Effective root depth and water uptake ability of winter wheat by using water stable isotopes in the Loess Plateau of China

A field experiment using PVC growth tubes was conducted in the Loess Plateau of China to determine the effective root depth(ERD)of winter wheat and its relationship with root distributions and soil water conditions.The water stable isotopes technique was used to estimate the water uptake contributions of different root depths during the growth stages.On the basis of IsoSource and the Romero-Saltos model,the ERD was 0-40 cm in the majority of the growth stage.However,in the heading and filling stages,the ERD could reach 60%-75%of the maximum root depth.Furthermore,the contributions to water uptake of different root depths were correlated with variations in soil water and root length density(r=0.395 and 0.368,respectively;p<0.05).However,by path analysis,the low decisive coefficient indicated that root distribution and soil water content did not always follow the same trend as water uptake.The conclusions of this study can help with understanding winter wheat water uptake mechanisms in arid and semi-arid regions and increasing water use efficiency.

iRoot SP配合单尖法根管充填治疗牙体牙髓病的效果及对牙周状态和龈沟液炎性因子水平的影响

目的 探讨iRoot SP配合单尖法根管充填治疗牙体牙髓病的效果及对牙周状态和龈沟液炎性因子水平的影响。方法 选取2020年1月—2022年1月收治的牙体牙髓病82例,按治疗方法分为观察组和对照组各41例,观察组应用iRoot SP配合单尖法治疗,对照组应用iRoot SP配合冷测压法治疗。比较2组临床疗效、充填情况、牙周状态、龈沟液炎性因子水平及疼痛情况。结果 治疗后,观察组临床总有效率和恰填率高于对照组(P<0.05)。观察组治疗后牙周探诊深度、探诊出血指数、牙齿松动度、菌斑指数、临床附着水平及超敏C反应蛋白、肿瘤坏死因子-α、白细胞介素-1β均低于对照组(P<0.05,P<0.01)。治疗后,观察组疼痛总发生率低于对照组(P<0.05)。结论 iRoot SP配合单尖法根管充填能够提高牙体牙髓病的临床疗效,改善患者充填情况以及牙周状态,降低龈沟液炎性因子水平及减轻患者疼痛。

Variability of water supply affected shoot biomass and root depth distribution of four temperate grassland species in monocultures and mixtures

极端降雨事件对生态系统功能影响的研究主要集中在干旱或洪水事件,通常包括全年或某个季度的平均或总降雨量的变化。然而,在不改变平均量或总量的情况下,增加降雨变异性的影响还很少被研究。本研究调查了增加水分供应变异性对单一栽培和混合栽培下4种草原植物的地上和根系生物量以及根系生物量分布的影响。将多年生黑麦草(Lolium perenne L.,浅根),菊苣(Cichorium intybus L.,深根),白车轴草(Trifolium repens L.,浅根)和红车轴草(Trifolium pratense L.,深根)种植在中型实验生态系统中。单一栽培条件下种植4株同种植物,混合栽培条件下每种植物各1株。水分供应变异性处理设置低中高3种水平:与低变异水分供应处理相比,另设置一个中度变异处理(±40%)和高度变异处理(±80%),测定了地上和根的生物量,拟合了根系垂直分布模型。研究结果表明,与低变异处理相比,白车轴草,红车轴草和4种植物混种群落的茎生物量在高变异处理下显著减少。在所有处理中,4种植物混种群落产生的茎和根生物量比单一栽培(超产)中物种表现所预测的要多。在水分变异增加的情况下,菊苣在单一栽培下根系分配了更多的生物量到更深的土层,而白车轴草在单一栽培下根系总生物量显著降低。这些结果表明,水分供应变异的增加会对单一栽培和混合栽培草地的地上和根的生物量产生负面影响。在野外尺度上,水分变异对多物种草地系统功能的影响需要进一步研究。

Responses of root growth of Alhagi sparsifolia Shap. (Fabaceae) to different simulated groundwater depths in the southern fringe of the Taklimakan Desert, China

Alhagi sparsifolia Shap. （Fabaceae） is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the dis- tribution of one-year-old A. sparsifolia seedlings to different groundwater depths in controlled plots. The eco- logical adaptability of the root systems of A. sparsifolia seedlings was examined using the artificial digging method. Results showed that： （1） A. sparsifolia seedlings adapted to an increase in groundwater depth mainly through increasing the penetration depth and growth rate of vertical roots. The vertical roots grew rapidly when soil moisture content reached 3%-9%, but slowly when soil moisture content was 13%-20%. The vertical roots stopped growing when soil moisture content reached 30% （the critical soil moisture point）. （2） The morphological plasticity of roots is an important strategy used by A. sparsifolia seedlings to obtain water and adapt to dry soil conditions. When the groundwater table was shallow, horizontal roots quickly expanded and tillering increased in order to compete for light resources, whereas when the groundwater table was deeper, vertical roots developed quickly to exploit space in the deeper soil layers. （3） The decrease in groundwater depth was probably respon- sible for the root distribution in the shallow soil layers. Root biomass and surface area both decreased with soil depth. One strategy of A. sparsifolia seedlings in dealing with the increase in groundwater depth is to increase root biomass in the deep soil layers. The relationship between the root growth/distribution of A. sparsifolia and the depth of groundwater table can be used as guidance for harvesting A. sparsifolia biomass and managing water resources for forage grasses. It is also of ecological significance as it reveals how desert plants adapt to arid environments.

抗菌光动力疗法辅助龈下刮治治疗慢性牙周炎临床效果观察

目的探讨抗菌光动力疗法(antibacterial photodynamic therapy,aPDT)辅助龈下刮治和根面平整(scaling and root planing,SRP)治疗慢性牙周炎的临床效果。方法本研究已通过单位伦理委员会审查通过,并获得患者知情同意。研究采用随机、对照分口设计,符合纳入标准的16例慢性牙周炎患者随机分为试验侧与对照侧。对照侧接受常规SRP,试验侧SRP基础上联合aPDT治疗(SRP+aPDT)。记录治疗前(基线)、治疗后1个月、3个月和6个月时牙周探诊深度(probing depth,PD)、菌斑指数(plaque index,PLI)、出血指数(bleed⁃ing index,BI)和探诊出血(bleeding on probing,BOP)阳性位点占比(BOP%)。结果13例患者完成了全部随访。对照侧356颗受试牙,2136个位点;试验侧360颗受试牙,2160个位点。治疗前,两侧基线水平各指标差异无统计学意义。在治疗后1个月、3个月和6个月时,试验侧和对照侧的牙周临床指标PD、PLI、BI、BOP%相较于治疗前均有明显改善(P<0.05)。在各时间点,与常规SRP相比,SRP+aPDT联合治疗侧PD、PLI和BI均有改善。SRP+aPDT联合治疗侧在治疗后3个月时BOP%和PLI的改善明显优于常规SRP侧(P<0.05)。结论aPDT辅助治疗慢性牙周炎可以在早期更好地改善牙龈出血,控制牙周炎症。

耕翻深度对阴山北麓地区马铃薯根系生长及土壤酶活性的影响

为探究耕翻深度对阴山北麓地区马铃薯根系生长及土壤酶活性的影响,分析了4个耕翻深度20 cm(D_(20),CK)、30 cm(D_(30))、40 cm(D_(40))、50 cm(D_(50))对马铃薯根干物质积累量、根系活力以及土壤过氧化氢酶、碱性磷酸酶、脲酶、蔗糖酶活性的影响。结果表明:较D_(20)和D_(30)处理,深翻D_(40)和D_(50)处理可显著提高根系活力,促进淀粉积累期马铃薯根系干物质积累,分别提高了75.2%~292.1%和23.4%~30.2%。通过土壤酶活性分析,深翻(D_(30)、D_(40)、D_(50)处理)对马铃薯田中过氧化氢酶、蔗糖酶活性影响不明显,但对碱性磷酸酶与脲酶活性影响较大。深翻可提高马铃薯全生育期0~20 cm土层及苗期20~60 cm土层中碱性磷酸酶活性,其中在块茎膨大期至淀粉积累期0~20 cm土层与苗期40~60 cm土层中D_(40)和D_(50)处理影响显著。深翻D_(30)、D_(40)、D_(50)处理分别显著提高了0~20 cm土层中整个生育期、块茎膨大期和淀粉积累期、淀粉积累期的脲酶活性;同时还提高了20~60 cm土层中脲酶活性,其中D_(40)和D_(50)处理显著提高了33.8%~80.0%。综上所述,深翻30 cm仍旧是马铃薯根系生长的胁迫深度,深翻40 cm对促进马铃薯根系生长、提高马铃薯田土壤碱性磷酸酶与脲酶活性效果最佳。

漂浮植被作用下水流纵向流速的垂向分布及离散特性研究

为探究漂浮植被影响下明渠水流流速及纵向离散系数的沿程变化特性,采用Fluent软件中的k-ε模型进行三维数值模拟并与水槽试验结果进行对比分析,在模型验证合理的基础上,对漂浮植被不同根系下探深度及覆盖率下水流纵向时均流速的垂向分布特性进行研究,并基于改进的分区模型分析了含漂浮植被明渠的纵向离散系数。结果表明:漂浮植被水流垂向上可分为含植被水流层、无植被水流层与近河床层。纵向流速最大值出现在无植被水流层,其大小与植被下探深度及覆盖率呈正相关。含植被水流层的纵向流速随植被根系下探深度和覆盖率的增加而减小,无植被水流层及近河床层的纵向流速随着下探深度和覆盖率的增大而增大,且植被覆盖率及下探深度越大含植被水流层与无植被水流层的流速差异越大。纵向离散系数沿程表现出先增大后减小的趋势,在植被区中下游离散最为剧烈,且与植被下探深度和覆盖率呈正相关。

Root-ZX根管长度测定仪临床应用体会

目的:探讨Root-ZX根管长度测量仪测量根管长度的准确性。方法:将131例(242个)需进行治疗的根管随机分为实验组和对照组,实验组43例(83个根管)采用Root-ZX根管长度测定仪测定根管工作长度;对照组88例(159个根管)采用X线片+诊断丝方法测量根管工作长度。两组均采用冠向下技术进行根管预备,插30#牙胶尖拍片评价2种方法测量根管工作长度的准确性并进行比较。结果:实验组83个根管中68个根管测量准确,15个不准确;对照组159个根管中94个测量准确,65个不准确。两组差异有统计学意义(χ2=12.819,P<0.01)。结论:Root-ZX根管长度测定仪测定根管工作长度比X线片+诊断丝测量方法更加准确。

不同潜水埋深对单叶蔷薇实生苗根系生长与构型的影响

目的:为了解单叶蔷薇干旱适应策略并为原生境植被修复提供科学依据。方法:以一年生单叶蔷薇实生苗为研究对象,设置30 cm(D30)、40 cm(D40)、50 cm(D50)、60 cm(D60)和70 cm(D70)5组潜水埋深梯度,利用根系扫描等方法分析其对蔷薇实生苗根系生长和构型的影响。结果:潜水埋深对内部连接总数(a)、外部连接总数(v_(0))、连接总数之和(Pe)、平均拓扑长度(b)和修正拓扑参数q_(a)、q_(b)有显著影响(P<0.05),对拓扑参数Ti无显著影响(P>0.05),q_(a)(0.33~0.73)、q_(b)(0.23~0.88)变化范围较大。整个试验过程根系始终维持50°~60°的低分支角度,但当地下水极端匮乏时(如D70组和对照组CK),根系分支角度有增大趋势。随着干旱胁迫加强,单叶蔷薇实生苗根系的生物量增长速度大于地上生物量增长速度;在D60组、D70组和CK组,根系积累相同生物量,v_(0)的增加速度大于a的增加速度;各组根系分支数增长速度始终小于根系连接数,随干旱程度加深差异呈缩小趋势,以上说明适度的干旱可促进根系分支。结论:单叶蔷薇实生苗根系构型及时响应环境水分变化,适应性极强。

根-土复合体岸坡渗流及稳定数值模拟

植物护岸中根系力学效应可显著提高岸坡浅层稳定性,但对降雨和水位变化等条件下,根系水力效应与力学效应之间相对关系变化对岸坡浅层稳定性影响的研究较少。采用数值分析方法模拟了岸坡根-土复合体从非饱和到饱和(降雨工况和水位上升工况)、从饱和到非饱和(水位下降工况)过程中根-土复合体水力效应对岸坡渗流场的影响,进一步分析了不同水力特性条件下根-土复合体对岸坡浅层稳定性的影响。模拟计算结果表明:(1)在设定的3种降雨强度下,根-土复合体的优先流入渗作用与降雨强度和降雨时间均呈正相关,而排水作用与降雨强度和降雨时间均呈负相关。在长历时的小降雨或短历时的强降雨情况下,由于降雨影响深度增大,根-土复合体水力效应带来的消极影响占主导地位。(2)在水位下降工况下,根-土复合体排水作用有滞后性,力学效应仍占主导地位;在水位上升工况下,根-土复合体增渗作用随水位上升速率增加而增强,根-土复合体的力学效应逐渐被水力效应所掩盖。研究结果对植物护岸工程应用具有借鉴意义,即使采用植物生态护岸,也应加强坡面排水和坡体排水措施。

不同水分调控对沿黄灌区向日葵水分利用影响研究

为探究达拉特旗黄河南岸灌区向日葵根系吸水来源及其利用策略,通过测定达拉特旗黄河南岸灌区向日葵木质部水及其各种潜在水源(降水、土壤水和地下水)的氢氧同位素组成(δD和δ18O),利用直接对比法和MixSIAR模型研究对比不同灌溉制度下向日葵不同生育期水分来源及各水源利用差异。结果表明,向日葵在苗期、拔节期、灌浆期和成熟期的吸水深度分别在0~30、0~50、0~70和30~90 cm土层。不同灌溉量下,向日葵的主要吸水层具有一定的差异。0~10、10~30、30~50、50~70、70~90 cm深度土壤水和地下水对向日葵平均贡献比例分别为22.17%、17.99%、18.74%、14.68%、15.97%和10.45%。通过相关性分析,50 cm以下土层水分贡献对产量提高有利,0~10 cm土壤水、30~50 cm土壤水和地下水利用对灌溉水利用效率具有正相关关系。设置灌溉定额为187.5 mm时能显著提高产量,灌溉定额为100 mm时,能显著提升灌溉水利用效率。

基于同位素的神东矿区植物吸水深度及生态水位研究

为了研究神东矿区煤炭开采造成的地下水位下降是否会对地表植被的生存产生威胁,以神东矿区分布最广泛的植物沙蒿为研究对象,采用水稳定同位素示踪技术研究神东矿区成年沙蒿的根系吸水深度,通过MixSIAR同位素混合模型分析成年沙蒿的土壤水分吸收策略。结果显示,研究区成年沙蒿的吸水的极限深度为2.5~3 m,沙蒿会较均匀的吸收不同深度的土壤水分,但其水分利用策略也会受到土壤含水率高低的影响。该研究揭示了研究区成年沙蒿的根系吸水深度和水分利用策略,从植物角度说明了该区域生态水位的下限是2.5~3 m。

Distribution and Quantity of Root Systems of Field-Grown Erianthus and Napier Grass

Cellulosic bioethanol produced from non-edible plants reduces potential food-fuel competition and, as such, is receiving increasing attention. In the raw material production of cellulosic bioethanol, the aboveground biomass of plants is entirely harvested;consequently, the plant roots represent the major source of organic matter incorporated into the soil. We selected Erianthus and Napier grass as the raw materials for cultivation in Asia. However, information about whether these 2 species provide sufficient root volume to sustain soil fertility is limited. Therefore, we examined the spatial distribution of the roots of these 2 plants, and quantified root mass and length. Erianthus and Napier grass were either grown in fields or greenhouses in Tokyo (Japan) and Lampung (Indonesia), and then their roots were exposed from adjacent soil profiles. Both species developed large, deep roots, penetrating 2.0-2.6 m deep into the soil. Root depth indexes showed that the roots of both species penetrated much deeper into the soil compared to monocot crop species, being more comparable to dicot species. Erianthus developed a root mass and length of 384-850 g·m-2 and 28.8-35.8 km·m-2, while the values for Napier grass were 183-448 g·m-2 and 15.6-43.6 km·m-2, respectively. These values exceeded the maximum values previously recorded for common crop species. Our study confirmed that Erianthus and Napier grass develop deep root systems, with substantially large biomass;hence, we suggest that both plants supply root biomass in large quantities, representing possible major sources of soil organic matter.

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.

Three-source partitioning of soil respiration by ^(13)C natural abundance and its variation with soil depth in a plantation

Partitioning soil respiration into three components is vital to identify CO_2 sink or source and can help us better understand soil carbon dynamics. However, knowledge about the influences of soil depth and the priming effect on soil respiration components under field has been limited. Three components of soil respiration（root respiration, rhizomicrobial respiration and basal respiration） in a plantation in the hilly area of the North China were separated by the 13 C natural abundance method. The results showed that the average proportions of rhizomicrobial respiration, root respiration and basal respiration at the 25-65 cm depths were about 14, 23 and 63 %, respectively. Three components of soil respiration varied with soil depth, and root respiration was the main component of soil respiration in deeper soil. The priming effect was obvious for the deep soil respiration, especially at the 40-50 cm depth. Thus, depth and priming effect should be taken into account to increase the accuracy of estimations of soil carbon flux.

A simple approach for the estimation of CO_2 penetration depth into a caprock layer

Caprock is a water-saturated formation with a sufficient entry capillary pressure to prevent the upward migration of a buoyant fluid. When the entry capillary pressure of caprock is smaller than the pressure exerted by the buoyant CO2plume, CO2gradually penetrates into the caprock. The CO2penetration depth into a caprock layer can be used to measure the caprock sealing efficiency and becomes the key issue to the assessment of caprock sealing efficiency. On the other hand, our numerical simulations on a caprock layer have revealed that a square root law for time and pore pressure exists for the CO2penetration into the caprock layer. Based on this finding, this study proposes a simple approach to estimate the CO2penetration depth into a caprock layer. This simple approach is initially developed to consider the speed of CO2invading front. It explicitly expresses the penetration depth with pressuring time, pressure difference and pressure magnitude. This simple approach is then used to fit three sets of experimental data and good fittings are observed regardless of pressures, strengths of porous media, and pore fluids(water,hydrochloric acid, and carbonic acid). Finally, theoretical analyses are conducted to explore those factors affecting CO2penetration depth. The effects of capillary pressure, gas sorption induced swelling, and fluid property are then included in this simple approach. These results show that this simple approach can predict the penetration depth into a caprock layer with sufficient accuracy, even if complicated interactions in penetration process are not explicitly expressed in this simple formula.

The Offset-Domain Prestack Depth Migration with Optimal Separable Approximation

The offset-domain prestack depth migration with optimal separable approximation, based on the double square root equation, is used to image complex media with large and rapid velocity variations. The method downward continues the source and the receiver wavefields simultaneously. The mixed domain algorithm with forward Fourier and inverse Fourier transform is used to construct the double square root equation wavefield extrapolation operator. This operator separates variables in the wave number domain and variables in the space domain. The phase operation is implemented in the wave number domain, whereas the time delay for lateral velocity variation is corrected in the space domain. The migration algorithm is efficient since the seismic data are not computed shot by shot. The data set test of the Marmousi model indicates that the offset-domain migration provides a satisfied seismic migration section on which complex geologic structures are imaged in media with large and rapid lateral velocity variations.

磷肥施用深度对谷子根系分布、氮素吸收利用和产量的影响

采用大田试验,设置5 cm(P5)、10 cm(P10)、15 cm(P15)和20 cm(P20)4个磷肥施用深度,以不施磷肥为对照(CK),研究磷肥施用深度对谷子根系分布、干物质积累和转运、氮素吸收利用、产量的影响,以期为谷子生产上磷肥的高效利用提供理论基础。结果表明,适当的磷肥施用深度能促进谷子根系生长,提高根长、根表面积和根干质量,整体表现为P15>P10>P5>P20>CK;随着磷肥施用深度的增加,深层土壤中谷子的根长、根表面积和根干质量增加,在20~40 cm土层表现为P20>P15>P10>P5>CK。适当的磷肥深施可以促进谷子干物质积累和转运,相较于P5处理,P10、P15和P20处理成熟期干物质积累量分别提高4.60%、10.29%和0.92%,干物质转移率分别提高6.49%、10.06%和-20.13%。磷肥深施提高了根系对深层土壤中氮素的吸收和利用,深层土壤尤其是20~40 cm土层中的有效氮含量较P5处理显著降低,P10、P15、P20处理成熟期谷子总氮积累量分别较P5处理提高3.91%、17.85%、5.31%,氮素吸收效率分别提高5.88%、19.12%、7.35%,氮肥偏生产力分别提高18.95%、32.88%、-1.26%。适当的磷肥深施可以提高穗粒质量、产量和收获指数,均表现为P15>P10>P5>P20>CK,P10、P15处理产量分别较P5处理提高18.98%、32.86%,P20处理较P5处理减产1.27%。综上,15 cm为最优磷肥施用深度,可促进谷子根系生长及下扎,提高根系对土壤中氮素的吸收和利用,促进干物质积累及转运,相较于磷肥5 cm浅施增产32.86%。

露天煤矿台阶爆破合理超深试验研究

针对吉郎德煤矿露天深孔台阶爆破根底率高等问题,首先采用常用的钻孔超深计算方法得到了钻孔超深的合理范围,并通过现场调查发现目前造成台阶根底率偏高的主要原因是炮孔超深过大导致岩石超挖严重,由此提出将钻孔超深由目前的1 m减小为0.8 m。而后在1380和1392平台进行了试验,并利用GPS对该试验平台进行高程测量及绘制高程3D图以评价根底率,结果发现改进后的爆破方案取得了良好效果,不但有效地降低了根底率,而且减少了炸药用量和钻孔工作量。多次重复试验结果显示,85%以上的平台均取得了良好的爆破效果,但是对于高程较低的平台如1284西帮南区平台,其爆破效果不甚理想,这可能是由于随着平台高程的降低,岩石完整性及强度提高,进而炮孔底部夹制作用变大,此时应加大钻孔超深。

马尾松和杉木人工林细根碳氮磷化学计量特征随土层深度的变化

为探究马尾松和杉木人工林细根碳(C)、氮(N)、磷(P)浓度及其化学计量比随土层深度变化的特征,于2011年4月在福建省三明市金丝湾森林公园陈大林业采育场内测定马尾松和杉木人工林五个土层深度(0—10 cm、10—20 cm、20—40 cm、40—60 cm、60—80 cm)细根的C、N、P浓度、比根长(SRL)及其土壤养分浓度,结果表明:林分类型显著影响细根C浓度,但对细根N、P浓度无显著影响,马尾松人工林细根C浓度显著大于杉木人工林。土层深度显著影响马尾松和杉木人工林细根N、P浓度,对C浓度无影响,细根N、P浓度随土壤深度的增加呈指数下降。马尾松和杉木人工林细根N、P浓度与土壤全氮(TN)、全磷(TP)浓度以及SRL均呈正相关。拟合直线表明马尾松人工林和杉木人工林细根N养分获取能力的不同,马尾松对N养分的获取能力更强,而杉木通过SRL获取养分的能力比马尾松更强,可能体现了两种人工林细根N获取策略的差异。马尾松和杉木人工林在不同土层细根N∶P比值(33.5±2.81、30.18±2.10)均大于16,表明两者均受P限制,但细根N∶P不受土壤N∶P和SRL的影响。马尾松和杉木人工林细根N和P浓度受土层深度的影响,与土壤养分和细根形态特征变化有关。