To establish this work, A. herba alba species were selected in the Algerian steppe region, and their soils were treated weekly with K2CrO4 solution for about three months. Chromium concentrations were determined in the soil and in the different plants’ parts to verify its absorption and translocation with and without pollution simulation.
This study demonstrated that A. herba alba has a strong resistance to high concentrations of hexavalent chromium. An increase in chromium concentrations at the different parts of plant’s has been noticed, without affecting its growth and vegetative development. The results of physiological and elementary analysis indicated that chromium was absorbed by A. herba alba. Cr (VI) accumulation in plant increase when they are increasing in soil. Translocation factor results indicated that Cr (VI) was mainly accumulated by A. herba alba roots. Particle size analysis showed that the soil is poor in organic substances and mostly sandy loams with 79.77% of sand and 9.76% of clay minerals. 相似文献
Nyssa sylvatica showed considerable Co accumulation; foliar Co concentration in the second harvest was as high as 800 mg/kg dry weight. The first few leaves that emerged were chlorotic, both in the Co-amended soil and Ni-contaminated soils, but with growth the signs of toxicity disappeared. In the Co amended soil, Co concentration in Nyssa sylvatica leaves was 30% of that found in shoots of Alyssum species, but an order of magnitude higher than that of Brassica juncea. The leaves accumulated a higher concentration compared with the stems.
Both Alyssum species and Nyssa sylvatica offer promise for phytoextraction of Co and 60Co from contaminated or mineralized soils. 相似文献
All the plants were effective in two years in the reclamation of the polluted soil, showing an average reduction of about 35%, 40%, and 70% in metals, TPH and PCB content, respectively. As regards the plants, the poplar contributed the most to organic removal. In fact, its ability to take up and detoxify organic pollutants is well known. Paulownia tomentosa, instead, showed high metal removal. The Cytisus scoparius was the least effective plant in soil decontamination. The recovery of soil functionality was followed by enzyme activities, expressing the biochemical processes underway, and nutrient content useful for plant growth and development. Throughout the area, an enhancement of metabolic processes and soil chemical quality was observed. All the enzymatic activities showed a general increase over time (until 3-4 fold than the initial value for urease and β-glucosidase). Moreover, Cytisus scoparius, even though it showed a lower decontamination capability, was the most effective in soil metabolic stimulation. 相似文献
The annual removal of the soil activity with the biomass was less than 0.1%. The addition of citric acid (25 mmol kg-1) 1 week before the harvest increased U uptake up to 500-fold. With a ryegrass and mustard yield of 15000 kg ha-1 and 10000 kg ha-1, respectively, up to 3.5% and 4.6% of the soil activity could annually be removed with the biomass.
With a desired activity reduction level of 1.5 and 5 for the bicarbonate washed and control soil, respectively, it would take 10 to 50 years to attain the release limit.
A linear relationship between the plant 238U concentration and the 238U concentration in the soil solution of the control, bicarbonate-washed, or citric acid-treated soil points to the importance of the soil solution activity concentration in determining U uptake and hence to the importance of solubilising agents to increase plant uptake.
However, citric acid addition resulted in a decreased dry weight production (all plants tested) and crop regrowth (in case of ryegrass). 相似文献
Aims: To determine differences in diversity patterns between serpentine and non-serpentine communities.
Methods: A two-year study was conducted in native eastern Mediterranean grasslands. For each year 40 0.25 m2 plots were sampled across four pairs of sites, each of which contained a serpentine and an adjacent non-serpentine plant community. Alpha and beta diversity (variation in species composition among plots within localities), species composition and biomass production were determined. Total soil elemental concentrations and pH were also measured.
Results: Serpentine habitats were shown to support a lower alpha diversity relative to non-serpentine habitatas on a per plot basis. Differences in alpha diversity between the two substrates were associated with variation in soil chemistry rather than above-ground biomass production. Serpentine habitats also exhibited lower beta diversity, which was unrelated to variation in biomass production. The two contrasting communities presented distinct species composition.
Conclusions: Differences in diversity patterns between serpentine and non-serpentine communities in the eastern Mediterranean are influenced by soil chemistry rather than biomass production. 相似文献
Aims: We used a highly invasive grass, Microstegium vimineum, as a model for understanding how changes in water-induced stress (including potential associated changes in soil nutrient availability) might affect mating systems and thus evolutionary change in invasive species. We predicted that plants would respond to increased water-induced stress through a relative reduction in investment in CL vs. CH reproduction (i.e., a decrease in the CL:CH ratio).
Methods: Under greenhouse conditions, we measured fecundity (number of inflorescences and florets per plant) as well as relative investment in CL vs. CH florets (CL:CH ratios for number of inflorescences, florets per inflorescence, overall florets) in response to three watering treatments approximating mesic (low) to inundated (high) conditions.
Results: Plant biomass was significantly lower in high-watering treatment relative to intermediate and low treatments, indicating that the high-water condition was stressful. Contrary to expectations, stressed plants significantly increased relative investment in CL reproduction, a pattern associated with decreased inflorescence number and increased numbers of CL florets per inflorescence.
Conclusions: We conclude that changes in water-induced stress could strongly influence realised rates of outcrossing in this invasive plant, leading to mating system evolution, and altered invasiveness. 相似文献
Aims: To assess the effects of different slope positions on soil properties and vegetation on a cut slope and to determine the key factor(s) affecting vegetation distribution on a cut slope in a semi-tropical environment.
Methods: Soil samples were collected in three slope positions: upper slope (US), middle slope (MS) and foot slope (FS). Soil pH, moisture and bulk density and concentrations of soil organic carbon (C), total nitrogen (NT), available nitrogen (NA), total phosphorus (PT), available phosphorus (PA), total potassium (KT) and available potassium (KA) were determined. Vegetation composition and cover were recorded along the slope. One-way analysis of variance (ANOVA), indicator species analysis (ISA) and detrended canonical correspondence analysis (DCCA) were applied to analyse differences in soil properties among slope positions and vegetation distributions.
Results: NT, NA, PT, PA, KA, C and pH tended to increase from the US to the FS. Two indicator species were abundant in their respective slope positions: Achyranthes bidentata in the FS and Dicranopteris dichotoma in the US. DCCA showed that pH and some soil nutrients (NA, PT, PA and C) influenced the vegetation distribution on cut slope.
Conclusions: Soil pH and some soil nutrients including NA, PT, PA and C had large impacts on vegetation distribution along slope positions in a semi-tropical area of China. We suggest increasing soil pH to provide a better soil environment for plant colonisation in further research concerning the restoration of such cut slopes. 相似文献
Methods: Limited (lSSc, n?=?76) and diffuse SSc (dSSc, n?=?41) fulfilling the ACR/EULAR 1980 and 2013 classification criteria for SSc and asymptomatic controls (n?=?9) were included. PRO-C1, PRO-C3 and PRO-C6 were measured in serum.
Results: LSSc compared to dSSc were significantly older, had longer disease duration and lower mRSS. PRO-C3 was higher in early dSSc compared to early lSSc (mean [95 percentile], 27.4 [13.1–39.1] ng/mL vs 14.9 [8.2–28.8] ng/mL, p?=?0.006). PRO-C6 levels were higher in early dSSc compared to early lSSc and late dSSc (early dSSc: 28.2 [10.4–92.3] ng/ml vs early lSSc: 11.0 [6.9–28.5] ng/ml; p?=?0.006 and late dSSc: 12.6 [6.5–25.3] ng/mL, p?=?0.04). No difference was observed with PRO-C1. PRO-C3 and PRO-C6 were moderately correlated with mRSS with R-partials of 0.36 (p?<?0.001) and 0.29 (p?=?0.002), respectively
Conclusion: Measures of type III and VI collagen formation are potential objective biomarkers of fibrosis in systemic sclerosis. These biomarkers could be useful in monitoring the disease and efficacy of treatment. 相似文献
Aims: The aim of this work was to investigate the effects of dispersal limitation and environmental filtering on tree recruitment. To accomplish this, we employed the unified neutral theory of biodiversity and biogeography to examine migration within the metacommunity, defined as a set of interacting local communities linked by the dispersal of multiple potentially interacting species.
Methods: We sampled 12,975 individuals with dbh ≥ 1 cm in 26 1-ha permanent plots, including habitats of terra firme, transitional forests, várzea and campinarana, on the upper Madeira River, Brazilian Amazon.
Results: Campinarana drew individuals from outside the metacommunity species pool at a mean probability of recruitment of 0.06, a much lower probability than terra firme (0.31), transitional (0.21) and várzea forests (0.22). Environmental variables, such as water table depth, soil texture and fertility, were related to differences in community assembly.
Conclusions: Species abundance distribution and diversity patterns of plant assemblages in a large river landscape in the Amazon highlight the importance of environmental heterogeneity that conditions beta-diversity. The high variation in recruitment probabilities from the metacommunity species pool to local communities suggests high habitat variability in the process of maintaining patterns of local diversity. 相似文献
Aims: We tested whether mesic deep-soil habitats on granite outcrops can sustain larger FD than dry shallow-soil habitats.
Methods: We calculated FD for dominant species for five single traits (leaf dry matter content, foliar δ13C, foliar C:N ratio, plant height and specific leaf area) and their combinations. We employed Generalized Additive Mixed Models to quantify the relationship between selected climate and soil depth variables, and FD.
Results: More benign (deep-soil) habitats supported larger FD for foliar C:N, plant height and for multiple traits than did shallow-soil habitats.
Conclusions: We suggest that: (1) functional diversification, likely aimed at avoiding intra- and interspecific competition for light and nutrients acquisition, might be the important factor in deep-soil habitats; (2) deep-soils patches on and around granite outcrops may serve as ecological microrefugia for biota associated with resource-rich environments. 相似文献
Aims: To determine how litter and standing vegetation affected seedling recruitment in plant communities in Tibetan alpine grasslands.
Methods: Seedling recruitment was quantified in response to experimental treatments: (1) removal of standing vegetation and litter; (2) removal of standing vegetation with litter intact; (3) intact standing vegetation and removal of litter and (4) control: intact standing vegetation and litter.
Results: Litter removal increased seedling numbers, while standing vegetation removal had no effect. An interaction between litter and standing vegetation removal marginally increased seedling number. Species richness of seedlings was not related to either litter removal or standing vegetation removal. Species composition of seedling differed significantly between removal of both litter and standing vegetation and control.
Conclusions: Litter and its interaction with standing vegetation has an important role in affecting plant species recruitment in this alpine plant community. In contrast, biotic interactions, such as competition or facilitation from standing vegetation, appear to have only minor effects on recruitment. 相似文献
Aims: To investigate effects of Eucalyptus saligna leaf litter on the colonisation and development of the ground layer by grassland species and if these effects were related to allelopathy.
Methods: We assessed the effects of Eucalyptus litter on the establishment of species of the native grassland community and on seeded test species (Paspalum notatum and Lotus corniculatus – introduced). We tested the impact of the addition of E. saligna leaf litter, artificial leaves (shading and mechanical impediment) and shading. We also tested the phytotoxicity of the soil from E. saligna plantations.
Results: Species richness, diversity, plant height, cover and biomass were lower in E. saligna leaves and artificial leaves treatments than in the control (absence of litter). The test species showed lower biomass and higher mortality in treatment plots with E. saligna leaves, artificial leaves and shading treatments than in the control. Allelochemicals did not accumulate in soil at phytotoxic levels.
Conclusions: Eucalyptus saligna leaf litter suppresses the establishment of grassland vegetation, but the effects are mainly physical. Field evaluations with appropriate controls should be more extensively used in allelopathy investigations. 相似文献
Aims: In order to assess the effects of large herbivores on above-ground vegetation (AGV) and soil seed bank (SSB) characteristics, intensively sheep-grazed areas were compared to adjacent areas where grazing had been removed 10 years previously in a sub-alpine grassland of northern Iran.
Methods: A total of 40 4-m2 (2 m × 2 m) plots were established in each treatment, and soil samples were collected from each plot within a depth of 10 cm. Plant species composition was determined for each plot during the flowering stage of herbaceous species in June 2011. The seedling emergence method was used to estimate SSB composition.
Results: A total of 45 species (23 annuals and 22 perennials) emerged from the soil samples of the grazed area, while the number of species emerged from the soil samples of the previously grazing area was 76 (37 annuals and 39 perennials). The removal of grazing led to a significant increase in species richness and seed density in the SSB. Species turnover of AGV was higher, and that of the SSB was similar for grazed areas compared with areas that were formerly grazed. Detrended correspondence analysis ordination of AGV composition showed a clearly separate structure between grazed plots and plots where grazing has been removed, while the segregation was less clear for SSB composition.
Conclusions: We concluded that restoration of locally degraded sites cannot rely on the SSB when grazing is stopped simultaneously and unvegetated gaps are colonised by vegetative growth rather than by seed. 相似文献
Aims: Here, we examine the relationship between productivity, functional group dominance and plant species richness at the plot scale in Tibetan Plateau meadows. These alpine meadows are ideal to examine the species productivity-richness relationship because they have a very high species richness, a large gradient in productivity, and can be dominated by either graminoids (grasses and sedges) or forbs.
Methods: We measured plant species richness and above-ground biomass along a natural gradient of functional group abundance in 44 plots distributed across five natural, winter-grazed but otherwise undisturbed sites in the eastern part of the Qing-Hai Tibetan Plateau, in Gansu province, China in 2008.
Results: Graminoid abundance (i.e. graminoid biomass as percent of the total above-ground biomass) explained 39% of plot differences in species richness while neither productivity nor the biomass of the three most abundant plant species, either individually or combined, were a significant predictor of species richness.
Conclusions: Our results show that within these alpine meadows, a shift from graminoid to forb dominance, rather than the individual dominant species or productivity itself, is strongly correlated with species richness. Thus, differences in functional group abundance can be a strong driver of observed plant species richness patterns. 相似文献