喀斯特坡地拉巴豆地埂篱根及根-土复合体力学特性

为探索地埂篱在喀斯特坡地水土保持中的价值,在重庆市酉阳县喀斯特顺层坡种植拉巴豆地埂篱,通过对根系灰度扫描、化学成分(木质素、纤维素、半纤维素)测定,单根抗拉试验和根-土复合体抗剪/冲试验,分析拉巴豆地埂篱根及根-土复合体的力学特性及影响因素。结果表明:(1)拉巴豆根系全根指标根长、根表面积、根体积、根重均表现为中坡下坡上坡,优势径级为0.0d≤1.0 mm径级。全根根系纤维素的平均含量较木质素、半纤维素高,且与根系直径呈显著负相关。(2)根系平均极限抗拉力6.77 N、平均抗拉强度29.57 MPa。极限抗拉力与木质素含量呈对数函数正相关、与木质素/纤维素(木纤比)呈线性正相关,抗拉强度与纤维素含量、木纤比分别为对数函数正相关和负相关。(3)上坡位抗剪土样的根体积密度、根重密度和木纤比显著大于中、下坡;而抗冲土样的根体积密度、根重密度、纤维素和半纤维素含量则中坡较优,但不显著。(4)根系能有效提高土体抗剪性能,根-土复合体的内摩擦角与粘聚力均较对照裸地高,但仅上坡粘聚力存在显著性差异(较对照增大45.67%)。内摩擦角和抗冲指数均中坡、下坡较优,粘聚力最优值位于上坡位。根-土复合体的力学特性主要受根体积、根重、根表面积密度和纤维素的影响。综上,拉巴豆根及根-土复合体的力学特性主要贡献径级为0.0d≤1.0 mm径级,中、下坡细根量大且根-土复合体抗冲性能表现较优,上坡根-土复合体抗剪切能力最强,但抗冲性能较弱。在推广拉巴豆地埂篱时,尽量种植于地势较低缓的中、下坡,更能凸显水土保持效益。     

三峡库区陡坡根-土复合体抗冲性能

以三峡库区已种植4a的紫花苜蓿、百喜草、狗牙根和香根草为对象,并以裸地为对照,采用改进的冲刷水槽、WinRHIZO(Pro.2004c)根系分析系统和应变控制式直剪仪,分析测定5个处理根-土复合体抗冲性能以及根系、土壤参数,以期揭示不同草本植物根系对陡坡地紫色土表土抗冲性能的强化效应。研究结果表明:与对照(裸地)相比,4种草本植物根系均能显著增强紫色土表土的抗冲性能,其中香根草根-土复合体的抗冲性能最强(为对照小区的2.75—3.58倍),而紫花苜蓿复合体的抗冲性能最弱(为对照小区1.96—2.60倍);草本植物根长密度(RLD)和根表面积密度(RSAD)是影响陡坡下紫色土表土抗冲性能的主要因子;0.50 mmd≤1.50 mm径级的根系有利于土壤抗冲性能的增强,尤其是1.00 mmd≤1.50 mm径级的根系对根-土复合体的抗冲性能强化效应最大;4种草本植物根系均有利于降低土壤容重、提高土壤有机质含量和增强土壤抗剪性能;土壤粘聚力c是影响根-土复合体抗冲性能的又一主要因子,径级1.00 mmd≤2.00 mm的根系则最有利于提高土壤粘聚力c。     

喀斯特槽谷区生态退化与修复专题导读

在国家重点研发计划项目——"喀斯特槽谷区土地石漠化过程及综合治理技术研发与示范(2016YFC0502300)"的支持下,经过项目组全体成员三年的共同努力,在喀斯特槽谷区生态退化与修复方面取得了一些重要进展。主要有:(1)2000—2015年槽谷区土壤侵蚀总量逐年减少,年平均侵蚀模数逐年降低,槽谷区植被覆盖明显提高;(2)拉巴豆地埂篱根土复合体不仅能有效提高喀斯特土壤的粒径大小和增强土体的抗剪/冲性能,并且能够利用大气N_2合成植物生长所需的氮肥,从而提高土壤肥力,可望实现石漠化治理中生态效应和经济效应的双赢;(3)喀斯特槽谷区隧道建设改变了地下水流场并降低了地下水位,进而降低了土壤微生物丰度和多样性,而增加了适应干旱的微生物种群,并导致土壤质量的降低;隧道建设加速了坡面产流和土壤流失,加剧了土地石漠化,从而导致生态退化;(4)随着槽谷区退化生态系统的恢复,生态系统的生态服务功能得到提升。     

公路边坡喷播绿化初期根系特征及其对抗剪强度的影响

植物根系对增强土体抗剪强度具有一定作用。为研究公路边坡喷播绿化初期根系特征及其对抗剪强度的影响,通过喷播的方式制备灌草混播试样,人工模拟边坡绿化7种灌草组合,植物生长3个月后进行原位剪切试验。挖取试样内植物根系,测定根系直径、根长密度、总表面积、总体积、根尖数、分叉数、根系密度、倾斜角度等根系特征指标,并通过灰色关联度法分析根系特征对土体抗剪强度的影响。结果表明:不同灌草混播组合根系特征随土层深度的变化存在一定差异;喷播绿化初期,0～2 mm细根占整个根系系统的96%～99%;水平根、侧根及垂直根分别占整个根系系统的7%～16%、44%～57%、33%～47%;不同灌草组合植物根系可增加土体抗剪强度6～17 k Pa,且不同灌草比试样抗剪强度大小依次为灌草比1∶1灌草比1∶4灌草比1∶5灌草比3∶1。灰色关联度分析结果表明,各根系指标对抗剪强度的影响大小依次为侧根数量水平根数量根系分布深度根系密度剪切面上部根长密度根长密度 0～2 mm细根数量剪切面下部根长密度总表面积总体积根尖数垂直根数量分叉数2～10 mm根系数量。该结果可为评价公路边坡喷播绿化初期坡体稳定性、指导边坡植被恢复提供依据。     

植物篱篱前淤积带与篱下土坎土壤水库和抗剪性能对比研究

为探究紫色土坡地植物篱篱前淤积带与篱下土坎处土壤贮水能力和抗剪性能的差异及变化规律，选取四川遂宁水土保持试验站10°新银合欢植物篱小区（L10）、10°香根草植物篱小区（V10）和15°香根草植物篱小区（V15），分上、中、下坡采集篱前淤积带和篱下土坎（无下坡）0-30 cm耕层土壤，测定土壤基本物理性质和土壤抗剪强度，计算土壤水库总库容、滞洪库容、内摩擦角φ和粘聚力c。结果表明：（1）同一篱带，篱前淤积带土壤保水贮水能力优于篱下土坎，其中篱前淤积带土壤自然含水率较之篱下土坎显著高6.52%-12.13%。（2）同一篱带，篱下土坎土壤透气性以及土壤抗剪性能均优于篱前淤积带，其中篱下土坎土壤非毛管孔隙度较之篱前淤积带显著高5.61%-57.70%。（3）同一小区，篱前淤积带保水贮水能力均表现为下坡 > 中坡 > 上坡，而篱下土坎均为上坡>中坡。其中V15小区上述趋势最明显，其下坡篱前淤积带（上坡篱下土坎）的土壤总库容和滞洪库容分别为上坡篱前淤积带（均为中坡篱下土坎）的1.04倍和1.03倍（1.02倍）。（4）同一小区，篱前淤积带土壤内摩擦角、粘聚力c和抗剪强度均表现为上坡 > 中坡 > 下坡，篱下土坎均为上坡>中坡。其中V10小区上述趋势最明显，其上坡篱前淤积带（上坡篱下土坎）上述指标依次为下坡篱前淤积带（均为中坡篱下土坎）的1.06、1.09倍和1.05倍（1.04倍）。（5）一个雨季前后篱前淤积带和篱下土坎土壤透气性、保水贮水能力及抗剪性能均无显著变化。     

三江并流区水电站消落带适生草本植物根系固土能力

三江并流区生态脆弱敏感,水电站库周消落带土壤侵蚀严重,为研究消落带适生草本植物的根系固土效应,并为重建植被、控制土壤侵蚀提供依据,以生长期为18个月的风车草(Cyperus alternifolius L.)、美人蕉(Canna indica L.)、花叶芦竹(Arundo donax var. versicolor)和菖蒲(Acorus calamus L.)4种草本植物为研究对象,采用自制的原位剪切仪测定根土复合体和素土的抗剪强度;用根系拉力试验机测定根系的抗拉强度,用Wu和Waldron模型(WWM)对根系提高土体抗剪强度进行预测,并评价模型的可靠性。结果表明：①4种适生草本植物根系都能增强土体的抗剪强度,风车草、美人蕉、花叶芦竹和菖蒲根系使土体的抗剪强度分别提高了403.89%、248.32%、388.50%和200.71%;②4种草本植物根系的抗拉强度均与直径呈现负幂函数关系;③根系抗拉强度较大、破坏面上根面积比较高和根系直径(D)<1 mm细根较多的草本植物,固土效应更加显著;④4种草本植物根系对土体强度增量的WWM模型计算值是实测值的9.37-43.85倍,该模型对高含水率土壤中草本植物根系的预测精度较低。风车草、美人蕉、花叶芦竹和菖蒲的根系均有较强的固土能力,尤其是风车草和花叶芦竹,是三江并流区黄登水库消落带植被重建和固土抗蚀的优选物种。     

浅层滑坡多发区典型灌木根系对边坡土体抗剪强度的影响

生态建设是"一带一路"可持续发展的基础,甘肃省陇南市位于"一带一路"核心区域,地处浅层滑坡多发区,地质灾害频发。通过单根抗拉试验和重塑土直接剪切试验对该区域四种典型灌木杠柳、胡枝子、酸枣和石榴的土壤及根系进行研究,探讨灌木根系对土壤物理性质和浅层滑坡的改善效应。结果表明,灌木根系能显著提高土壤含水率,改善孔隙结构;抗拉强度与根径间存在显著幂函数关系(P0.01),根径1 mm的毛细根抗拉强度最强,单根抗拉强度依次为胡枝子石榴酸枣杠柳;重塑土抗剪强度随土壤含水率升高而降低,土壤粘聚力(C)和内摩擦角(φ)均随含水率增加而减小,在10%的最优含水率下,抗剪强度依次为石榴酸枣杠柳胡枝子;随根系密度增加,杠柳和胡枝子的根-土复合体抗剪强度减小,酸枣和石榴在1.5倍天然根系密度下对土壤抗剪强度增强效果最强。通过评价浅层滑坡多发区不同灌木护土固坡效应,为"一带一路"沿线展开生态修复提供理论依据。     

黔中喀斯特木本植物功能性状变异及其适应策略

性状变异反映了植物的生活史对策。该研究以贵州普定县天龙山10种木本植物为对象, 通过分析枝叶和根系9个功能性状的种间与种内变异, 揭示植物对喀斯特生境的适应策略。结果表明: (1) 9个性状变异程度不同, 细根组织密度的种间和种内变异系数最大, 分别达96.47%和51.44%, 小枝干物质含量的种间与种内变异最小, 分别为11.67%和6.83%。(2)种间水平的细根组织密度在不同物种中没有显著的差异, 比根长、叶厚度、叶面积、比叶面积、叶干物质含量、叶组织密度、小枝干物质含量和小枝组织密度均表现出显著的差异。在种内, 比叶面积差异显著, 其他性状差异不显著。(3)绝大多数叶和枝性状间显著相关, 比根长与比叶面积显著负相关, 其他根系性状与枝叶性状相关性不显著。总之, 与同纬度非喀斯特地区植物相比, 普定喀斯特地区植物具有较小的叶面积和比根长度, 较大的叶干物质含量、叶组织密度等一系列有利于减小蒸腾和储存养分的功能性状组合, 这可能是其适应干旱贫瘠的喀斯特环境的主要生态策略。     

Variations of plant functional traits and adaptive strategy of woody species in a karst forest of central Guizhou Province,southwestern China

性状变异反映了植物的生活史对策。该研究以贵州普定县天龙山10种木本植物为对象, 通过分析枝叶和根系9个功能性状的种间与种内变异, 揭示植物对喀斯特生境的适应策略。结果表明: (1) 9个性状变异程度不同, 细根组织密度的种间和种内变异系数最大, 分别达96.47%和51.44%, 小枝干物质含量的种间与种内变异最小, 分别为11.67%和6.83%。(2)种间水平的细根组织密度在不同物种中没有显著的差异, 比根长、叶厚度、叶面积、比叶面积、叶干物质含量、叶组织密度、小枝干物质含量和小枝组织密度均表现出显著的差异。在种内, 比叶面积差异显著, 其他性状差异不显著。(3)绝大多数叶和枝性状间显著相关, 比根长与比叶面积显著负相关, 其他根系性状与枝叶性状相关性不显著。总之, 与同纬度非喀斯特地区植物相比, 普定喀斯特地区植物具有较小的叶面积和比根长度, 较大的叶干物质含量、叶组织密度等一系列有利于减小蒸腾和储存养分的功能性状组合, 这可能是其适应干旱贫瘠的喀斯特环境的主要生态策略。     

青杨人工林根系生物量、表面积和根长密度变化

在植物生长季节,采用钻取土芯法对秦岭北坡50年生青杨人工林根径≤2 mm和2～5 mm根系的生物量、表面积和根长密度进行测定.结果表明：在青杨人工林根系(＜5 mm)中,根径≤2 mm根系占总生物量的77.8%,2～5 mm根系仅占22.2%;根径≤2 mm根系表面积和根长密度占根系总量的97%以上,而根径2～5 mm根系不足3%.随着土层的加深,根径≤2 mm根系生物量、表面积和根长密度数量减少,根径2～5 mm根系生物量、表面积和根长密度最小值均分布在20～30 cm土层.≤2 mm根系生物量、表面积和根长密度与土壤有机质、有效氮呈极显著相关,而根径2～5 mm根系的相关性不显著.     

根系固土主导力学因素与差异性评价

为了探究影响根系固土的主导力学因素,并为侵蚀区固土抗蚀植物种的筛选提供部分依据。以3—4年生(4年生为主)5种内蒙古干旱、半干旱地区常见的水土保持植物:柠条(Caragana microphylla Lam.)、沙柳(Salix psammophila C.wang et Ch.Y.Yang)、沙地柏(Sabina vulgaris Ant.)、白沙蒿(Artemisia sphaerocephala Krasch.)、沙棘(Hippophae rhamnoides Linn.)为研究对象,针对春季土壤干旱和夏季暴雨(土壤湿润)两种自然条件,对影响5种植物根系固土的10项指标进行主成分分析。结果表明,根系抗拉力学特性是影响植物根系固土的主导力学因素,其次为根-土界面摩阻特性,最后是根-土复合体抗剪特性。在此基础上,从根系力学特性的角度出发,运用层次分析法对两个时期5种植物根系固土能力的差异性进行评价。在评价过程中,为了保证评价数据完整性,减小专家主观因素所带来的误差,使评价结果更具科学性,该文将两个时期主成分分析所得3个力学特性的方差贡献率作为权重。评价结果显示,根系固土指数为:春季土壤干旱时期,柠条(0.834)沙柳(0.330)沙地柏(-0.066)白沙蒿(-0.206)沙棘(-0.864);夏季暴雨时期分别为,柠条(0.876)沙地柏(0.218)沙柳(0.065)白沙蒿(-0.404)沙棘(-0.755)。5种植物中,柠条根系的抗拉力学特性显著优于其他植物,可作为干旱、半干旱地区固土抗蚀的重要参考树种。     

Influence of the food plants on the degree of parasitism of larvae ofHeliothis armigera byCotesia kazak

Influence of the food plants ofHeliothis armigera (Hb.) on the degree of parasitism by exotic parasiteCotesia kazak Telenga (Hymenoptera: Braconidae) was studied in cages in the laboratory on 7 food plants such as cotton (Gossypium hirsutum L.), tomato (Lycopersicon esculentum Mill), okra [Abelmoschus esculentus (L.) Moench], Dolichos (dolichos lablab L.), pigeonpea [Cajanus cajan (L.) Millsp.], Cowpea (Vigna unquiculata (L.) and chickpea (Cicer arietium L.). To determine the preference of the parasite 2 test methods were employed. In single plant choice test cotton was most preferred. Next in order of preference were tomato and okra. Dolichos, pigeonpea, cowpea and chickpea were least preferred. In multiple choice test, however, cotton and okra were preferred followed by tomato. Parasites were seen visiting these plants very frequently and high parasitism was recorded on these plants. Chick pea, pigeon pea, cowpea and Dolichos were the least preferred food plants. There appears to be some difference in fecundity as affected by some food plants. Exposure on okra, cotton and tomato resulted in higher cocoon production as compared to pigeonpea, Dolichos, cowpea and chickpea. There was, however, no difference in sex-ratio and longevity of the progeny as affected by food plants. This exotic parasite should be released first in crops such as cotton, okra and tomato on whichH. armigera is a very serious pest in India and elsewhere. Contribution No. 140/86 of the Indian institute of Horticultural Research, Bangalore-560 089     

Root Strength and Root Area Ratio of Forest Species in Lombardy (Northern Italy)

Forest vegetation is known to increase hillslope stability by reinforcing soil shear resistance and by influencing hydrologic conditions of soil. Although the importance of plant root systems for hillslope stability has received considerable attention in recent years, the quantification of such an effect needs more investigation. In this paper, we present a synthesis of the data gathered in the last 5 years for some species in different locations of the Alps and Prealps of Lombardy (Northern Italy) with the aim to increase our knowledge on root tensile strength and on Root Area Ratio distribution within the soil. Concerning root tensile strength we developed tensile strength–diameter relationships for eight species: green alder (Alnus viridis(Chaix) D.C.), beech (Fagus sylvatica L.), red willow (Salix purpurea L.), goat willow (Salix caprea L.), hazel (Corylus avellana L.), European ash (Fraxinus excelsior L.), Norway spruce (Picea abies (L.) Karst.) and European larch (Larix decidua Mill.). Results show a great variability among the different species and also for the same species. In general, however, root strength (in terms of tension) tends to decrease with diameter according to a power law, as observed by other Authors. Comparing the power law fitting curves for the considered species, it can be observed that they fall in a relatively narrow band, with the exception of hazel, which appears the most resistant. Concerning the evaluation of root distribution within the soil we estimated the Root Area Ratio (the ratio between the area occupied by roots in a unit area of soil) according to its depth for five species (beech, Norway spruce, European larch, mixed hazel and ash) in three locations of Lombardy. Results show that there is a great variability of root density for the same species well as for different points at the same locality. The general behaviour of root density, in any case, is to decrease with depth according to a gamma function for all the studied species. The results presented in this paper contribute to expanding the knowledge on root resistance behaviour and on root density distribution within the soil. The studied location have allowed the implementation of soil–root reinforcement models and the evaluation of the vegetation contribution to soil stability.     

Parasitoid-host relationship betweenTrioxys (Binodoxys) Indicus [Hymenoptera: Aphidiidae] andAphis Craccivora [Hemiptera: Aphididae]. VI. Impact of males on the number of progeny of the parasitoid reared on certain host plants

The present paper elucidates the impact of males on the reproductive rate ofTrioxys (Binodoxys) indicus reared on the aphids ofCajanus cajan, Dolichos lablab andSolanum melongena host plants. The F₁ offspring increases with the increase of parasitoid number. This increase is maximum inC. cajan followed byD. lablab andS. melongena reared aphids. The presence of male parasitoids caused a significant decrease in the emergence of F₁ generation.      

Flow cytometric analysis for ploidy level differentiation of 45 hairy vetch accessions

Determining the ploidy of plant germplasm is a necessary step in breeding or genetic studies in species. The purpose of this research was to determine the presence of ploidy level differentiation of hairy vetch (Vicia villosd) germplasm. Flow cytometry and root tip chromosome squashing methods were employed to assess 45 accessions labeled V. villosa available through the USDA germplasm collection. Flow cytometry determined that 43 of the accessions were 2C, one accession was 4C, and one accession was 6C. Analysis of accessions by root tip chromosome counts indicated that all accessions were diploid. The 2C accession contains 14 chromosomes and their chromosomes were approximately one-half and one-third in size as compared to the chromosomes of the 4C and 6C accessions, respectively. The 4C accession was observed to have 16 chromosomes and the 6C accession was observed to have 14 chromosomes. The large-scale differences in DNA amounts were due to chromosomal size variability as opposed to ploidy differences. This revealed the incidence of species misidentification of these two V. villosa accessions to be Vicia pannonica. All the V. villosa accessions were observed to be diploid and have similar DNA amounts. Flow cytometry proved to be useful in the efficient assessment of these accessions.     

Purification and Separation of Eight Steroidal Plant-growth Regulators from Dolichos lablab Seed

Purification and separation of eight steroidal plant-growth regulators, dolicholide, dolichosterone, homodolicholide, homodolichosterone, brassinolide, castasterone, 6-deoxocastasterone and 6-deoxodolichosterone, from immature seed of Dolichos lablab were accomplished using various chromatographic techniques. The reversed-phase HPLC of a number of steroidal plant growth regulators was also studied.     

Germination and Initial Root Growth of Four Legumes as Affected by Landfill Biogas Atmosphere

The most important problem in the restoration of closed landfills is the production of toxic gases by decomposition of refuse. Such gases affect the root system of plants growing on these sites. The aim of the present study was to assess the effects induced by landfill biogas contamination on germination and initial root growth of Vicia villosa (hairy vetch), Lotus corniculatus (birdsfoot trefoil), Trifolium pratense (red clover), and Trifolium repens (white clover). In laboratory conditions, simulated landfill and control gas were supplied to the seedlings. The composition of the simulated landfill gas used was: 16% O₂, 8% CO₂, 3% CH₄, and 73% N₂; a control gas was also tested (21% O₂, 0. 035% CO₂, and 78% N₂). Percentage of germinated seeds was determined after 6 and 12 days from the starting date; at the same time qualitative assays of metabolic root functionality were also performed by using an agar technique in order to visualize changes in rhizosphere pH. At the end of the experiment, the length of the primary and secondary root was measured. Germination after 6 days was affected by the gas treatment; the landfill biogas caused a delay in germination with respect to the control in seeds of V. villosa and L. corniculatus. Root fresh weight and dry weight were significantly decreased by biogas treatment in V. villosa and T. repens. In contrast, root dry weight was higher in gas treated L. corniculatus and T. pratense compared to control seedlings. Total root system was significantly higher in treated T. pratense. The qualitative assay suggests, with the exception of T. pratense, a metabolic adjustment of the treated seedlings. Key words: restoration, landfill biogas, legumes.     

Penetration of Crotalaria juncea,Dolichos lablab,and Sesamum indicum Roots by Meloidogyne javanica

Penetration of Crotalaria juncea (PI 207657 and cv. Tropic Sun) Dolichos lablab cv. Highworth, and Sesamum indicum by juveniles (J2) of Meloidogyne javanica was assessed to investigate the mechanism by which these plants may reduce nematode numbers in the field. Growth chamber experiments were conducted at 25 C, with vials containing 90 g sand infested with 450 J2; tomato (UC 204 C) was included as a susceptible host. Fifteen days after inoculation, roots were stained and the nematodes within stained roots were counted. Both C. juncea lines were highly resistant to penetration, as they contained significantly fewer nematodes per cm of root and per root system than the other plants. Although containing more nematodes per cm of root than C. juncea, S. indicum and D. lablab had significantly fewer nematodes per root system and per cm of root than tomato. Roots were significantly longer in the plants with the lowest nematode penetration. Although C. juncea, D. lablab, and S. indicum may have potential utility as cover or rotation crops in soil infested with M. javanica, further quantitative information on the reproduction of M. javanica and other nematodes in these plants is needed.     

Root tensile strength and root distribution of typical Mediterranean plant species and their contribution to soil shear strength

In Mediterranean environments, gully erosion is responsible for large soil losses. It has since long been recognized that slopes under vegetation are much more resistant to soil erosion processes compared to bare soils and improve slope stability. Planting or preserving vegetation in areas vulnerable to erosion is therefore considered to be a very effective soil erosion control measure. Re-vegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass in reducing water erosion rates, whereas the role of the below-ground biomass is often neglected or underestimated. While the above-ground biomass can temporally disappear in semi-arid environments, roots may still be present underground and play an important role in protecting the topsoil from being eroded. In order to evaluate the potential of plant species growing in Mediterranean environments to prevent shallow mass movements on gully or terrace walls, the root reinforcement effect of 25 typical Mediterranean matorral species (i.e. shrubs, grasses herbs, small trees) was assessed, using the simple perpendicular model of Wu et al. (Can Geotech J 16:19–33, 1979). As little information is available on Mediterranean plant root characteristics, root distribution data were collected in SE-Spain and root tensile strength tests were conducted in the laboratory. The power root tensile strength–root diameter relationships depend on plant species. The results show that the shrubs Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. have the strongest roots, followed by the grass Brachypodium retusum (Pers.) Beauv. The shrubs Nerium oleander L. and the grass Avenula bromoides (Gouan) H. Scholz have the weakest roots in tension. Root area ratio for the 0–0.1 m topsoil ranges from 0.08% for the grass Piptatherum miliaceum (L.) Coss to 0.8% for the tree Tamarix canariensis Willd. The rush Juncus acutus L. provides the maximum soil reinforcement to the topsoil by its roots (i.e. 304 kPa). Grasses also increase soil shear strength significantly (up to 244 kPa in the 0–0.1 m topsoil for Brachypodium retusum (Pers.) Beauv.). The shrubs Retama sphaerocarpa (L.) Boiss. and Anthyllis cytisoides L. are increasing soil shear strength to a large extent as well (up to 134 and 160 kPa respectively in the 0–0.10 m topsoil). Whereas grasses and the rush Juncus acutus L. increase soil shear strength in the topsoil (0–0.10 m) to a large extent, the shrubs Anthyllis cytisoides (L.), Retama sphaerocarpa (L.) Boiss., Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. strongly reinforce the soil to a greater depth (0–0.5 m). As other studies reported that Wu’s model overestimates root cohesion values, reported root cohesion values in this study are maximum values. Nevertheless, the calculated cohesion values are used to rank species according to their potential to reinforce the soil.