinnamomum camphora)、毛竹(Phyllostachys edulis)为研究对象,于2021年5月进行酸雨模拟试验,设置4个不同处理水平,即CK(pH7.0蒸馏水)、pH4.5、pH3.5和pH2.5;模拟酸雨环境4个月后对植物根系形态及土壤和根系C、N、P含量进行测定。结果表明:1)在pH3.5条件下,杉木和香樟根系全氮含量受到显著抑制(P<0.05),与对照组相比,分别降低18.86%、35.66%,在pH4.5条件下马尾松土壤有机碳储量升高而毛竹土壤全氮产生流失;2)酸雨对各植物-土壤C∶N∶P影响不同,杉木、香樟根系C∶N在pH3.5条件下显著上升至50.26、61.33;在酸雨处理下,根系氮和磷变化趋势一致,马尾松、杉木、毛竹受到氮元素限制;3)不同植物根系在酸雨影响下表现不同,酸雨促进马尾松和杉木根系生长,抑制香樟和毛竹根系生长;4)根系形态与根系C∶N和根系全碳含量显著正相关,而与根系N∶P显著负相关。短期酸雨尚未破坏各植物-土壤整体平衡,杉木土壤缓冲能力强于马尾松、香樟、毛竹土壤,且根系对酸雨响应更加积极。

间套作模式在棉田上的研究进展

为进一步提高棉田经济效益并保证棉花种植面积的稳定性,因地制宜,改变植棉栽培技术,选择合适的种植结构和作物布局是促进棉花生产高质量发展的重要措施。其中,间套作模式在棉田中的理论研究与应用得到广泛关注。概括了棉田中主要的间套作模式,并总结了各种间套作模式的增产优势,阐述了间套作模式对棉花生长发育、光合特性、养分吸收利用、根系形态特征、产量、品质及土壤理化性质的影响。同时,根据目前间套作模式在棉花实际生产上存在的问题对其应用前景做出展望,以期为今后深入研究间套作模式在棉花生产上的应用提供参考。

践踏对2种草坪草土壤物理性质与根系的影响

以长三角地区常用的结缕草(Zoysia japonica‘兰引3号’)和杂交狗牙根(Cynodon dactylon×Cynodon transvadlensis‘Tifdwarf’)为试验材料,基于公园不同客流量下的草坪土壤紧实度设置不同践踏强度,探索不同草坪草应对大客流的耐践踏特性及制定恢复措施的优先衡量指标。随践踏强度增加,2种草坪的表层土壤容重增加,孔隙度、通气度和持水量下降。其次,践踏显著降低了狗牙根的根生物量,重度践踏显著降低了其地上生物量,而结缕草表现出更强的应对各强度践踏胁迫时的能力,其地上生物量和根系构型特征分别在轻度和中度践踏时达到最大值。最后,草坪草的根长与地上生物量、根生物量、根体积、根投影面积均呈显著正相关,根体积与其余3个根系构型特征均呈显著正相关;进一步通过主成分分析发现,根体积、根投影面积和根长的重要值排在前3位,在草坪耐践踏评估及制定恢复措施时需加以考虑。

指数分布型根系根-土复合体强度特性研究

指数分布型是排土场护坡植物根系中十分常见的根型,为进一步揭示根-土复合体固土护坡的内在机理,针对现有数值模拟方法不易还原自然条件下根系真实形态的问题,结合土工试验,优化数值模拟方法,研究了细观尺度下指数分布型根系根-土复合体的力学强度特性,结果表明:根-土复合体试样表现出与素土不同的颗粒位移特征,根系的存在能够显著提高土体的整体性,根的张拉作用限制了土体的侧向变形;构建的根-土复合体离散元模型可以较好地反映含根系土壤的力学效应,根系内部应力主要集中于剪切平面附近的根系部,各垂直荷载下未发现根系整体贯通断裂,断裂整体上呈现出在剪切平面集中、土体内零星分布的特点;素土试样的剪应力-剪切位移曲线呈现出带有波峰的应变软化趋势,而根-土复合体试样呈现出无波峰的应变硬化趋势;草本植物根系主要增大了根-土复合体的黏聚力,对内摩擦角的影响不明显。研究成果对于深入了解根土相互作用加固土壤的机理和推进根-土复合体的数值模拟研究具有重要的参考意义。