粤东铅锌尾矿区四种莎草的重金属富集特性研究

从梅州丙村铅锌尾矿区近污水排放区采集了土壤与四种优势植物样品, 分别测定和分析了Zn、Pb、Ni、Cu、Cr、Cd、Mn 七种重金属含量。结果表明, 该矿区土壤污染严重且为强酸性。Cd、Pb、Zn、Mn、Cu 的污染指数均大于3, 且综合污染指数为319.16, Zn、Pb、Cd 均超出国家土壤环境质量(GB15618-1995)的二级标准, 也远超过广东土壤背景值, 有很大的潜在生态风险, 重金属单因子生态风险指数大小排序为Cd>Pb>Zn>Mn>Cu>Ni>Cr。两歧飘拂草(Fimbristylis dichotoma)、细辐射枝藨草(Scirpus filipes)、多枝扁莎(Pycreus polystachyus)地下部分的Pb 含量均超过超富集植物临界含量标准, 因此这三种植物有作为Pb 富集植物的潜力。贝壳叶荸荠(Heleocharis chaetaria)对镍的富集系数超过1, 细辐射枝藨草对Mn 的转移系数大于1。这四种植物对土壤的重金属污染有很强的耐性, 与非矿区土壤中生长相比, 长势并无显著差异, 且地下部分重金属含量都很高, 说明对它们土壤中的重金属有一定的固定作用, 可作为这些区域植被恢复的先锋植物。     

封育对高寒草甸植物群落构成及生态位特征的影响

封育是天然草地管理的一种有效措施,利于草地生产力提高和退化草地恢复。该研究通过对青藏高原高寒草甸放牧和封育草地物种多样性、植被构成、植物种生态位特征、草地演替度等分析,解析高寒草甸植物种间关系及草地演替方向。结果表明:(1)封育显著降低了草地群落植物物种数以及α和β多样性指数,显著增加了草地1年生植物种数、地面芽植物种数和地上生物量。(2)放牧草地地上生物量以莎草科(59.7%)和禾本科(23.9%)为主,封育草地地上生物量以禾本科(85.0%)为主;放牧草地优势种为矮嵩草(Kobresia humilis)和线叶嵩草(K.capillifolia),封育草地优势种为垂穗披碱草(Elymus nutans)和早熟禾(Poasp.)。(3)放牧和封育草地的群落植物种重要值均与各自的生态位宽度变化规律一致。(4)草地植物种间竞争主要发生在不同科属植物种之间,封育增加了群落植物种整体生态位重叠值和植物种间竞争。(5)草地群落演替度为封育地放牧地,封育群落处于较稳定状态。研究认为,封育促进了高寒草甸由莎草+杂类草群落向禾草+杂类草群落演替。     

滨海盐渍土壤中不同类型盐生植物富集镉的效应

为了利用被镉污染的滨海盐渍土壤,通过实验对比分析3种不同类型盐生植物对盐渍土中镉的富集效应,以期初步探明不同类型盐生植物在镉污染盐渍土壤修复中的效果。选择的3种盐生植物类型是:聚盐盐生植物,泌盐盐生植物和避盐盐生植物。通过温室盆栽实验,将植物在不同镉含量的盐渍土壤中种植培养60 d,测定和分析不同类型盐生植物对镉的生物浓缩因子、转移系数以及植株内地上部分和根部生物量和镉含量的变化。结果表明,不同镉含量的土壤对碱蓬和芦苇的生长影响较小,对二色补血草的生长影响较大。不同镉含量的土壤中,芦苇地上部分镉的生物浓缩因子变化差异不显著,并且其地上部分吸收镉的百分率较高。碱蓬和芦苇的转移系数大于二色补血草的转移系数,并且碱蓬的转移系数在不同镉含量的土壤中变化不显著;二色补血草的转移系数随着土壤中镉含量的增加而显著增大。3种盐生植物中,碱蓬最具修复镉污染盐渍土壤的潜力,这可能和它是聚盐盐生植物的生理类型有关。芦苇整个植株的地上部分富集镉的总量在3种植物中是最高的,因此,芦苇在镉含量较低时也可以做为镉污染盐渍土壤的修复材料。     

曼陀罗和苍耳对污染土壤中镉的吸收与富集

目的:研究曼陀罗和苍耳对重金属镉的吸收与富集特征.方法:室外盆栽试验和室内原子吸收测定曼陀罗和苍耳体内的镉含量.结果:土壤中的镉刺激了植物的生长,曼陀罗和苍耳的生物量都比对照有所增加;曼陀罗和苍耳体内的镉含量随土壤中镉浓度的增加而增加;当土壤中镉浓度为100mg·kg-1时,曼陀罗地上部分富集系数为1.15,大于1,而在其它测试浓度下均小于1;苍耳地上部分的富集系数在所有测试浓度下都小于1.结论:曼陀罗和苍耳都不属于镉的超富集植物.     

四川甘洛铅锌矿区优势植物的重金属含量

通过野外调查采样,分析了四川凉山州甘洛县铅锌矿区土壤的重金属含量,以及矿区生长的13种优势植物对Pb、Zn、Cd、Cr、Cu的吸收与富集能力及其富集特性.结果表明,矿区土壤受Pb、Zn、Cd 3种重金属污染严重,13种植物体内的Pb含量均高于普通植物10倍以上,具有修复矿区土壤铅污染的潜力,其中植物1的转运系数和富集系数都大于1,满足Pb超富集植物的基本特征.Zn在凤尾蕨、细风轮菜、大火草、蔗茅、小飞蓬和牛茄子中含量较高.小飞蓬和紫茎泽兰的Cd含量较一般植物高出17～61倍,其中,紫茎泽兰的转运系数与富集系数均大于1,其对Cd的吸收特性值得进一步研究.     

5种湿地植物对土壤重金属的富集转运特征

选择芦苇、水葱、千屈菜、扁秆藨草、长苞香蒲5种湿地植物进行盆栽实验,比较它们对土壤中的5种重金属镉、铬、汞、铅、锌的富集特性,分析重金属在各植物体和土壤中的动态分布,以评价所测植物对土壤中重金属的综合富集能力,为利用植物修复金属污染土壤提供理论依据和技术支持。结果表明:(1)种植湿地植物对土壤重金属的富集效果显著高于无植物对照,且随着处理时间的延长,土壤中重金属镉、铬、汞、铅、锌的含量均呈下降趋势。(2)湿地植物对重金属镉、铬、汞、铅、锌的富集效果差异显著,其中水葱根部对重金属镉的富集系数最大,芦苇根部对重金属铬、汞、铅、锌的富集系数均最大,千屈菜、扁秆藨草和长苞香蒲根部对5种重金属的富集系数均较小;芦苇地上部分对金属镉的富集系数最大,千屈菜地上部分对金属铬、汞、铅的富集系数均最大,水葱地上部分对金属锌的富集系数最大。(3)5种湿地植物对重金属镉、铬、汞、铅、锌的转移系数差异显著,其中扁秆藨草对土壤中镉、铬、铅、锌的转移系数均为最大,对铬和锌的转移系数均大于1,长苞香蒲对铬的转移系数大于1,仅次于扁秆藨草。其他3种植物对5种重金属的转移系数均小于1。研究表明,5种湿地植物对重金属Cd、Cr、Hg、Pb、Zn都有富集和转移的能力,但不同植物对不同重金属的富集效果不同。     

不同放牧强度下高寒灌丛植物的生长特点

 不同放牧强度下高寒灌丛植物在生长发育、生理生态,物质生产和群落结构等方面主要有以下变化：1．在高寒灌丛草场,禾草类、莎草类和灌丛类植物的叶面积指数和平均生长速率随着放牧强度的减轻而增大;随着放牧强度的增加而减小。植株平均高度,植被盖度水平也与放牧强度呈负相关(p<0.01)。2．各项生长分析参数中：叶面积比率(LAR)、叶面积干重比(SLA)和叶干重比(LWR)与放牧强度之间存在负相关。叶面积指数(LAI)与地上生物量呈正相关(p<0.5),地上部现存在量与放牧强度呈负相关(p<0.01)。3．不同放牧强度条件下,高寒灌丛中的禾草类、莎草类、灌丛类和杂类草植物的种类组成和数量变化明显。其中禾草类和莎草类、灌丛类植物的生物量和种类组成比例在重度放牧下减少,在轻度放牧下增大。反之,重度放牧下杂类草的组成和数量明显增加,而轻度放牧下其比例降低。     

超富集植物短毛蓼对锰的富集特征

通过野外调查和营养液培养试验,研究了锰在短毛蓼体内的富集特征和对其生长的影响.在锰含量高达2.5×105mg/kg的锰矿废弃地上短毛蓼生长良好,叶锰含量高达1.66×104mg/kg.营养液培养条件下,随着生长介质中Mn浓度的升高,短毛蓼根、茎、叶中的Mn含量逐渐增加,当锰供应水平为1.000mmol/L时,叶锰含量超过10000mg/kg;当锰供应水平为20 000mmol/L时,短毛蓼仍能生长,根、茎和叶3部分的锰含量均达到最大值,分别为9923,18112mg/kg和55750mg/kg.在所有锰供应水平下,短毛蓼茎和叶中的锰含量都比根部的高.结果表明,短毛蓼是一种锰超富集植物,这一发现为锰污染土壤的植物修复和探讨锰在植物体内的超富集机理提供了一种新的种质资源.     

粤东铅锌尾矿三种优势植物对重金属的吸收和富集特性研究

为探讨铅锌矿废弃地优势植物在重金属污染土壤植物修复中的应用潜力,利用野外采样分析法,从粤东梅县丙村铅锌尾矿区采集其三种优势植物类芦、黄荆、盐肤木的根、茎、叶和土壤样品,测定和分析Pb、Zn、Cu、Cd四种重金属含量.结果表明:该矿区土壤污染严重,Pb、Zn、Cd含量远超土壤环境质量的三级标准,Cu超出二级标准;根际土壤和非根际土壤重金属含量均为Pb＞Zn＞Cu＞Cd,但根际土壤的重金属含量显著低于非根际土壤;这三种植物对Pb、Zn、Cu的转移系数大于1.0,对Cu的富集系数最高,Pb最小,但对四种重金属的富集系数均小于1.0,均未达到超富集植物临界含量标准.三种植物为该矿区的优势植物,说明它们对土壤的重金属污染有很强的耐性,虽然并非典型的超富集植物,但对污染土壤仍有较好的修复效果.     

灌丛化对黄土高原草地植物群落结构和地上生物量的影响

中国北方草地普遍出现灌丛化现象,灌丛化改变植物群落结构、植物多样性和生产力,直接影响着草地生态保护与可持续利用。该研究以黄土高原灌丛化草地为研究对象,通过植被调查,分析比较不同坡向的灌丛斑块与禾草斑块植物群落结构(物种组成、优势种及物种多样性)和地上生物量的差异。结果发现:(1)灌丛化草地不同坡向对物种多样性及地上生物量均无显著影响(P 0.1),但不同斑块植物群落结构(P=0.001)及地上生物量(P0.001)存在显著差异。(2)灌丛化草地共出现植物29种,其中禾草斑块有27种,灌丛斑块有18种;灌丛化显著改变了植物群落的物种组成,优势种由长芒草(Stipa bungeana)更替为矮脚锦鸡儿(Caragana brachypoda),且灌丛化降低了草地物种丰富度,增加了群落均匀度。(3)灌丛化显著改变了草地地上生物量,其中灌丛斑块地上生物量较禾草斑块地上生物量增加251.2 g·m~(-2),灌丛斑块中灌木/半灌木地上生物量提高了452.1 g·m~(-2),多年生丛生禾草减少了176.5 g·m~(-2),其余功能群植物的地上生物量减少了24.4 g·m~(-2)。(4)灌丛化过程(从禾草斑块—灌丛斑块)中,植物种丢失对地上生物量减少的影响较小,新增物种和群落优势种更替促进了灌木斑块地上生物量增加;虽然灌丛化导致草地地上生物量增加,但植物物种丰富度降低和优势种更替很有可能改变草地多样性和稳定性维持机制。     

Phytoremediation of Metal-Contaminated Soil in Temperate Humid Regions of British Columbia,Canada

The suitability of five plant species was studied for phytoextraction and phytostabilisation in a region with temperate maritime climate of coastal British Columbia, Canada. Pot experiments were conducted using Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue), Helianthus annuus L (sunflower), Poa pratensis L (Kentucky bluegrass) and Brassica napus L (rape) in soils treated with three different metal (Cu, Pb, Mn, and Zn) concentrations. The bio-metric characters of plants in soils with multiple-metal contaminations, their metal accumulation characteristics, translocation properties and metal removal were assessed at different stages of plant growth, 90 and 120 DAS (days after sowing). Lolium was found to be suitable for the phytostabilisation of Cu and Pb, Festuca for Mn and Poa for Zn. Metal removal was higher at 120 than at 90 days after sowing, and metals concentrated more in the underground tissues with less translocation to the aboveground parts. Bioconcentration factors indicate that Festuca had the highest accumulation for Cu, Helianthus for Pb and Zn and Poa for Mn.     

The Role of Metal Transport and Tolerance in Nickel Hyperaccumulation by Thlaspi goesingense Halacsy

Metal hyperaccumulators are plants that are capable of extracting metals from the soil and accumulating them to extraordinary concentrations in aboveground tissues (greater than 0.1% dry biomass Ni or Co or greater than 1% dry biomass Zn or Mn). Approximately 400 hyperaccumulator species have been identified, according to the analysis of field-collected specimens. Metal hyperaccumulators are interesting model organisms to study for the development of a phytoremediation technology, the use of plants to remove pollutant metals from soils. However, little is known about the molecular, biochemical, and physiological processes that result in the hyperaccumulator phenotype. We investigated the role of Ni tolerance and transport in Ni hyperaccumulation by Thlaspi goesingense, using plant biomass production, evapotranspiration, and protoplast viability assays, and by following short- and long-term uptake of Ni into roots and shoots. As long as both species (T. goesingense and Thlaspi arvense) were unaffected by Ni toxicity, the rates of Ni translocation from roots to shoots were the same in both the hyper- and nonaccumulator species. Our data suggest that Ni tolerance is sufficient to explain the Ni hyperaccumulator phenotype observed in hydroponically cultured T. goesingense when compared with the Ni-sensitive nonhyperaccumulator T. arvense.     

Carbon,nitrogen and phosphorus stoichiometry in leaves and fine roots of dominant plants in Horqin Sandy Land

Aims The stoichiometric characteristics of carbon (C), nitrogen (N) and phosphorus (P) in plant organism is vital to understand plant adaptation to environment. In particular, the correlations of elemental stoichiometric characteristics between leaf and fine root could provide insights into the interaction and balance among the plant elements, nutrient use strategies and plant response to global change.Methods We measured C, N, P contents and C:N, C:P, N:P in leaves and fine roots of 60 dominant plants in Horqin sandy land. The 60 plant species were classified into five life forms and two categories such as perennial forb, annual forb, perennial grass, annual grass, shrub, legume, and non-legume. We statistically analyzed the differences and correlations of C, N and P stoichiometry either between fine root and leaf or among five life forms.Important findings The average C, N and P concentrations in leaves of 60 plant species in Horqin sandy land are 424.20 mg·g^-1, 25.60 mg·g^-1 and 2.10 mg·g^-1, respectively. In fine roots, the corresponding element concentrations are 434.03 mg·g^-1, 13.54 mg·g^-1, 1.13 mg·g^-1. N and P concentrations in leaf are approximately twice as high as averages in fine root. Furthermore, similar N:P between leaf and fine root indicates conservative characteristic of elemental stoichiometry in plant organism, suggesting that nutrients distribution is proportional between aboveground and underground of plants. There are significant difference of C, N, P, C:N, C:P and N:P in leaf and root among five life forms. N and P in forb and C:N and C:P in grass are averagely higher than those in other life forms. N:P in annual forb and grass, however, are lower than those in other life forms. C, N in legume are higher than those in non-legume, while C:N in legume is lower than in non-legume. These results imply that nutrient use strategies are significantly different among plant life forms. Correlations analysis showed that N and P in leaf or fine root positively correlated, but C and N, C and P in fine root negatively correlated, suggesting coupling relationship among C, N and P in leaf and fine root. Subsequently, we detected positively significant correlations in C, N, P and their ratios between leaf and fine root, suggesting proportional distribution of photosynthate and nutrient between aboveground and underground during plant growth. Generally, these results supplied fundamental data to understand mass turnover and nutrients cycling of leaves and roots in sand land.     

Prospecting for hyperaccumulators of trace elements: a review

Specific plant species that can take up and accumulate abnormally high concentrations of elements in their aboveground tissues are referred to as “hyperaccumulators”. The use of this term is justified in the case of enormous element-binding capacity of plants growing in their natural habitats and showing no toxicity symptoms. An increasing interest in the study of hyperaccumulators results from their potential applications in environmental biotechnology (phytoremediation, phytomining) and their emerging role in nanotechnology. The highest number of plant species with confirmed hyperaccumulative properties has been reported for hyperaccumulators of nickel, cadmium, zinc, manganese, arsenic and selenium. More limited data exist for plants accumulating other elements, including common pollutants (chromium, lead and boron) or elements of commercial value, such as copper, gold and rare earth elements. Different approaches have been used for the study of hyperaccumulators – geobotanical, chemical, biochemical and genetic. The chemical approach is the most important in screening for new hyperaccumulators. This article presents and critically reviews current trends in new hyperaccumulator research, emphasizing analytical methodology that is applied in identification of new hyperaccumulators of trace elements and its future perspectives.     

Inbreeding depression and family variation in a social insect, Bombus terrestris (Hymenoptera: Apidae)

Arid and semi-arid ecosystems often exhibit diverse plant growth forms in water-limited environments, but it is unclear whether resource competition (interference) is actually important in structuring communities. We chose a diverse Chihuahuan desert shrubland to examine the response of the plant community to experimental removals of selected perennial plant species or groups of species. Four treatments involved the removal of all individuals of all species of a single functional group (functional group removals: shrub removal, succulent removal, subshrub removal, perennial grass removal). Three other treatments involved removing species within functional groups. These seven treatments plus a control (no plants removed) were replicated six times each in 25×25 m experimental plots, in summer 1995. Permanent belt transects were surveyed for number and sizes of all vascular plants in spring and fall in 1997, 1999, 2000, and 2001. Those plots from which the dominant shrub, Larrea tridentata , was removed had not recovered in total plant cover or volume by 2001, but cover and volume in all other treatments were similar to those in control plots. Relatively few species demonstrated a positive response to the removal of other species or functional groups. The perennial grass group and forbs were the most responsive; perennial grass cover increased in the shrub removal treatment relative to the control but treatment differences diminished after dry growing seasons in 2000 and 2001. Results over the first five years suggest that either environmental conditions or intrinsic biological characteristics limit the ability of most plant species to respond to the removal of substantial fractions of community biomass and composition in the short term. Such slow response by both dominant and less abundant components of the community has implications for the recovery of semi-arid systems after human disturbance or other events leading to the reduction of biological diversity.     

Plant population and community responses to removal of dominant species in the shortgrass steppe

Question: What are the plant population‐ and community‐level effects of removal of dominant plant species in the shortgrass steppe? Location: The Shortgrass Steppe Long‐Term Ecological Research site in northern Colorado, USA. Methods: We annually measured plant cover and density by species for 10 years after a one‐time aboveground removal of the dominant perennial grass, Bouteloua gracilis. Removal and control plots (3 m × 3 m) were within grazed and ungrazed locations to assess the influence of grazing on recovery dynamics. Our analyses examined plant species, functional type, and community responses to removal, paying special attention to the dynamics of subdominant and rare species. Results: Basal cover of B. gracilis increased by an average of 1% per year, but there was significantly less plant cover in treatment compared to control plots for 5 years following removal. In contrast to the lower cover in treatment plots, the plant density (number of plants m^?2) of certain subdominant perennial grasses, herbaceous perennial and annual forbs, a dwarf shrub, and cactus increased after removal of the dominant species, with no major change in species richness (number of species per 1 m × 1 m) or diversity. Subdominant species were more similar between years than rare species, but dominant removal resulted in significantly lower similarity of the subdominant species in the short term and increased the similarity of rare species in the long term. Conclusions: Removal of B. gracilis, the dominant perennial grass in the shortgrass steppe, increased the absolute density of subdominant plants, but caused little compensation of plant cover by other plants in the community and changes in species diversity.     

The potential of phytoremediation using hyperaccumulator plants: a case study at a lead-zinc mine site

Contamination with heavy metals is one of the most pressing threats to water and soil resources, as well as human health. Phytoremediation might potentially be used to remediate metal-contaminated sites. A major advance in the development of phytoremediation for heavy metal affected soils was the discovery of heavy metal hyperaccumulation in plants. This study applied several established criteria to identify hyperaccumulator plants. A case study was conducted at a mining area in the Hamedan province in the west central region of Iran. The results indicated that plant metal accumulation differed among species and plant parts. Plant species grown in substrata with elevated metal levels contained significantly higher metal levels. Using the most common criteria, Euphorbia macroclada and Centaurea virgata can be classified as hyperaccumulators of specific heavy metals measured in this study and they might potentially be used for the phytoremediation of contaminated soils.     

Regeneration of N.W. African Pinus halepensis forests following fire

Pinus halepensis forests of N.W. Algeria are subjected to frequent fires. During the fire the aboveground parts of plants are completely burned but only a few species are killed. Most perennial herb and shrub species survive owing to their underground organs and regenerate vegetatively in the next moist period. The semi-shrubs regenerate both vegetatively and from seeds. The most intensive growth of the shrub layer occurs during the first 2 years and in the 5th year, it reaches a height of 1–1.5 m. Pinus halepensis is completely killed by the fire and it regenerates from seeds only. The regeneration is retarded during the first 2–3 years, apparently by competition of the rapidly developing shrubs and semi-shrubs with P. halepensis. In the following years, there is a more rapid increase in both density and height, although by the 5th year after fire, the height does not exceed 0.5 m. The young trees overtop the shrub layer between 10 and 15 years after fire. The increase in density and cover supress the lower layers, in particular the herb layer. The reduction in density of trees in the following decades enables the herb layer to reconstitute its composition and cover.This process of regeneration resembles forest growth cycles rather than a secondary succession. The shrub and herb layers maintain their identity as they are mostly formed of the same individuals as before the fire; they merely regenerated their aboveground organs. Only the tree layer regenerates anew after the fire.     

Effects of selenium hyperaccumulation on plant-plant interactions: evidence for elemental allelopathy?

? Few studies have investigated plant-plant interactions involving hyperaccumulator plants. Here, we investigated the effect of selenium (Se) hyperaccumulation on neighboring plants. ? Soil and litter Se concentrations were determined around the hyperaccumulators Astragalus bisulcatus and Stanleya pinnata and around the nonhyperaccumulators Medicago sativa and Helianthus pumilus. We also compared surrounding vegetative cover, species composition and Se concentration in two plant species (Artemisia ludoviciana and Symphyotrichum ericoides) growing either close to or far from Se hyperaccumulators. Then, Arabidopsis thaliana germination and growth were compared on soils collected next to the hyperaccumulators and the nonhyperaccumulators. ? Soil collected around hyperaccumulators contained more Se (up to 266 mg Se kg(-1) ) than soil collected around nonhyperaccumulators. Vegetative ground cover was 10% lower around Se hyperaccumulators compared with nonhyperaccumulators. The Se concentration was higher in neighboring species A. ludoviciana and S. ericoides when growing close to, compared with far from, Se hyperaccumulators. A. thaliana showed reduced germination and growth, and higher Se accumulation, when grown on soil collected around Se hyperaccumulators compared with soil collected around nonaccumulators. ? In conclusion, Se hyperaccumulators may increase the surrounding soil Se concentration (phytoenrichment). The enhanced soil Se contents around hyperaccumulators can impair the growth of Se-sensitive plant species, pointing to a possible role of Se hyperaccumulation in elemental allelopathy.