Potential Phytoextraction and Phytostabilization of Perennial Peanut on Copper-Contaminated Vineyard Soils and Copper Mining Waste

This study sought to evaluate the potential of perennial peanut (Arachis pintoi) for copper phytoremediation in vineyard soils (Inceptisol and Mollisol) contaminated with copper and copper mining waste. Our results showed high phytomass production of perennial peanut in both vineyard soils. Macronutrient uptakes were not negatively affected by perennial peanut cultivated in all contaminated soils. Plants cultivated in Mollisol showed high copper concentrations in the roots and shoots of 475 and 52 mg kg⁻¹, respectively. Perennial peanut plants showed low translocation factor values for Cu, although these plants showed high bioaccumulation factor (BCF) for both vineyard soils, Inceptisol and Mollisol, with BCF values of 3.83 and 3.24, respectively, being characterized as a copper hyperaccumulator plant in these soils. Copper phytoextraction from Inceptisol soil was the highest for both roots and entire plant biomass, with more than 800 mg kg⁻¹ of copper in whole plant. The highest potential copper phytoextraction by perennial peanut was in Inceptisol soil with copper removal of 2,500 g ha⁻¹. Also, perennial peanut showed high potential for copper phytoremoval in copper mining waste and Mollisol with 1,700 and 1,500 g of copper per hectare, respectively. In addition, perennial peanuts characterized high potential for phytoextraction and phytostabilization of copper in vineyard soils and copper mining waste.     

Low Concentration of Copper Inhibits Colonization of Soil by the Arbuscular Mycorrhizal Fungus <Emphasis Type="Italic">Glomus intraradices</Emphasis> and Changes the Microbial Community Structure

Common agricultural practices result in accumulation of copper in agricultural soils worldwide. The effect of bioavailable copper ([Cu]_bio) on colonization of soil by the AM fungus Glomus intraradices and other soil microorganisms was investigated in microcosms containing copper-amended soil. To avoid indirect effects through the plant, copper was only added to root-free microcosm compartments. [Cu]_bio was measured using a Pseudomonas fluorescens biosensor strain. In the range of 0–1.5 μg g⁻¹ [Cu]_bio, a log–log linear relationship between added copper and [Cu]_bio was found. Microbial colonization of the root-free compartment was evaluated by whole-cell fatty acid analysis (WCFA) and amplified rDNA restriction analysis (ARDRA). The WCFA analysis showed that the AM fungus soil colonization was severely inhibited by Cu with a 50% reduction of mycorrhizal growth at 0.26 μg g⁻¹ [Cu]_bio. The growth of other main microbial groups was not significantly affected by copper. However, ARDRA analysis showed a very strong effect of copper on the bacterial community composition probably caused by an increased proportion of Cu-resistant bacteria. Our results suggest that problems with plant yield may arise when converting slightly copper-contaminated soils to land uses such as low-input and sustainable agriculture that are dependent on AM fungal symbiosis.     

Copper uptake and phytotoxicity as assessed in situ for durum wheat (Triticum turgidum durum L.) cultivated in Cu-contaminated, former vineyard soils

This work assessed in situ, copper (Cu) uptake and phytotoxicity for durum wheat (Triticum turgidum durum L.) cropped in a range of Cu-contaminated, former vineyard soils (pH 4.2–7.8 and total Cu concentration 32–1,030 mg Cu kg⁻¹) and identified the underlying soil chemical properties and related root-induced chemical changes in the rhizosphere. Copper concentrations in plants were significantly and positively correlated to soil Cu concentration (total and EDTA). In addition, Cu concentration in roots which was positively correlated to soil pH tended to be larger in calcareous soils than in non-calcareous soils. Symptoms of Cu phytotoxicity (interveinal chlorosis) were observed in some calcareous soils. Iron (Fe)–Cu antagonism was found in calcareous soils. Rhizosphere alkalisation in the most acidic soils was related to decreased CaCl₂-extractable Cu. Conversely, water-extractable Cu increased in the rhizosphere of both non-calcareous and calcareous soils. This work suggests that plant Cu uptake and risks of Cu phytotoxicity in situ might be greater in calcareous soils due to interaction with Fe nutrition. Larger water extractability of Cu in the rhizosphere might relate to greater Cu uptake in plants exhibiting Cu phytotoxic symptoms.     

The reserve of weatherable primary silicates impacts the accumulation of biogenic silicon in volcanic ash soils

Banana plantlets (Musa acuminata cv Grande Naine) cultivated in hydroponics take up silicon proportionally to the concentration of Si in the nutrient solution (0–1.66 mM Si). Here we study the Si status of banana plantlets grown under controlled greenhouse conditions on five soils developed from andesitic volcanic ash, but differing in weathering stage. The mineralogical composition of soils was inferred from X-ray diffraction, elemental analysis and selective chemical/mineralogical extractions. With increasing weathering, the content of weatherable primary minerals decreased. Conversely, clay content increased and stable secondary minerals were increasingly dominant: gibbsite, Fe oxides, allophane, halloysite and kaolinite. The contents of biogenic Si in plant and soil were governed by the reserve of weatherable primary minerals. The largest concentrations of biogenic Si in plant (6.9–7 g kg⁻¹) and soil (50–58 g kg⁻¹) occurred in the least weathered soils, where total Si content was above 225 g kg⁻¹. The lowest contents of biogenic Si in plant (2.8–4.3 g kg⁻¹) and soil (8–31 g kg⁻¹) occurred in the most weathered desilicated soils enriched with secondary oxides and clay minerals. Our data imply that soil weathering stage directly impacted the soil-to-plant transfer of silicon, and thereby the stock of biogenic Si in a soil–plant system involving a Si-accumulating plant. They further imply that soil type can influence the silicon soil–plant cycle and its hydrological output.     

Microbial Diversity and Community Structure in Two Different Agricultural Soil Communities

Abstract In this study, two different agricultural soils were investigated: one organic soil and one sandy soil, from Stend (south of Bergen), Norway. The sandy soil was a field frequently tilled and subjected to crop rotations. The organic soil was permanent grazing land, infrequently tilled. Our objective was to compare the diversity of the cultivable bacteria with the diversity of the total bacterial population in soil. About 200 bacteria, randomly isolated by standard procedures, were investigated. The diversity of the cultivable bacteria was described at phenotypic, phylogenetic, and genetic levels by applying phenotypical testing (Biolog) and molecular methods, such as amplified rDNA restriction analysis (ARDRA); hybridization to oligonucleotide probes; and REP-PCR. The total bacterial diversity was determined by reassociation analysis of DNA isolated from the bacterial fraction of environmental samples, combined with ARDRA and DGGE analysis. The relationship between the diversity of cultivated bacteria and the total bacteria was elucidated. Organic soil exhibited a higher diversity for all analyses performed than the sandy soil. Analysis of cultivable bacteria resulted in different resolution levels and revealed a high biodiversity within the population of cultured isolates. The difference between the two agricultural soils was significantly higher when the total bacterial population was analyzed than when the cultivable population was. Thus, analysis of microbial diversity must ultimately embrace the entire microbial community DNA, rather than DNA from cultivable bacteria.     

Revisiting copper and cobalt concentrations in supposed hyperaccumulators from SC Africa: influence of washing and metal concentrations in soil

Metal concentrations have been determined in shoots of 12 species considered as Cu and/or Co hyperaccumulators, collected from five subpopulations in a Cu/Co mine in Katanga. Samples have been subjected to three cleansing protocols (water, alconox, alconox + EDTA). Cu/Co concentrations were significantly higher when demineralised water was used to wash samples compared to more aggressive solutions. Washing effect was largest for species with velvety (Acalypha cupricola) or sticky (Haumaniastrum katangense) indumentum. Element concentrations in shoots varied by two orders of magnitude, i.e. 45–2,891 mg kg⁻¹ Cu (median: 329 mg kg⁻¹) and 21–1,971 mg kg⁻¹ Co (median: 426 mg kg⁻¹) and were generally lower than previously published values. Only 9.3% of data exceeded the hyperaccumulation threshold (1,000 mg kg⁻¹) for Cu and 13% for Co. Shoot concentrations varied by up to two orders of magnitude among subpopulations within species which was partly explained by variation of metal concentrations in the soil. Although the species considered in this paper undisputedly accumulate Co and Cu up to very high concentrations that require specific shoot tolerance mechanisms, the concept of hyperaccumulation, as defined for other metals like Zn and Ni, needs to be critically re-examined for Cu and Co. Our results suggest that many species so far regarded as Co/Cu hyperaccumulators might eventually turn out to be indicators.     

Uptake by corn and chemical extractability of heavy metals from a four year compost treated soil

This paper gives the results from four-year field experiments on compost application, added at the maximum rate allowed by Italian legislation (30 t/ha/y). The purpose of the experiment was to evaluate any eventual heavy metal accumulation in soil and corn plants. Cadmium in corn plants increased particularly in the roots from 0.22 mg kg⁻¹ to 1.31 mg kg⁻¹, concentration of Zn and Cu increased in grains, from 26.8 to 35.8 and from 2.4 to 4.2 mg kg⁻¹ respectively. Relevant increase in the roots was detected for Zn from 34.6 to 146.8 mg kg⁻¹. Only in the 4th year Ni concentration increases in the root portion while the content of Pb and Cr in corn was generally unaffected by the compost application. Heavy metals in the soil determined by a sequential chemical extraction, indicated that extractability changed with time. A certain increase was found from the beginning to the end of the experiment particularly for Zn, from 23.3 mg kg⁻¹ to 45.1 mg kg⁻¹ in extractable forms. Nevertheless the extractable amounts are rather small in respect to the total heavy metal content of compost.     

Laccase Gene Composition and Relative Abundance in Oak Forest Soil is not Affected by Short-Term Nitrogen Fertilization

Anthropogenic nitrogen (N) deposition affects a wide range of soil processes including phenol oxidase (PO) activity and soil organic matter dynamics. Depression of phenol oxidase activity in response to N saturation is believed to be mediated by the activity of white-rot basidiomycetes, whose production of extracellular oxidative enzymes can be limited by high N availability. We examined the effect of short-term N deposition on basidiomycete laccase gene diversity and relative abundance in temperate oak forest soil in which significant decreases in phenol oxidase and increased SOM have been recorded in response to experimental N deposition. UniFrac was used to compare the composition of laccase genes between three control- and three nitrogen-fertilized (80 kg⁻¹ ha⁻¹ per year) oak forest soils. The relative abundance of laccase genes was determined from qPCR analysis of laccase and basidiomycete ITS gene abundances. Our results indicate that there was no significant shift in the composition of laccase genes between control- and N-fertilized soils, nor was there a significant change in the relative abundance of laccase genes. These data suggest that N deposition effects on mineral soil PO activity do not result from changes in laccase gene diversity of white-rot basidiomycetes but are likely the result of altered microbial abundance or expression in this ecosystem type. Furthermore, laccase gene composition may be tied to factors that structure microbial communities in general, as soil laccase gene communities are more similar to other forest soils than with the corresponding litter.     

Evaluating the effects of gross nitrogen mineralization,immobilization, and nitrification on nitrogen fertilizer availability in soil experimentally contaminated with diesel

Sandy clay loam soil was contaminated with 5000 mg kg⁻¹ diesel, and amended with nitrogen (15.98 atom% ¹⁵N) at 0, 250, 500, and 1000 mg kg⁻¹ to determine gross rates of nitrogen transformations during diesel biodegradation at varying soil water potentials. The observed water potential values were −0.20, −0.47, −0.85, and −1.50 MPa in the 0, 250, 500, and 1000 mg kg⁻¹ nitrogen treatments respectively. Highest microbial respiration occurred in the lowest nitrogen treatment suggesting an inhibitory osmotic effect from higher rates of nitrogen application. Microbial respiration rates of 185, 169, 131, and 116 mg O₂ kg⁻¹ soil day⁻¹ were observed in the 250, 500, control and 1000 mg kg⁻¹ nitrogen treatments, respectively. Gross nitrification was inversely related to water potential with rates of 0.2, 0.04, and 0.004 mg N kg⁻¹ soil day⁻¹ in the 250, 500, and 1000 mg kg⁻¹ nitrogen treatments, respectively. Reduction in water potential did not inhibit gross nitrogen immobilization or mineralization, with respective immobilization rates of 2.2, 1.8, and 1.8 mg N kg⁻¹ soil day⁻¹, and mineralization rates of 0.5, 0.3, and 0.3 mg N kg⁻¹ soil day⁻¹ in the 1000, 500, and 250 mg kg⁻¹ nitrogen treatments, respectively. Based on nitrogen transformation rates, the duration of fertilizer contribution to the inorganic nitrogen pool was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg kg⁻¹ nitrogen treatments, respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and nitrification were considered losses of fertilizer with only gross mineralization of organic nitrogen contributing to the most active portion of the nitrogen pool.     

Rice grain zinc concentrations as affected by genotype, native soil-zinc availability, and zinc fertilization

The development of rice (Oryza sativa L.) cultivars with a higher Zn content in their grains has been suggested as a way to alleviate Zn malnutrition in human populations subsisting on rice in their daily diets. This study was conducted to evaluate the effects of native soil Zn status and fertilizer application on Zn concentrations in grains of five rice genotypes that had previously been identified as either high or low in grain Zn. Genotypes were grown in field trials at four sites ranging in native soil-Zn status from severely deficient to high in plant available Zn. At each site a −Zn plot was compared to a +Zn plot fertilized with 15 kg Zn ha⁻¹. Results showed that native soil Zn status was the dominant factor to determine grain Zn concentrations followed by genotype and fertilizer. Depending on soil-Zn status, grain Zn concentrations could range from 8 mg kg⁻¹ to 47 mg kg⁻¹ in a single genotype. This strong location effect will need to be considered in estimating potential benefits of Zn biofortification. Our data furthermore showed that it was not possible to simply compensate for low soil Zn availability by fertilizer applications. In all soils fertilizer Zn was taken up as seen by a 50–200% increase in total plant Zn content. However, in more Zn deficient soils this additional Zn supply improved straw and grain yield and increased straw Zn concentrations by 43–95% but grain Zn concentrations remained largely unchanged with a maximum increase of 6%. Even in soils with high Zn status fertilizer Zn was predominantly stored in vegetative tissue. Genotypic differences in grain Zn concentrations were significant in all but the severely Zn deficient soil, with genotypic means ranging from 11 to 24 mg kg⁻¹ in a Zn deficient soil and from 34 to 46 mg kg⁻¹ in a high Zn upland soil. Rankings of genotypes remained largely unchanged from Zn deficient to high Zn soils, which suggests that developing high Zn cultivars through conventional breeding is feasible for a range of environments. However, it may be a challenge to develop cultivars that respond to Zn fertilizer with higher grain yield and higher grain Zn concentrations when grown in soils with low native Zn status.     

Soluble Organic Nitrogen Pools in Forest soils of Subtropical Australia

Soil soluble organic N (SON) plays an important role in N biogeochemical cycling. In this study, 22 surface forest soils (0–10 cm) were collected from southeast Queensland, Australia, to investigate the size of SON pools extracted by water and salt solutions. Approximately 5–45 mg SON kg⁻¹, 2–42 mg SON kg⁻¹ and 1–24 SON mg kg⁻¹ were extracted by 2 M KCl, 0.5 M K₂SO₄ and water, on average, corresponding to about 21.1, 13.5 and 7.0 kg SON ha⁻¹ at the 0–10 cm forest soils, respectively. These SON pools, on average, accounted for 39% (KCl extracts), 42% (K₂SO₄ extracts) and 43% (water extracts) of total soluble N (TSN), and 2.3% (KCl extracts), 1.3% (K₂SO₄ extracts) and 0.7% (water extracts) of soil total N, respectively. Large variation in SON pools observed across the sites in the present study may be attributed to a combination of factors including soil types, tree species, management practices and environmental conditions. Significant relationships were observed among the SON pools extracted by water, KCl and K₂SO₄ and microbial biomass N (MBN). In general, KCl and K₂SO₄ extracted more SON than water from the forest soils, while KCl extracted more SON than K₂SO₄. The SON and soluble organic C (SOC) in KCl, K₂SO₄ and water extracts were all positively related to soil organic C, total N and clay contents. This indicates that clay and soil organic matter play a key role in the retention of SON in soil.     

Gaps and Soil C Dynamics in Old Growth Northern Hardwood–Hemlock Forests

Old growth forest soils are large C reservoirs, but the impacts of tree-fall gaps on soil C in these forests are not well understood. The effects of forest gaps on soil C dynamics in old growth northern hardwood–hemlock forests in the upper Great Lakes region, USA, were assessed from measurements of litter and soil C stocks, surface C efflux, and soil microbial indices over two consecutive growing seasons. Forest floor C was significantly less in gaps (19.0 Mg C ha⁻¹) compared to gap-edges (39.5 Mg C ha⁻¹) and the closed forest (38.0 Mg C ha⁻¹). Labile soil C (coarse particulate organic matter, cPOM) was significantly less in gaps and edges (11.1 and 11.2 Mg C ha⁻¹) compared to forest plots (15.3 Mg C ha⁻¹). In situ surface C efflux was significantly greater in gaps (12.0 Mg C ha⁻¹ y⁻¹) compared to edges and the closed forest (9.2 and 8.9 Mg C ha⁻¹ y⁻¹). Microbial biomass N (MBN) was significantly greater in edges (0.14 Mg N ha⁻¹) than in the contiguous forest (0.09 Mg N ha⁻¹). The metabolic quotient (qCO₂) was significantly greater in the forest (0.0031 mg CO₂ h⁻¹ g⁻¹/mg MBC g⁻¹) relative to gaps or edges (0.0014 mg CO₂ h⁻¹ g⁻¹/mg MBC g⁻¹). A case is made for gaps as alleviators of old growth forest soil C saturation. Relative to the undisturbed closed forest, gaps have significantly less labile C, significantly greater in situ surface C efflux, and significantly lower decreased qCO₂ values.     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana     

Soil-mixing effects on inorganic nitrogen production and consumption in forest and shrubland soils

Soils that are physically disturbed are often reported to show net nitrification and NO₃⁻ loss. To investigate the response of soil N cycling rates to soil mixing, we assayed gross rates of mineralization, nitrification, NH₄⁺ consumption, and NO₃⁻ consumption in a suite of soils from eleven woody plant communities in Oregon, New Mexico, and Utah. Results suggest that the common response of net NO₃⁻ flux from disturbed soils is not a straightforward response of increased gross nitrification, but instead may be due to the balance of several factors. While mineralization and NH₄⁺ assimilation were higher in mixed than intact cores, NO₃⁻ consumption declined. Mean net nitrification was 0.12 mg N kg⁻¹ d⁻¹ in disturbed cores, which was significantly higher than in intact cores (−0.19 mg N kg⁻¹ d⁻¹). However, higher net nitrification rates in disturbed soils were due to the suppression of NO₃⁻ consumption, rather than an increase in nitrification. Our results suggest that at least in the short term, disturbance may significantly increase NO₃⁻ flux at the ecosystem level, and that N cycling rates measured in core studies employing mixed soils may not be representative of rates in undisturbed soils.     

Chemistry of Cr in some Swedish soils

The effect of Si(OH)₄ on Cr toxicity and elemental concentrations in ryegrass were investigated in a growth chamber using an acid and a neutral mineral soil. Each soil was treated with 50 mg Cr, as CrO₃, kg⁻¹ soil dry weight, singly, or in combination with 25 mg Si as Si(OH)₄. Plants growing in unamended soils were used as controls. Chromium toxicity, expressed as decrease in shoot or root dry weight, was increased by the Si. This increase was accompanied by a higher Cr uptake particularly on the acid soil. The shoot and root dry weights were significantly correlated (P=1%) with the concentration of Cr, where r=−0.80 and −0.65, respectively. Uptake of Al, Cu, Fe, P and Zn did not show any consistent relationship to the magnitude of Cr toxicity.     

Functional Diversity of Culturable Bacterial Communities in the Rhizosphere in Relation to Fine-root and Soil Parameters in Alder Stands on Forest, Abandoned Agricultural, and Oil-shale Mining Areas

Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing the functional diversity and activity of microbial communities in the soil–root interface and in the bulk soil in relation to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine community-level physiological profiles (CLPP) of culturable bacteria in soil–root interface and bulk soil samples. CLPP were summarized as AWCD (average well color development, OD 48 h⁻¹) and by Shannon diversity index, which varied between 4.3 and 4.6 for soil–root interface. The soil–root interface/bulk soil ratio of AWCD was estimated. Substrate-induced respiration (SIR) and basal respiration (BAS) of bulk soil samples were measured and metabolic quotient (Q = BAS/SIR) was calculated. SIR and Q varied from 0.24 to 2.89 mg C g⁻¹ and from 0.12 to 0.51, respectively. Short-root morphological studies were carried out by WinRHIZO^TM Pro 2003b; mean specific root area (SRA) varied for grey alder and black alder from 69 to 103 and from 54 to 155 m² kg⁻¹, respectively. The greatest differences between AWCD values of culturable bacterial communities in soil–root interface and bulk soil were found for the young alder stands on oil-shale mining spoil and on abandoned agricultural land. Soil–root interface/bulk soil AWCD ratio, ratio for Shannon diversity indices, and SRA were positively correlated. Foliar assimilation efficiency (FOE) was negatively correlated with soil–root interface/bulk soil AWCD ratio. The impact of soil and alder species on short-root morphology was significant; short-root tip volume and mass were greater for black alder than grey alder. For the investigated microbiological characteristics, no alder-species-related differences were revealed.     

Composition of organic matter in sandy relict and cultivated heathlands as examined by pyrolysis-field ionization MS

Unusually high SOC levels have been reported for sandy cropland soils in North-Western Europe. A potential link with their general heathland land-use history was investigated by comparing two soil pairs of relict heathland and cultivated former heathland in the Belgian sandy region. A sequential chemical fractionation yielded similar sizes in corresponding SOM fractions between the heathland and cropland soils (i.e. NaOCl resistant: 12.3–15.0 g C kg⁻¹ and NaOCl + HF resistant: 2.6–5.3 g C kg⁻¹). Higher amounts of clay sized N in the cropland plots can be attributed to N additions from mineral fertilizers and animal manure. Temperature resolved Pyrolysis Field Ionization Mass Spectroscopy analysis showed that the composition of both relict heathland and cultivated soils was surprisingly similar, in spite of over 60 years of intense cropland management. The mass spectra of SOM in both heathland-cropland soil pairs investigated was dominated by signals from lipids, alkylaromatics and sterols. The accumulation of this SOM rich in aliphatics was logically linked to the high input of lipids, long-chain aliphatics and sterols from heathland vegetation and the low soil pH and microbial activity. Based on the relatively high OC surface loadings of HF-extractable OM (13–44 mg C m⁻² Fe and 1.2–2.3 mg C m⁻² clay), direct organo-mineral bonds between OM and Fe-oxides or clay minerals seem to be only partly involved as a stabilization mechanism in these soils. The distinct bimodal shape of the thermograms indicates that OM-crosslinking could furthermore contribute substantially to SOM stabilization in these soils. This study therefore corroborates the previously proposed view that lipids may be bound in networks of alkylaromatics, the structural building blocks of OM macromolecules. We hypothesize that such binding is able to explain the measured retention of these OM components, even under several decades of cropland management.     

Decline of soil nitrogen mineralization and nitrification during forest conversion of evergreen broad-leaved forest to plantations in the subtropical area of Eastern China

We examined soil nitrogen (N) mineralization and nitrification rates, and soil and forest floor properties in one native forest: evergreen broad-leaved forest (EBLF), one secondary shrubs (SS), and three adjacent plantation forests: Chinese fir plantation (CFP), bamboo plantation (BP) and waxberry groves (WG) in Tiantong National Forest Park, Eastern China. All forests showed seasonal dynamics of N mineralization and nitrification rates. Soil N mineralization rate was highest in EBLF (1.6 ± 0.3 mg-N kg⁻¹ yr⁻¹) and lowest in CFP (0.4 ± 0.1 mg-N kg⁻¹ yr⁻¹). Soil nitrification rate was also highest in EBLF (0.6 ± 0.1 mg-N kg⁻¹ yr⁻¹), but lowest in SS (0.02 ± 0.01 mg-N kg⁻¹ yr⁻¹). During forest conversion of EBLF to SS, CFP, BP and WG, soil N mineralization rate (10.7%, 73%, 40.3% and 69.8%, respectively), soil nitrification rate (94.9%, 32.2%, 33.9% and 39%, respectively), and soil N concentration (50%, 65.4%, 78.9% and 51.9%, respectively) declined significantly. Annual soil N mineralization was positively correlated with total C and N concentrations of surface soil and total N concentration of forest floor, and negatively correlated with soil bulk density, soil pH and C:N ratio of forest floor across the five forests. Annual soil nitrification was positively correlated with total C concentration of surface soil and N concentration of forest floor, and negatively correlated with soil bulk density and forest floor mass. In contrast, annual soil nitrification was not correlated to pH value, total N concentration, C:N ratio of surface soil and total C concentration and C:N ratio of forest floor.     

Dependence between Cu concentration in the liver,kidneys and skeletal muscles of canine females

The aim of the investigations was the determination of the Cu contents in the liver, kidneys and skeletal muscles of canine females. Material for research was collected post mortem from 45 animals aged 1 to 18 years coming from the Warsaw area. The effect of the health state, age and life conditions on the distribution of copper in the investigated organs was estimated. That element was determined using the method of inductively coupled plasma-atomic emission spectrometry (ICP-AES). In the liver, the average Cu contents amounted to 24.04 mg kg⁻¹ wet weight, in kidneys to 2.90 mg kg⁻¹ wet weight and in muscles to 0.94 mg kg⁻¹ wet weight. The highest values of copper content in particular tissues and organs were noted in the group of animals with neoplastic changes. In respect to the animal age the highest mean values of the copper content were noted in the oldest animals. They amounted to 30.97 mg kg⁻¹ in the liver, 3.34 mg kg⁻¹ in kidneys and 1.18 mg kg⁻¹ wet weight in muscles. Considering life conditions of the dogs it was observed that the higher mean values in all the investigated organs occurred in dogs coming from the urban areas.     

The role of bacteria on heavy-metal extraction and uptake by plants growing on multi-metal-contaminated soils

Four bacterial isolates were examined for their ability to increase the availability of water soluble Cu, Cr, Pb and Zn in soils and for their effect on metals uptake by Zea mays and Sorghum bicolor. Random Amplified Polymorphic DNA (RAPD) analysis was used to show that the bacterial cultures were genetically diverse. Bacterial isolates S3, S28, S22 and S29 had 16S rRNA gene sequences that were most similar to Bacillus subtilis, Bacillus pumilus, Pseudomonas pseudoalcaligenes and Brevibacterium halotolerans based on 100% similarity in their 16S rDNA gene sequence, respectively. Filtrate liquid media that had supported B. pumilus and B. subtilis growth significantly increased Cr and Cu extraction from soil polluted with tannery effluent and from Cu-rich soil, respectively, compared to axenic media. The highest concentrations of Pb (0.2 g kg⁻¹), Zn (4 g kg⁻¹) and Cu (2 g kg⁻¹) were accumulated in shoots of Z. mays grown on Cu-rich soil inoculated with Br. halotolerans. The highest concentration of Cr (5 g kg⁻¹) was accumulated in S. bicolor roots grown in tannery-effluent-polluted soil inoculated with a mixed inoculum of bacterial strains. These results show that bacteria play an important role in increasing metal availability in soil, thus enhancing Cr, Pb, Zn and Cu accumulation by Z. mays and S. bicolor.