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.

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.

Dynamic of Soil Microorganisms from Root Region of Ginseng with Different Growing Years

Objective To see the dynamic of fungi, bacilli and actinomyces communities from root region of ginseng with different growing years.Method With ginseng root region soils from several sampling sites of Jilin Province as materials, concentrations of fungi, bacilli and antinomyces were evaluated by spread-plate method. Result Though there are differences on statistic data among soil samples, commonly with the increasing of growing years, concentration of fungi in ginseng root region increased, which were on the contrary for bacilli and antinomyces, and bacilli changed even more significant than antinomyces. Conclusion Concentrations of soil microorganisms can be influenced by soil type, planting mode and growing years simultaneously, but growing years influenced even more significantly.

Influence of CO_2 Doubling on Water Transport Process at Root/Soil Interface of Pinus sylvestris var. sylvestriformis Seedlings

Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductance to survey soil water profiles and comparing it with root distribution surveyed by soil coring and root harvesting in Changbai Mountain in 1999. The results were: (1) The profiles of soil water content were adjusted by root activity. The water content of the soil layer with abundant roots was higher. (2) When CO 2 concentration was doubled, water transport was more active at the root/soil interface and the roots were distributed into deeper layer. It was shown in this work that the method of measuring electric conductance is an inexpensive, non_destructive and relatively sensitive way for underground water transport process.

Eco-geochemical Characteristics of Muskmelon Root Soil in Planting Region of Hetao Irrigation Area of Inner Mongolia

[Objective] The aim was to evaluate the eco-geochemical characteristics and geochemistry conditions of root soil in muskmelon planting area, evaluate the soil environment quality in Hetao irrigation area and provide scientific basis for the musmelon planting in this area. [Method] Root system soil sample and plow pan sample were collected from the main muskmelon planting area in Hetao irrigation area, so as to analyze the contents of heavy metal elements. By comparing with the Soft Environmental Quality Standard （GB15618-1995）, the research explored whether the heavy metal elements in root system met the national standard. [Result] Heavy metal elements in root system soil had the maximum content in recession area of Yellow River, followed by saline soils. The content of heavy metal elements in chestnut-brown soil was the minimum. Harmful elements As, Cd, Hg, F and Pb in anthropogenic-alluvial soil of Hetao irrigation area showed enrichment characteristics in earth surface, with zonality vertically. Trace elements Cu and Zn, and beneficial elements P, K20, CaO, MgO and Se showed depletion. In anthropogenic-aUuvial soil of Ulansuhai of the Yellow River, harmful elements As and Cd showed significant enrichment in root system soil, while other elements showed depletion or was close to background value. In soil of plow pan, both beneficial component and harmful component showed enrichment characteristics. [Conclusion] Hetao irrigation area has the ideal geochemical conditions and heavy metal elements in muskmelon area meet the national standards.

Influence of the roots of mixed-planting species on the shear strength of saline loess soil

In order to improve our knowledge of the mechanical effect of the roots of mixed-plantings on soil reinforcement and slope protection,the influence of roots of a mixed-planting with four herb species(Medicago sativa L.,Elymus nutans Griseb.,Puccinellia distanx(L.),and Poa pratensis L.)and one shrub species(Caragana korshinskii Kom.)were investigated on the shear strength characteristics of saline loess soil.The root distribution characteristics were assessed via a survey when the plants grew for one year.The effects of the root biomass density,the root mass ratio(RMR)of the fine roots to the coarse roots,the moisture content,and the salt content on the shear strength index of the rooted soil were analyzed via a triaxial compression test,and the mechanism of these effects was discussed.The results indicate that the biomass density decreased linearly with increasing depth.The RMR initially decreased with depth and then increased,exhibiting in a quadratic relationship.The cohesion of the rooted soil increased linearly as the biomass density increased.The cohesion of the rooted soil initially increased with increasing RMR and salt content,and then it decreased.The turning point of the cohesion occurred when the RMR was 0.6 and the salt content was 1.18%.The internal friction angle of the rooted soil initially increased with biomass density and then decreased,and the turning point of the internal friction angle occurred when the biomass density was 0.015 g/cm3.The relationships between the internal friction angle of the rooted soil and the RMR and salt content were exponential incremental and linear subtractive relationship,respectively.Both the cohesion and the internal friction angle of the rooted soil linearly decreased with increasing moisture content.

Estimation of soil reinforcement by the roots of four postdam prevailing grass species in the riparian zone of Three Gorges Reservoir, China

Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density（RLD） and root area ratio（RAR） were measured by using the Win RHIZO image analysis system. Root tensile strength（TR） was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu＇s perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers（＆gt;10 cm）. RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides（62.26MPa） followed by C. dactylon（51.49 MPa）, H.compressa（50.66 MPa）, and H. altissima（48.81MPa）. Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa（21.1 k Pa）, P.paspaloides（19.5 k Pa）, and C. dactylon（15.4 k Pa） at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.

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.

Firm Roots in Tibetan Soil

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中国南北方植物对土壤加固机制的差异性

为深入分析植物对土壤加固的影响效益和机制,该研究选取重庆缙云山地区和陕西延安黄土丘陵区种植一年的乔木(火炬树、榆树)和灌木(荆条、酸枣),测定其根系形态、力学参数和土壤的抗剪强度,通过RBMw模型计算根系固土效益,综合评估不同植物的固土效能和贡献度。结果表明:2地种植的物种平均根直径的差异不显著(P>0.05),重庆种植的乔木(火炬树、榆树)的根长、分叉数和根尖数显著高于延安,灌木未出现显著差异(P<0.05)。根系的抗拉强度与直径都符合负幂函数关系,其中平均抗拉强度最大的为荆条。除荆条外,同种植物根系的抗拉强度并未因不同地区的种植产生显著差异。4个植物种根系的固土效率为0.65~4.12 kPa,各物种间存在显著差异(P<0.05)。重庆2种乔木种植下的根土复合体有效黏聚力高于裸地(约10%),灌木种植下则普遍略低于裸地。除酸枣外,种植于重庆的4种植物的根系固土作用和效率都显著的高于延安(P<0.05)。研究结果可为不同地区固土护坡的树种选择提供理论依据。

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

The pot experiments were conducted in the artificial climate laboratories to determine the relativeimportance of mass flow and diffusion in supplying Fe, Mn, Cu and Zn to wheat, soybean and maize plantsgrowing in loessal soil and lou soil. It was found that the calculated relative contribution of mass flow ofiron, manganese, copper and zinc to plant uptake varied from 5% to more than 100%,depending on the cropspecies and soil types as well as plant growth stage, soil moisture, atmosphere humidity, etc. The results alsoshowed that the major transportation mechanisms of these micronutrients in soil-root system varied with thecrop and its growth, climate and soil, significantly. In general, mass flow was more important for Cu andZn and diffusion was more significant for Fe and Mn at the seedling stage.

Analysis for Soil Characteristics of Degraded Grassland on Alpine Meadow

[Objective]The aim of this study is to explore the effects of grassland degradation on soil physical and chemical properties.[Method]The ratio of plant root to soil and soil texture on Alpine Meadow were investigated in this study,and soil available N,P,K,Cu,Zn,organic matter and pH value were also analyzed by routine analysis of soil nutrients in different degraded grasslands.[Result]With the intensification of degraded gradient and the soil depth,the ratio of plant root to soil was decreased gradually.The highest ratio of plant root to soil was in 0-10 cm depth of soil in grassland with different degraded gradients,while its ratio of plant root to soil changed from 0.001 to 0.040 with soil type of loam.Soil chemical characteristic changed in different degraded gradients.The content of available N,P,K reduced significantly with the soil depth and the intensification of degraded gradients.The content of Cu and Zn was relatively lack in degraded grassland.[Conclusion]There is no significant correlation between nutrition content or pH value and the succession degree of degraded grassland.

北麓河青藏公路沿线多年冻土区热融滑塌型边坡植被防护力学效应研究

为评价青藏公路沿线多年冻土区高寒草甸和人工种植植物固土护坡力学贡献,本研究选取位于青藏公路沿线北麓河地区一处热融滑塌灾害作为研究区。以原生草甸(主要植物种为嵩草(Carex myosuroides Vill.)和藏嵩草(Kobresia tibetica Maxim.))和人工种植垂穗披碱草(Elymus nutans Griseb.)、星星草(Puccinellia tenuiflora(Griseb.)Scribn.&Merr.)、冰草(Agropyron cristatum(L.)Gaertn.)、早熟禾(Poa annua L.)、碱茅(Puccinellia distans(L.)Parl.)和中华羊茅(Festuca sinensis Keng ex S.L.Lu)等6种生长期为1 a草本为研究对象,通过开展室内原状根-土复合体剪切试验,探讨了草本根系增强热融滑塌型边坡体抗剪强度作用贡献,并采用静力平衡法对该热融滑塌型边坡稳定性进行了评价。主要得到如下结果:通过室内洗根试验得到根-土复合体试样平均含根量由高至低依次为原生草甸(33.33 mg·cm^(-3))、垂穗披碱草(16.95 mg·cm^(-3))、早熟禾(13.12 mg·cm^(-3))、中华羊茅(5.80 mg·cm^(-3))、冰草(3.89 mg·cm^(-3))、星星草(3.15 mg·cm^(-3))、碱茅(2.86 mg·cm^(-3));平均株高由高至低依次为垂穗披碱草(10.93 cm)、原生草甸(9.64 cm)、冰草(6.88 cm)、早熟禾(5.22 cm)、中华羊茅(3.90 cm)、碱茅(3.86 cm)、星星草(2.90 cm);区内原生草甸和6种人工种植草本根-土复合体抗剪强度均显著高于不含根系素土,其中原生草甸和人工种植垂穗披碱草根系增强土体抗剪强度作用增幅相对较大,分别为42.17%和30.96%;由静力平衡法计算得到含根系边坡安全系数均高于不含根系素土边坡,边坡安全系数由大至小依次为原生草甸(1.47)、垂穗披碱草(1.39)、早熟禾(1.38)、冰草(1.37)、碱茅(1.36)、星星草(1.32)、中华羊茅(1.32)、素土(0.96)。该研究结果对于有效防治青藏公路沿线北麓河地区热融滑塌灾害,同时为进一步有效防治青藏公路沿线热融滑塌灾害引发的水土流失、草地退化等灾害提供理论依据和实际指导。

毛乌素沙地不同植被恢复类型的土壤碳水效应

[目的]探讨不同植被恢复类型下土壤有机碳和水分含量特征及其关系,为毛乌素沙地植被恢复类型的选取提供科学依据。[方法]以毛乌素沙地自然恢复草地及沙蒿、沙柳、沙蒿×沙柳(灌灌混交)、樟子松、沙柳×樟子松(乔灌混交)为研究对象,并以裸沙地为对照,分析不同植被恢复类型对0-5.0 m土层土壤剖面碳、水的影响及其相关性。[结果](1)植被恢复增加土壤有机碳含量,沙柳×樟子松、樟子松、草地、沙蒿×沙柳、沙柳、沙蒿依次降低,0—0.2 m土层显著高于深层,表现为表聚效应;随着土层深度的增加,各植被类型的有机碳含量逐渐降低;沙蒿、沙柳、沙蒿×沙柳在0.8—2.2 m土层范围内表现为碳损失。(2)不同植被恢复类型在深层均存在不同程度的水分亏缺,主要集中在1.0—3.0 m土层,具体亏缺程度为沙柳×樟子松>樟子松>沙蒿×沙柳>沙柳>草地>沙蒿。(3)根系是影响土壤有机碳含量和水分消耗的主要因素;土壤有机碳含量与土壤含水量在0—5.0 m土层范围内负相关。[结论]植被固存有机碳以消耗深层土壤水分为代价,沙柳×樟子松固定同等单位量的碳消耗水分最少。因此,从土壤固碳和保水2个角度同时考虑,沙柳×樟子松在毛乌素沙地的植被恢复中具有较好的恢复效果。

紫穗槐接种AM真菌对红壤林下侵蚀劣地的影响研究

为探究植被接种丛枝菌根(AM)真菌对南方红壤区林下侵蚀劣地恢复的影响机制,本研究以马尾松退化林地为对象,设置引种灌木不接菌(S)和引种灌木接菌(S+AMF)两种处理,研究土壤AM真菌群落、土壤肥力及植物生长对紫穗槐(Amorpha fruticosa L.)接种AM真菌的响应。结果表明,接菌一年后,S+AMF处理菌根侵染率(MIR)极显著大于S处理(P<0.001),而接菌三年后MIR在两处理间无显著差异。接菌三年后,与S处理相比,S+AMF处理AM真菌的多样性和丰富度无显著差异,但其在种水平上的网络复杂性有所提高,其中Rhizophagus manihotis、Glomus cf.clarum Att894-7、fungal sp.Kamogawa和Rhizophagus neocaledonicus丰度具有显著性差异;土壤有机碳(SOC)、全氮(TN)、总球囊霉素相关土壤蛋白(TG)、土壤微生物生物量碳(SMBC)和土壤微生物生物量氮(SMBN)含量均显著或极显著提高,土壤团聚体变化不显著;植物叶片中全氮(TN)和全磷(TP)含量以及地上生物量(AGB)均显著或极显著提高,而地下生物量(UGB)显著降低(P<0.05);植物根系构型中,根系总根长(TRL)、总体积(TRV)、比根长(SRL)、比表面积(SSA)和根冠比(R-S R)均显著或极显著降低,而根组织密度(RTD)则极显著提高(P<0.001)。线性回归分析表明,SOC、土壤TN、TG、SMBC、SMBN、AGB与MIR间存在显著或极显著正相关关系,TRL、TRV、R-S R、UGB和MIR间存在显著或极显著负相关关系,说明紫穗槐接种AM真菌能够有效改善土壤肥力,同时改变植物地上地下部的生长情况。本研究结果为林下劣地土壤质量提升和植被恢复提供了技术参考。

甘蔗/花生间作对根系生理及根际土壤养分的影响

为探明甘蔗/花生间作对根系生理及根际土壤养分的影响,本文设置了甘蔗单作、花生单作、甘蔗/花生间作模式,系统分析了不同种植模式下根系分泌物、根系浸提物和根际土壤养分的变化及其相关性。结果表明:间作甘蔗根系分泌的总氨基酸及根系浸提液中的总糖显著高于单作,间作花生根系分泌的总糖显著高于单作。间作甘蔗根际土壤的碱解氮(alkali-hydrolyzed nitrogen,AN)、有效磷(available phosphorus,AP)、速效钾(available potassium,AK)和土壤有机质(soil organic matter,SOM)显著高于单作甘蔗,间作种植显著降低了花生根际土壤的有效磷、速效钾和pH。间作和单作甘蔗的酸性磷酸酶、过氧化氢酶、脲酶和蔗糖酶差异不显著,间作花生的过氧化氢酶显著高于单作花生。根系分泌的酚酸与土壤有机质呈显著负相关,总糖与蔗糖酶呈显著正相关,氨基酸与脲酶呈显著正相关;根系浸提液中的有机酸与pH呈显著正相关,氨基酸与SOM呈显著负相关、与AK呈极显著负相关。脲酶与AK呈显著负相关,蔗糖酶与SOM呈极显著负相关。综上,甘蔗/花生间作主要影响根系分泌氨基酸、总糖和酚酸的代谢活动,且可显著提高甘蔗的土壤有效养分。

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。