Role of herbaceous plant communities in biogenic cycles of chemical elements

The role of ecological factors in the formation of biogenic cycles of chemical elements has been studied. It has been shown that, both under background conditions and chemical pollution, biogeochemical and biocenotic factors contribute to this process. These are the species structure of a community, specific features of chemical element accumulation, biomass of individual species, and productivity of phytocenosis. The accumulation of chemical elements in the phytomass depends not so much on their increasing concentrations in the soils as on degradation of the environment caused by their toxic effect and manifested in transformation of species composition and reduction of the total phytomass of the phytocenosis.     

Role of Extrinsic Arbuscular Mycorrhizal Fungi in Heavy Metal-Contaminated Wetlands with Various Soil Moisture Levels

This study presents an efficient heavy metal (HM) control method in HM-contaminated wetlands with varied soil moisture levels through the introduction of extrinsic arbuscular mycorrhizal fungi (AMF) into natural wetland soil containing indigenous AMF species. A pot culture experiment was designed to determine the effect of two soil water contents (5–8% and 25–30%), five extrinsic AMF inoculants (Glomus mosseae, G. clarum, G. claroideum, G. etunicatum, and G. intraradices), and HM contamination on root colonization, plant growth, and element uptake of common reed (Phragmites australis (Cav.) Trin. ex Steudel) plantlets in wetland soils. This study showed the prevalence of mycorrhizae in the roots of all P. australis plantlets, regardless of extrinsic AMF inoculations, varied soil moisture or HM levels. It seems that different extrinsic AMF inoculations effectively lowered HM concentrations in the aboveground tissues of P. australis at two soil moisture levels. However, metal species, metal concentrations, and soil moisture should also be very important factors influencing the elemental uptake performance of plants in wetland ecosystems. Besides, the soil moisture level significantly influenced plant growth (including height, and shoot and root dry weight (DW)), and extrinsic AMF inoculations differently affected shoot DW.     

电子废弃物拆解区土壤重金属污染对丛枝菌根真菌多样性的影响

【背景】电子废弃物拆解造成的土壤重金属污染引发的环境问题日益突出,丛枝菌根(arbuscular mycorrhizal,AM)真菌能侵染植物根系并增强植物抵御环境胁迫的能力,具有重要的生态功能和应用潜力。【目的】探究电子废弃物拆解区土壤重金属污染对AM真菌群落结构与多样性的影响,甄别可耐受重金属污染的AM真菌类群。【方法】从浙江台州某典型电子废弃物拆解场地及其周边区域共采集土壤样品12份,针对土壤中AM真菌的18S rRNA基因进行高通量测序以及可操作分类单元(operational taxonomic unit,OTU)相对丰度和多样性指数计算。【结果】该区土壤中AM真菌由原囊霉目(Archaeosporales)、球囊霉目(Glomerales)和多孢囊霉目(Diversisporales)组成,其中球囊霉目占据优势地位。土壤AM真菌多样性指数与重金属的浓度、综合污染指数和潜在生态风险指数间均无显著相关性,但疑似泡囊根生囊霉(Rhizophagus vesiculiferus)的OTU相对丰度与上述重金属污染指标之间均呈显著正相关关系。【结论】R. vesiculiferus可能对重金属污染有极强耐受性,可为今后电子废弃物拆解污染土壤治理提供技术基础。     

工业运输活动对周边荒漠草原植物多样性与土壤性状的影响

研究工业运输活动释放出的重金属元素对周边荒漠草原植被群落特征和土壤性状的关系，为工业活动影响下的荒漠草原植被恢复和重建提供科学依据。以宁夏盐池县高沙窝工业集中区邻近的荒漠草原为研究对象，结合前期土壤和降尘的重金属含量，根据内梅罗污染指数划分了五个污染梯度(梯度Ⅰ、梯度Ⅱ、梯度Ⅲ、梯度Ⅳ和梯度Ⅴ),采用野外调查和室内分析的方法，对比分析了不同污染梯度下的植被群落特征与土壤性状的关系。结果显示：在前三个污染梯度下物种组成相对较多，禾本科(Gramineae)、藜科(Chenopodiaceae)、豆科(Leguminosae)和菊科(Compositae)为优势科。其中，牛枝子(Lespedeza potaninii)和短花针茅(Stipa breviflora)的重要值分别为59.41和44.26,是研究区工业生产和交通运输影响下的主要物种。随着污染梯度的升高，植物群落均匀度指数显著下降(P<0.05),工业交通运输活动造成研究区荒漠草原植被组成单一，群落结构不稳定。表层土壤养分受重金属影响波动较大，土壤全氮和有机质是影响物种多样性指数的主要土壤因子，随着污染梯度的升高显著降低(P...     

Simulation of phytomass productivity based on the optimum temperature for plant growth in a cold climate

During long-term monitoring (more than 20 years) of the hydrologic regime at 20 mountainous sites in the Czech Republic (altitude 600–1400 m a.s.l.; vegetation season April-September; mean air temperature 8–10°C; mean total precipitation 400–700 mm; mean duration of sunshine 1100–1300 hours; mean potential transpiration 200–250 mm) it was found that plant temperature does not rise above about 25°C when plants transpire. According to the ecological optimality theory, the phytocenosis that is able to survive unfavourable conditions and produce the biggest amount of phytomass will prevail at sites occurring in long-term stable natural conditions. Simulation of phytomass productivity based on the optimum temperature for plant growth showed that plants with an optimum leaf temperature of about 25°C can survive the unfavourable conditions and produce the largest amount of phytomass at the site studied in the long-term.     

Heavy metal contamination of soil and tree-ring in urban forest around highway in Shanghai,China

The heavy metal (HM) pollution of forest soil has been known as one of the most challenging pollution issues due to their characteristics. In order to know the HM pollution condition in urban forest, identify the possible source of HM, 102 sub-samples of soil in 34 sites and 39 tree rings sub-samples in 7 sites were collected in the outer-ring greenbelt (ORG) in Shanghai, China. Concentrations of Cu, Zn, Pb, and Cd in soil and tree rings were analyzed, and the soil properties pH, total nitrogen, total phosphorous, and organic matter were analyzed too. Geo-accumulation index and potential ecological risk index were used for assessing the contamination level of HMs. Nonparametric tests, one-way analysis of variance, correlation analysis, and principal component analysis were applied. The results showed that: (1) concentrations of Cu, Zn, and Cd in soil were significantly higher than their corresponding background values of Shanghai (BVs); concentrations of Cu, Zn, and Pb in tree rings increased gradually in the past 10 years; (2) Zn and Cd were in unpolluted to moderately polluted level, Cd has moderate degree potential ecological risk; (3) vehicle exhausts and abrasion of vehicle parts of tires and historical agricultural activities were the main sources of HM contamination; (4) Cinnamomum camphora (L.) Presl. has the potential to reconstruct the change of Cu, Zn, and Pb as a bioindicator. In conclusion, Cd should be considered as a priority control component. The relationship between plant and soil should take further focus and more studies of the behavior of HMs in soil and plants are required.     

Disentangling the mechanisms behind winter snow impact on vegetation activity in northern ecosystems

Although seasonal snow is recognized as an important component in the global climate system, the ability of snow to affect plant production remains an important unknown for assessing climate change impacts on vegetation dynamics at high‐latitude ecosystems. Here, we compile data on satellite observation of vegetation greenness and spring onset date, satellite‐based soil moisture, passive microwave snow water equivalent (SWE) and climate data to show that winter SWE can significantly influence vegetation greenness during the early growing season (the period between spring onset date and peak photosynthesis timing) over nearly one‐fifth of the land surface in the region north of 30 degrees, but the magnitude and sign of correlation exhibits large spatial heterogeneity. We then apply an assembled path model to disentangle the two main processes (via changing early growing‐season soil moisture, and via changing the growth period) in controlling the impact of winter SWE on vegetation greenness, and suggest that the “moisture” and “growth period” effect, to a larger extent, result in positive and negative snow–productivity associations, respectively. The magnitude and sign of snow–productivity association is then dependent upon the relative dominance of these two processes, with the “moisture” effect and positive association predominating in Central, western North America and Greater Himalaya, and the “growth period” effect and negative association in Central Europe. We also indicate that current state‐of‐the‐art models in general reproduce satellite‐based snow–productivity relationship in the region north of 30 degrees, and do a relatively better job of capturing the “moisture” effect than the “growth period” effect. Our results therefore work towards an improved understanding of winter snow impact on vegetation greenness in northern ecosystems, and provide a mechanistic basis for more realistic terrestrial carbon cycle models that consider the impacts of winter snow processes.     

Heavy Metal Contamination in the Brownfield Soils of Cleveland

The results esults of a survey of heavy metal contamination at Cleveland area brownfields and public spaces are presented. Soils were analyzed using a 24?h, 1N HCl extraction procedure. The study was conducted to seek brownfield soils that manifest properties of “old” sequestered contamination and to develop a better understanding of the nature and extent of heavy metal burdens at brownfield sites in the Greater Cleveland area. The results indicated that Cleveland brownfields commonly yield soil burdens well above remediation triggers for residential soils and often yield values above industrial remediation triggers. It was also discovered that public areas in the vicinity of brownfields commonly have heavy metal contamination significantly above background levels and occasionally above residential remediation triggers. These results indicate that brownfields redevelopment initiatives should proceed with caution. The appropriate remediation goals or restrictions must be imposed to control urban exposure to heavy metal contamination.     

城市化对土壤环境的影响

城市化对土壤环境产生深刻影响,城市污水灌溉、工业废气和汽车废气、城市生活垃圾等都会改变土壤的理化性质。防治土壤污染、改善城市土壤环境,必须工业合理布局,治理工业污染源,加强农业环境的监测等。     

Mechanisms of plant and microbial adaptation to heavy metals in plant–microbial systems

The data on heavy metal (HM) accumulation and detoxification by plants and bacteria in plant–microbial systems (PMS) are reviewed. Bacteria are shown to be the labile component of the system, responsible for a considerable amelioration of HM stress impact on plants and for improved PMS adaptation to heavy metals. Simulation of plant–microbial interactions under conditions of soil contamination by HM revealed the protective role of bacterial migration from the rhizoplane to the rhizosphere.     

城市化对土壤环境的影响

城市化对土壤环境产生深刻的影响,城市污水灌溉、工业废气和汽车废气、城市生活垃圾等都会改变土壤的理化性质。防治土壤污染、改善城市土壤环境,必须工业合理布局,治理工业污染源,加强农业环境的监测等。     

Abundance and Diversity of Ammonia-Oxidizing Prokaryotes in the Root–Rhizosphere Complex of Miscanthus × giganteus Grown in Heavy Metal-Contaminated Soils

Mine wastes have been considered as a source of heavy metal (HM) contamination in the environment and negatively impact many important ecosystem services provided by soils. Plants like Miscanthus, which tolerate high HM concentrations in soil, are often used for phytoremediation and provide the possibility to use these soils at least for the production of energy crops. However, it is not clear if plant growth at these sites is limited by the availability of nutrients, mainly nitrogen, as microbes in soil might be affected by the contaminant. Therefore, in this study, we investigated in a greenhouse experiment the response of ammonia-oxidizing microbes in the root–rhizosphere complex of Miscanthus × giganteus grown in soils with different levels of long-term arsenic (As) and lead (Pb) contamination. Quantitative PCR of the ammonia monooxigenease gene (amoA) was performed to assess the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) at two different points of plant growth. Furthermore, bulk soil samples before planting were analyzed. In addition, terminal restriction fragment length polymorphism (T-RFLP) analysis was used to investigate the diversity of archaeal amoA amplicons. Whereas high concentrations of As and Pb in soil (83 and 15?g/kg, respectively) resulted independent from plant growth in a clear reduction of AOA and AOB compared to the control soils with lower HM contents, in soils with contamination levels of 10?g/kg As and 0.2?g/kg Pb, only AOB were negatively affected in bulk soil samples. Diversity analysis of archaeal amoA genes revealed clear differences in T-RFLP patterns in response to the degree of HM contamination. Therefore, our results could clearly prove the different response patterns of AOA and AOB in HM-contaminated soils and the development of archaeal amoA phylotypes which are more tolerant towards HMs in soil samples from the areas that were impacted the most by mining waste, which could contribute to functional redundancy of ammonia-oxidizing microbes in soils and stability of nitrification pattern.     

Spectral response characteristics and identification of typical plant species in Ebinur lake wetland national nature reserve (ELWNNR) under a water and salinity gradient

The spectral characteristics of variable selection are particularly important for wetland vegetation mapping. In the present study, we combined soil salt and water content with spectral data collected in the Ebinur Lake Wetland National Nature Reserve (ELWNNR) in Western China to understand the effects of soil salt and water content on plant spectra. The results showed the following: (1) the distribution of plants reflect the macroscopic response characteristics of plants on water and salt environment; (2) a certain response rule exists between the spectra of different plants under a water and salt gradient, e.g., with increase in water and salt gradient, the spectral reflectivity of salt-dilution plant decreases, and salt-exclusion plant increases; (3) a response pattern is formed between the “trilateral” characteristics of plant spectrum and water salt gradient. With the increase of salinity gradient, the “red edge”, “blue edge”, and “yellow edge” shows the most obvious changes in the 0.8 order derivatives, e.g., when the soil salt content was range from 4.2 to 8.8 g/kg, the spectral characteristics of the plants were the most obvious; (4) Fisher linear discriminant analysis found that during fractional order to integer promotion, classification accuracy of the 0.8 order derivative was higher than the integer order derivatives. Therefore, the “trilateral” characteristics of plants spectra in the 0.8 order derivatives were more accurate than the first derivative. The 0.8 order derivative was more advantageous to distinguishing plants, with a classification accuracy of 89.37%, indicating the potential of 0.8-order derivative for hyperspectral remote sensing of plants. This study introduced a fractional order derivative to hyperspectral remote sensing for the quantitative analysis of differences in the vegetation spectrum, provided new insights to the research and application of vegetation remote sensing.     

Establishment of Restoration Trajectories for Upland Tundra Communities on Diamond Mine Wastes in the Canadian Arctic

Mining in the arctic amplifies restoration challenges due to inherent environmental conditions by removing soil, vegetation, and the propagule bank, adding coarse textured wastes with low water holding capacity and nutrients, and introducing salt and metal contamination. Short‐term reclamation focuses on rebuilding soil and providing rapid native plant cover for erosion control, supporting longer term reestablishment of ecological processes for sustainable tundra communities that provide essential wildlife habitat. This study evaluated methods to restore soil and plant communities 5 years after implementation of treatments at a diamond mine in the Canadian arctic. Five substrates including mine waste materials (processed kimberlite, glacial till, gravel, and mixes), four amendments (inorganic fertilizer, salvaged soil, sewage sludge, and water treatment sludge), five native species seed mixes and natural recovery were investigated. Soil and plant response were assessed annually. Soil chemistry was ameliorated with time. Chromium, cobalt, and nickel concentrations in processed kimberlite remained high and potentially toxic to plants. Adding fine textured materials such as glacial till to mine wastes improved nutrient and water retention, which in turn enhanced revegetation. Sewage and inorganic fertilizer increased available nitrogen and phosphorus, plant density and cover. Soil amendment increased species richness. Seeding was essential to establish a vegetation cover. After 5 years, seed mix composition and diversity had no effect on plant community development; soil and plant community properties among treatments changed considerably, providing evidence that restoration in the arctic is dynamic yet slow and success cannot be determined in the short term.     

Geochemical baseline establishment and ecological risk evaluation of heavy metals in greenhouse soils from Dongtai,China

Currently, heavy metal (HM) contamination in greenhouse soils is a significant concern due to the rapid expansion of greenhouse agriculture. However, it is difficult to accurately assess HM pollution in greenhouse soils in China due to the lack of local geochemical baseline concentrations (GBCs) or corresponding background values. In the present study, the GBCs of HMs in Dongtai, a representative greenhouse area of China, were established from subsoils using cumulative frequency distribution (CFD) curves. The pollution levels of HMs and potential ecological risks were investigated using different quantitative indices, such as geo-accumulation index (I_geo), pollution index (PI), pollution load index (PLI) and ecological risk index (RI), based on these regional GBCs. The total concentrations of six metals (Cd, Cr, Cu, Ni, Pb and Zn) in surface soils were determined and shown to be lower than the concentrations reported in other greenhouse regions of China. The GBCs of Cd, Cr, Cu, Ni, Pb and Zn were 0.059–0.092, 39.20–54.50, 12.52–15.57, 20.63–23.26, 13.43–16.62 and 43.02–52.65 mg kg⁻¹, respectively. Based on this baseline criterion, Cd, Pb and Zn accumulated in the surface soils because they were present at concentrations higher than their baseline values. The soils were moderately polluted by Cd according to the I_geo values, and the PI results indicated that moderate Cd contamination was present in this area. The large variation of I_geo value of Cd revealed that Cd in this area was likely influenced by agricultural activities. The PLI showed that most of the study area was moderately polluted. However, an analysis of the RI showed that the investigated HMs had low ecological risks. Correlation analysis and principle component analysis suggested that the Cd, Pb and Zn in the greenhouse soils mainly originated from anthropogenic sources (agricultural activities, atmospheric deposition etc.), while Cr, Cu, and Ni originated from natural sources. The findings of this study illustrated the necessity of GBC establishment at the local scale to facilitate more accurate HM evaluation of greenhouse soils. It is advisable to pay more attention to Cd, which could cause environmental problems in the greenhouse system.     

Mitigation of Heavy Metal Contamination in Soil via Successive Pig Slurry Application

This study evaluates heavy metal removal associated with phytomass management in a Typic Hapludox after three applications of pig slurry. Like humic acids in pig slurry were characterized through physics and chemical spectroscopy technics. Heavy metal levels were determined in ration that was offered to pigs, anaerobically digested pig slurry, and plant tissues from pig slurry-fertilized black oat (Avena strigosa Schreb.) and ryegrass (Lolium multiflorum Lam.) intercrop. Soil contamination was evaluated by the pseudo-total heavy metal levels in six soil layers and the bioavailable levels in the top soil layer. Results indicate that the ration is the origin of heavy metals in the pig slurry. The approximate levels in the ration were as follows (mg kg^?1): Cu 23.9, Zn 92.02, 153.15, Mn 30.98, Ni 0.23, Pb 10.75, Cr 0.34, Co 0.08, and Cd 0.05. The approximate levels of these metals in the pig slurry were as follows (mg kg^?1): Cu 71.08, Zn 345.67, Fe 83.02, Mn 81.71, Ni 1.13, Pb 4.35, Co 0.28, and Cd 0.16. Like humic acids contained 55% aliphatic chains, 14% oxygenated aliphatic chains, and 15% carboxyls, demonstrating their high capacity for interaction with heavy metals by forming soluble complexes. Soil contamination was indicated by the accumulation of heavy metals in the six soil layers in relation to the applied pig slurry dose (ranged as follows (mg kg^?1): Cu 110 to 150, Zn 50 to 120, Ni 20 to 40, and Pb 12 to 16) and as bioavailable forms (levels ranged as follows (mg kg^?1): Cu < 1, Zn 1.0–1.5, Ni 0.1–1.5, and Pb 1.9–6.3). The positive correlation between heavy metal accumulation in the plants and soil bioavailable heavy metal levels and the lowest heavy metal levels under higher intensity of phytomass removal demonstrate the ability of phytomass management to reduce soil contamination.     

Translocation of Herb-Rich Grassland from a Site in Wales Prior to Opencast Coal Extraction

Reinstatement of vegetation to a similar condition to that prior to disturbance is often required in industrial restoration schemes. Seeding with specially prepared seed mixes containing species suited to local soils is often the preferred option on grounds of practicality and cost. Turf translocation is more difficult and costly but, if successful, meets the reinstatement requirement more precisely. In a pilot study at a proposed opencast coal site in Wales, we compared the effectiveness of whole-turf translocation of herb-rich mesic grassland communities, with a less technically demanding and more cost-effective technique involving spreading turf over twice the area at the receiver site and rotovating it into the underlying soil. The translocated whole turf and rotovated turf plots were cut annually and the vegetation removed to simulate grazing that had occurred prior to translocation. Both the whole-turf and rotovated turf transplant techniques gave successful re-establishment of 50% or more of the species originally present. After three years, the cover and species composition were similar in “whole-turf” and “spread and rotovated” plots. This suggests that the “spread and rotovate” technique provides a satisfactory ecological alternative to whole-turf translocation. However, plant communities changed, in some cases substantially, after translocation using either technique. Altered soil hydrology and nutrition combined with the substitution of cutting for grazing are probably the main causes of these changes.     

Evaluating “Hot Spots” of Soil Contamination (Redux)

Every day, thousands of soil samples are collected from properties suspected of being contaminated. The samples are sent to laboratories where the chemical constituents are quantified. Frequently, one or more samples are identified as constituting a “hot spot” of soil contamination. The consequences of such a determination—more sampling, more remediation, more reporting—are often quite expensive. Yet despite the often costly consequences of identifying a “hot spot,” there appears no supportable methodology for objectively deciding which spots are “hot” and which are “not.” This can lead to situations where sampling episodes are required to demonstrate that there is not a problem, even though just exactly what would comprise a “problem” is not particularly clear and sometimes is not stated. The authors provide a review and analysis of common and published information concerning “hot spots.” They then present a different point of view about “hot spots” from those in common practice, a point of view that will challenge many environmental professionals to reconsider how they evaluate sampling results.     

Nutrient supply in undrained and drained Calthion meadows

Abstract. Plant species-rich Calthion meadows on mesotrophic fen peat soil extensively cut for hay are among the endangered semi-natural vegetation types in northwestern Europe. They are often badly affected by lowering the groundwater table (drainage) and fertilization. In a comparative study of an undrained site with a Calthion meadow and an adjacent drained site, availability of N, P and K was biologically assessed under field conditions (for two years) as well as in a greenhouse (for 18 weeks) by measuring shoot responsiveness. Also, experimental wetting of intact turf samples taken from both sites was applied in order to study the interaction between nutrient supply and anaerobic soil conditions. It was concluded that the above-ground phytomass yield in the undrained site was restricted by a major shortage of N-supply and a moderate shortage of K-supply by the fen peat soil. The above-ground phytomass yield of the drained site was only reduced by a strongly limited supply of K by the soil. The extent of K-deficiency was larger for the drained site. No P-deficiency was observed in any of the drained or undrained sites. Rewetting turf samples, taken from the drained site, did not change above-ground phytomass yields, suggesting that nutrient supplies were not affected by rewetting. Leaching has likely resulted in a strong reduction of K-supply in the drained site. It is assumed that a shortage in K-supply from the peat soil may have become an important environmental constraint for characteristic plant species of Calthion meadows. This may hamper the development of this meadow type on drained peat soils after rewetting by groundwater discharge.