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Summary Recent droughts have strongly impacted forest ecosystems and are projected to increase in frequency, intensity, and duration in the future together with continued warming. While evidence suggests that tree diversity can regulate drought impacts in natural forests, few studies examine whether mixed tree plantations are more resistant to the impacts of severe droughts. Using natural variations in leaf carbon (C) and nitrogen (N) isotopic ratios, that is δ13C and δ15N, as proxies for drought response, we analyzed the effects of tree species richness on the functional responses of tree plantations to the pan‐European 2018 summer drought in seven European tree diversity experiments. We found that leaf δ13C decreased with increasing tree species richness, indicating less drought stress. This effect was not related to drought intensity, nor desiccation tolerance of the tree species. Leaf δ15N increased with drought intensity, indicating a shift toward more open N cycling as water availability diminishes. Additionally, drought intensity was observed to alter the influence of tree species richness on leaf δ15N from weakly negative under low drought intensity to weakly positive under high drought intensity. Overall, our findings suggest that dual leaf isotope analysis helps understand the interaction between drought, nutrients, and species richness. [ABSTRACT FROM AUTHOR]

Abstract Although biological soil crusts (BSCs) are known for a variety of ecological functions, the role of individual biocrust organism species in BSCs on their P cycling is almost unknown. To evaluate the hypothesis that the contribution of defined cultivable taxa of fungi and algea might influence the microbial P storage and mobilization in the underlying soil, a transect was investigated in a glacier foreland in the mountain plateau Hardangervidda in Southern Norway. Microbial biomass P storage in soil under BSC increased continuously with increasing distance to the glacier and increasing fungal species richness. Lowest soil phosphatase activity and soil organic matter content were linked with highest number of algal and fungal in the overlaying BSCs. Enhanced soil microbial biomass P was linked with an increasing water content and decreasing pH CaCl2 of the soil. Nine to 21 algal and 5 to 10 fungal taxa were identified per test site from BSCs along the transect. Members of the Eustigmatophyceae and Xanthophyceae were observed exclusively close to the glacier, those of Klebsormidiophyceae exclusively in larger distance. The most common fungal genera in the BSCs were Lecythophora , Penicillium, Rhizoscyphus and Pholiota, whereas Cosmospora sp., Thelebolus globosus and Mucor hiemalis were found exclusively close to the glacier. The presence of usually biomass-rich taxa in the soil crusts was related to an increased microbial P storage in total. An increasing impact of microbial P storage under BSCs on the subsequent successional vegetation development is suggested. Highlights • Microbial biomass P storage increased continuously with increasing distance to the glacier. • Microbial biomass P storage increased continuously with increasing fungal abundance. • Top-down control of fungi on P mobilization reflected by abundance of dark septate endophytes. [ABSTRACT FROM AUTHOR]

Early successional biological soil crusts (BSCs), a consortium of bacteria, cyanobacteria, and other microalgae, are one of the first settlement stages on temperate coastal sand dunes. In this study, we investigated the algal biomass (Chlorophyll a (Chl a)), algal (Calgal) and microbial carbon (Cmic), elemental stoichiometry (C:N:P), and acid and alkaline phosphatase activity (AcidPA and AlkPA) of two algae-dominated BSCs from a coastal white dune (northeast Germany, on the southwestern Baltic Sea) which differed in the exposure to wind forces. The dune sediment (DS) was generally low in total carbon (TC), nitrogen (TN), and phosphorus (TP). These elements, together with the soil organic matter (SOM) accumulated in the BSC layer and in the sediment underneath (crust sediment CS), leading to initial soil development. The more disturbed BSC (BSC1) exhibited lower algal and microbial biomass and lower Calgal/Cmic ratios than the undisturbed BSC (BSC2). The BSC1 accumulated more organic carbon (OC) than BSC2. However, the OC in the BSC2 was more effectively incorporated into Cmic than in the BSC1, as indicated by lower OC:Cmic ratios. The AcidPA (1.1-1.3 μmol g−1 DM h−1 or 147-178 μg g−1 DM h−1) and AlkPA (2.7-5.5 μmol g−1 DM h−1 or 372-764 μg g−1 DM h−1) were low in both BSCs. The PA, together with the elemental stoichiometry, indicated no P limitation of both BSCs but rather water limitation followed by N limitation for the algae community and a carbon limitation for the microbial community. Our results explain the observed distribution of early successional and more developed BSCs on the sand dune. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade, concerns about the future of its global supply have stimulated much research on soil P and method development. This review provides an overview of advanced state-of-the-art methods currently used in soil P research. These involve bulk and spatially resolved spectroscopic and spectrometric P speciation methods (1 and 2D NMR, IR, Raman, Q-TOF MS/MS, high resolution-MS, NanoSIMS, XRF, XPS, (µ)XAS) as well as methods for assessing soil P reactions (sorption isotherms, quantum-chemical modeling, microbial biomass P, enzymes activity, DGT, 33P isotopic exchange, 18O isotope ratios). Required experimental set-ups and the potentials and limitations of individual methods present a guide for the selection of most suitable methods or combinations. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi are an important component of the soil biota in most agroecosystems, and their association can directly or indirectly affect the diversity of soil microorganisms, nutrient cycling, and growth of host plants. Since not all crops are symbiotic, we hypothesized that the presence of AM fungi can: (1) inhibit the growth of non-host plants by resulting in biotic stress, or (2) promote their growth indirectly by increased nutrient mobilization. These hypotheses were tested in the present study on the non-mycorrhizal crop canola ( Brassica napus L.) in the presence and absence of other autochthonous soil microorganisms. The soil was inoculated with a mixture of AM fungi ( Acaulospora longula, Glomus geosporum, G. mosseae, Scutellospora calospora) and as a control, a non-inoculated soil was used. The impact of inoculation on plant growth (biomass production, nutrient concentrations) and expression of the stress protein metallothionein gene BnMT2 was investigated in the shoots. B. napus L. did not form mycorrhizal associations on its roots, but its growth was promoted after inoculation with AM fungi. In the soil with autochthonic microorganisms, growth inhibition after inoculation was observed compared to the control. The concentrations of N, P, K, and S in the shoot were always significantly increased after inoculation with AM fungi. However, this was partly combined with reduced growth and thereby decreased total uptake of nutrients. Expression of BnMT2 in the leaves was increased after inoculation with AM spores at the soil devoid of indigenous microorganisms, but decreased in their presence. The expression of stress proteins ( BnMT2) significantly increased with increasing length and biomass of shoots. In conclusion, the inhibition of the non-host plant B. napus L. following inoculation with AM fungi was confirmed, however, only in combination with autochthonous microorganisms. Growth promotion of B. napus L. in the presence of AM fungi in the absence of autochthonous soil microorganisms suggest that plant growth depression in the presence of AM fungi was based on interactive effects of AM fungi with the autochthonous microorganisms in the soil rather than on a direct impact of the AM fungi. [ABSTRACT FROM AUTHOR]

Although lipids are involved in diverse soil processes and affect various soil properties, the contribution of rhizodeposits and the root zone to lipid concentrations and distributions in soils is unknown. For the first time, we determined the concentrations of alkanoic acids, n-alkanes and n-alkenes in root zone leachates and roots of maize and potato using gas chromatography/mass spectrometry (GC/MS). In total, the lipid concentrations of leachates were 100 μg g−1 (maize) and 17 μg g−1 (potato). The saturated n-alkanoic acids, ranging from n-C14 to n-C28 and having the maximum at n-C22 (maize) and at n-C16 (potato), were more abundant than the other compounds. Maize leachates had more alkanes (20 μg g−1) than potato leachates (3.1 μg g−1), but the members of the homologues were nearly the same. Comparison of these distributions with data for roots, microorganisms and soil indicated that the lipids in the leachates from the root zone mainly originated from abrasion of fine roots, rhizodeposits and rhizosphere microorganisms. [ABSTRACT FROM PUBLISHER]

Nutrient leaching from dry (COD) and wet (COW) coffee, sisal (SIS), brewery barley malt (BEB) and sugar cane (FIC) by-products, and linseed (LIC) and niger seed cakes (NIC), and uptake by maize were studied in a pot experiment with tropical Alfisol. After three months, soils were leached to recover labile plant nutrients, and root and shoot biomass was harvested. The leachate from FIC-amended soil had the highest concentration of inorganic P (0.90 μmol L−1), whereas the highest concentrations of potassium (K) (48,088 μmol L−1) and calcium (2566 μmol L−1) were determined in leachates from COD and BEB treatments, respectively. The amendments significantly increased K uptake by maize proportional to the amount of K applied, but the effects for other plant nutrients were small. The results indicated that pre-decomposition of agro-industrial by-products may increase the nutrient release in tropical soils. [ABSTRACT FROM PUBLISHER]

The aim was to investigate how short rotation coppice (SRC) on arable soil in Northern Germany altered the concentrations of soil lipids, and thus, soil organic matter (SOM) quality. The concentrations of organic C and aliphatic lipids were determined in the litter and underlying soil layers under two willow ( Salix caprea × viminalis clone 6, S. viminalis clone 78-183) and two poplar ( Populus trichocarpa × deltoides cv. Beaupré, P. nigra × maximowiczii cv. Max 4) clones at a 14-year-old SRC and a permanent arable reference site. High organic C concentrations in the topsoil under S. viminalis and P. trichocarpa × deltoides agreed with high concentrations of long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes. These disproportionally higher concentrations of long C-chain saturated n-alkanoic acids (factor 3.6) and n-alkanols (factor 3.8) under S. viminalis and of n-alkanols (factor 3.9) under P. trichocarpa × deltoides than in an arable reference treatment indicated a lower microbial decomposability and, thus, a clone-specific accumulation of these SOM constituents. The clone-specific enrichments in long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes indicate that clone selection may be an approach to additional long-term storage of atmosphere CO in the form of stable SOM under SRC. [ABSTRACT FROM AUTHOR]

The majority of plants interacts with mycorrhizal fungi, which predominantly provide mutual benefits, but also costs. We tested the hypothesis that specific combinations of host plants (four commercial varieties of Salix spp.) and ectomycorrhizal partners (species of Laccaria, Paxillus, Tricholoma and Hebeloma) differ in their effects on the host foliar chemistry. Twenty specific host - mycorrhiza combinations were pot-grown outdoors under low-N conditions. Foliar concentrations of total phenolics and salicylic acid were decreased by mycorrhizas in S. schwerinii x S. viminalis and S. x dasyclados genotypes, but increased in S. viminalis. Mycorrhiza effects on host biomass production were positive, indifferent or negative, depending on the specific host—mycorrhiza combination. The host plant genotype influenced mainly the direction of mycorrhizal effects on foliar chemistry, whereas the magnitude of mycorrhizal effects varied mostly among the fungal genotypes. The results are relevant with respect to the possible interactions between mycorrhizas, plants and leaf herbivores. [ABSTRACT FROM AUTHOR]

Abstract: Low supply of the nutrients nitrogen (N) and phosphorus (P) limit plant growth and spreading, and increase the plant-microbial nutrient competition in subarctic and arctic regions. We investigated the mycorrhizal community structure of a polar shrub willow (Salix polaris) and the microbial turnover in its rhizosphere to explore the adaptation of a mycorrhizal plant in the subarctic tundra. The ectomycorrhizal colonisation ranged from 35 to 64% of the fine root tips and decreased with an increasing soil C/N ratio. In total, 16 ectomycorrhizal morphotypes were found under S. polaris (eight to 13 morphotypes per site, five morphotypes at all four sites). Cenococcum sp. was the most common EM fungus (32% of the ectomycorrhizal fine roots). The abundance of Cenococcum sp. increased with an increasing organic matter content and N/P ratio in the soil. Arbuscular mycorrhizal colonisation of S. polaris was absent or less than 1% of the fine root length. Microbial biomass P accounted for 21–75% of the organic soil P and 6–49% of the total soil P. Microbial biomass P, alkaline and acid phosphatase activities in the rhizosphere increased with increasing soil N concentration. We conclude that a higher N supply decreases the diversity in the mycorrhizal community on polar willows and increases the role of P turnover from the soil microbial biomass for the nutrient supply. [Copyright &y& Elsevier]

In order to enhance phytoremediation efficiency, we investigated the effects of dual inoculation with ectomycorrhizal fungi and the ectomycorrhiza associated bacteria Micrococcus luteus and Sphingomonas sp. on the growth and metal accumulation of willows (Salix viminalis x caprea) on contaminated soil. The bacterial strains were previously collected from sporocarps of ectomycorrhizal fungi. The bacteria increased plant growth and the mycorrhizal dependency of willows colonized with the ectomycorrhizal fungus Hebeloma crustuliniforme. The total cadmium (Cd) and zinc (Zn) accumulation in the shoot biomass was increased after inoculation with the fungal strain Hebeloma crustuliniforme in combination with Micrococcus luteus up to 53% and in combination with Sphingomonas sp. up to 62%, respectively. The dual inoculation in combination with Laccaria laccata did not increase the accumulation of Cd and Zn in the willows. We conclude that associated bacteria can enhance the ectomyorrhiza formation and growth of willows and, thereby, the Cd and Zn accumulation in the plant biomass. The results suggest that bacterial support of root growth promoting ectomycorrhizal fungi may be a promising approach to improve the remediation of metal-contaminated soils by using willows. [ABSTRACT FROM AUTHOR]

(1) Background: Weed control decreases the competition for nutrients, but also the potential of increased phosphorus (P) mobilization in soils caused by higher plant diversity. (2) Methods: Impacts of weed species under maize on mycorrhizal colonization and plant-availability of P were investigated in two pot experiments. Plant traits and P mobilization were tested in weed-free maize and in mixed growth with six annual weed species. (3) Results: Growth of maize decreased in treatments with weeds, while P concentrations in its shoots increased in mixed growth with C. album, E. crus-galli and P. convolvulus. Mycorrhizal colonization of maize without weeds was low (<20% of root length), but increased in mixed growth with C. album, E. crus-galli and V. arvensis up to 40%. The activities of Pmobilizing hydrolytic enzymes (phosphatases, ß-glucosidase) and plant-availability of P were occasionally higher under mixed growth with weeds. The dimension of weed impacts on P cycling under maize differed significantly between both experiments. (4) Conclusions: Weeds potentially promote P mobilization and mycorrhizal colonization under maize, but this impact is not guaranteed. The weed-based improved P supply of maize should be defined under field conditions to allow a controlled weed tolerance in maize cropping systems. [ABSTRACT FROM AUTHOR]

Crop residues such as straw are a favourable habitat of many pathogenic fungi in the soil. Therefore, the undesired accumulation of straw at the soil surface, which occurs regularly in conservation tillage systems, must be mitigated. The present study investigated the effects of an inoculation with the saprotrophic microfungus and potential biocontrol agent Trichoderma saturnisporum on the decomposition of wheat straw. The straw decomposition was investigated indirectly by an aerobic incubation experiment for 13 weeks, and directly by pyrolysis-field ionization mass spectrometry (Py-FIMS). Treatments comprised the addition of glucose, T. saturnisporum and T. saturnisporum with glucose. Soil respiration during the whole incubation period was significantly increased by inoculation with T. saturnisporum. The C/N ratio of the inoculated straw decreased strongly from an initial value of 76 to 43 after 4 weeks and to 30 after 13 weeks. Py-FIMS showed that inoculation with T. saturnisporum caused significant decreases in the sterol content of straw after 4 weeks. Thus, the results demonstrated the potential contribution of T. saturnisporum to accelerate wheat straw decomposition on soil. [ABSTRACT FROM AUTHOR]

The drilosphere is described as a microbial hotspot in soil, which is rich in labile nutrients. However, phosphorus (P) quality and availability change along the drilosphere from labile organically-bound P in upper layers to immobilized Ca-phosphate with increasing depth. In this study, we postulated (1) that microbial P turnover is generally accelerated in the drilosphere compared to bulk soil as a result of an increase in labile nutrients, and (2) that P mineralization is dominant in upper layers of the drilosphere and P solubilization in deeper layers of the drilosphere, respectively. Furthermore, we hypothesized (3) that the enhanced P mobilization in the drilosphere favors copiotrophic and earthworm gut derived bacteria like Pseudomonadaceae , which distinguishes the community composition from that of the bulk soil. We investigated the effect of earthworm activities on potential phosphatase activities, abundance and diversity of bacterial communities involved in P mobilization (gcd , phoD, appA, phnX, phoN) and uptake (pstS, pitA) along a soil depth gradient in a short rotation coppice in Northeast Germany. Potential phosphatase activities and gene abundances revealed increasing potentials for organic P mineralization and high-affinity P uptake via the Pst system in the drilosphere below 50 cm depth. Conversely, in the upper soil layers potential for bacterial P mobilization were similar between drilosphere and bulk soil. We also observed drilosphere-related changes in the composition of bacterial communities involved in P solubilization and low-affinity P uptake via the Pit system below 60 cm depth. In the drilosphere compared to bulk soil, Pseudomonadaceae were enriched and played a major role in solubilization and low-affinity uptake of P, while bacteria potentially involved in N turnover like Bradyrhizobiaceae and Phyllobacteriaceae were less abundant. Our study suggested that earthworms increased the potential enzyme activity and abundance of bacteria carrying the Pho-regulon genes in the drilosphere of the deeper soil layers. Furthermore, earthworm-derived bacteria were enriched in the drilosphere at the same soil depth, especially those involved in P solubilization and carrying the Pit system. • Increased potential for bacterial P mineralization and uptake via the Pst system in the drilosphere below 50 cm depth • Enhanced P turnover potential was highly associated with P scarcity • Earthworm-induced changes in bacterial community composition involved in P solubilization and uptake via the Pit system in subsoil • Earthworm-derived Pseudomonadaceae highly contributed to P solubilization and uptake via the Pit system in the drilosphere subsoil [ABSTRACT FROM AUTHOR]

We introduce an easy, fast and effective method to analyze the influence of genetically modified (GM) plants on soil and model organisms in the laboratory to substitute laborious and time consuming field trials. For the studies described here we focused on two GM plants of the so-called 3rd generation: GM plants producing pharmaceuticals (PMP) and plant made industrials (PMI). Cyanophycin synthetase (cphA) was chosen as model for PMI and Choleratoxin B (CTB) as model for PMP. The model genes are expressed in transgenic roots of composite Vicia hirsuta plants grown in petri dishes for semi-sterile growth or small containers filled with non-sterile soil. No significant influence of the model gene expression on root induction, growth, biomass, interaction with symbionts such as rhizobia (number, size and functionality of nodules, selection of nodulating strains) or arbuscular mycorrhizal fungi could be detected. In vitro , but not in situ under field conditions, structural diversity of the bulk soil microbial community between transgenic and non-transgenic cultivars was determined by PLFA pattern-derived ratios of bacteria: fungi and of gram + : gram − bacteria. Significant differences in PLFA ratios were associated with dissimilarities in the quantity and molecular composition of rhizodeposits as revealed by Py-FIMS analyses. Contrary to field trials, where small effects based on the transgene expression might be hidden by the immense influence of various environmental factors, our in vitro system can detect even minor effects and correlates them to transgene expression with less space, time and labour. [ABSTRACT FROM AUTHOR]

We introduce an easy, fast and effective method to analyze the influence of genetically modified (GM) plants on soil and model organisms in the laboratory to substitute laborious and time consuming field trials. For the studies described here we focused on two GM plants of the so-called 3rd generation: GM plants producing pharmaceuticals (PMP) and plant made industrials (PMI). Cyanophycin synthetase (cphA) was chosen as model for PMI and Choleratoxin B (CTB) as model for PMP. The model genes are expressed in transgenic roots of composite Vicia hirsuta plants grown in petri dishes for semi-sterile growth or small containers filled with non-sterile soil. No significant influence of the model gene expression on root induction, growth, biomass, interaction with symbionts such as rhizobia (number, size and functionality of nodules, selection of nodulating strains) or arbuscular mycorrhizal fungi could be detected. In vitro, but not in situ under field conditions, structural diversity of the bulk soil microbial community between transgenic and non-transgenic cultivars was determined by PLFA pattern-derived ratios of bacteria: fungi and of gram + : gram − bacteria. Significant differences in PLFA ratios were associated with dissimilarities in the quantity and molecular composition of rhizodeposits as revealed by Py-FIMS analyses. Contrary to field trials, where small effects based on the transgene expression might be hidden by the immense influence of various environmental factors, our in vitro system can detect even minor effects and correlates them to transgene expression with less space, time and labour. [ABSTRACT FROM AUTHOR]

Phosphorus losses from agricultural soils are usually predominately caused by surface-runoff and only rarely by tile drain discharge. However, storm events can drastically increase P transfer to water bodies. In 2011 summer storm events caused 3.2 fold higher precipitation compared to the long-term average in Northern Germany. During these storm events excessive yellow-brown ochre flocs were observed in drain discharges and supposed to be potential P carrier. Therefore, water samples with ochre flocs were taken and analyzed by light and electron microscopy and for total elemental concentrations of P and its common binding partners (Al, Fe, Mn). Additionally, sandy sediment samples were taken in winter and analyzed for total and oxalate-extractable amounts of these elements. Water samples with ochre flocs revealed total P concentrations of approximately 27 to 141 mg l −1 . During the high discharge period a cumulative discharge of 124.6 mm from a drain plot of 4.2 ha was recorded, which resulted in a calculated minimum loss of 34 kg P t ha −1 . This was assumed to be promoted by the excessive occurrence of ochre flocs, which were mainly formed by fungal mycelia with precipitated Fe- and Mn-(hydr)oxides at the surface. The poor crystallinity of the Fe-oxides from the discharge of tile drains was confirmed by an amount of up to 94% of active Fe-oxides in the sandy sediment. The extremely high discharge from tile drains, the flocky nature of the ochre along with a poor crystallinity of Fe-oxides and high P concentrations possess the risk of increased input and bioavailability of P in water bodies. Therefore, discharge and P forms from tile drained areas should be monitored more intensively and retention of P on tile drain outlets should be considered to prevent water bodies from eutrophication. [ABSTRACT FROM AUTHOR]

The addition of wood chips as a co-substrate can promote the degradation of oil in soil. Therefore, in the present study, the tree species-specific impact of wood chips of Scots pine (Pinus sylvestrisL.), Norway spruce (Picea abiesL.) and Western balsam poplar (Populus trichocarpaL.) on the degradation of crude oil was tested in beach sand in a 4-week incubation experiment. The CO2-C release increased in the order of control without wood chips < +spruce < +pine < +poplar. Initial and final hydrocarbon concentrations (C10to C40), as indicators for the oil degradation, were determined with gas chromatography-flame ionization detection (GC-FID). The degradation increased for the light fraction (C10to C22), the heavy fraction (C23to C40) as well as the whole range (C10to C40) in the order of control without wood chips (fdegrad.= 23%vs.0%vs.12%) < +poplar (fdegrad.= 49%vs.19%vs.36%) < +spruce (fdegrad.= 55%vs.34%vs.46%) < +pine (fdegrad.= 60%vs.44%vs.53%), whereas the heavy fraction was less degraded in comparison to the light fraction. It can be concluded, that the tree species-specific wood quality is a significant control of the impact on the degradation of hydrocarbons, and pine wood chips might be promising, possibly caused by their lower decomposability and lower substrate replacement than the other wood species. [ABSTRACT FROM AUTHOR]

Assessing the organic C (C org ) sequestration in no-till soils under perennial crops requires molecular-level quality indicators. Therefore, we investigated the quality of soil organic matter (SOM) in the topsoil under Salix viminalis L. and Lolium perenne L. at two test sites in Central Sweden. The willow S. viminalis (clone 78021) was grown in short rotation coppice, and the grass L. perenne in an adjacent meadow for 17 (site Ultuna) and 15 years (site Enköping), respectively. The concentrations of aliphatic lipids, determined by gas chromatography/mass spectrometry (GC/MS), as well as the molecular composition and thermal stability of the bulk SOM, determined by pyrolysis-field ionization mass spectrometry (Py-FIMS), were tested as indicators for the crop-specific SOM quality. Larger C org concentrations (factor 1.4) in the topsoil (site Ultuna) under S. viminalis than under L. perenne corresponded to higher concentrations of summed aliphatic lipids (factor 1.6), mainly saturated n -alkanoic acids (factor 2.1) and n -alkanols (factor 1.5) in the GC/MS-analyses. Moreover, in the willow stand (site Ultuna) at soil depth of 0–10 cm disproportionally higher concentrations of saturated n -alkanoic acids (C 17 –C 36 ) (factor 2.4) and n -alkanes (C 21 –C 36 ) (factor 2.6) indicated a preferential sequestration of aliphatic C because the bulk C org concentrations were only larger by factor 1.4. This crop-specific impact on SOM at soil depth of 0–10 cm was proven for both test sites. Furthermore, the Py-FIMS showed larger abundances of thermally stabile alkylaromatics (factor 1.4), and non-peptidic N-containing compounds (factor 1.3) in the S. viminalis plot (site Enköping), which supported a crop-specific C org -sequestration of these compounds. Thus, in summary, accumulations in extracted long C-chain aliphatic lipids and the thermal stability of some substance classes indicated that the C org sequestration by no-till may be more distinct in soils under S . viminalis than under L. perenne . [ABSTRACT FROM AUTHOR]

"Pan de Azúcar National Park" is a fog oasis in the southern Atacama Desert of Chile. It hosts a diversity of cyanobacteria and green algae, which can especially be found in lichens. Diversity surveys and eco-physiological and biochemical studies have shown that these organisms are excellently adapted to the extreme climate and can already become active even if the amount of water available is very low. By changing their environment physically and chemically, they contribute to the weathering of rocks and soil formation and are thus involved in shaping the landscape. [ABSTRACT FROM AUTHOR]

Potato plants can be colonized by various viruses and by symbiotic, saprophytic and pathogenic fungi. However, the significance of interactions of viral infection and fungal colonization is hardly known. This work presents a model experiment in which the influence of three different types of fungal associations on the growth and physiology of the potato variety Pirol was tested individually or in combination with infection by PVY. It was hypothesized that simultaneous viral and fungal infections increase the biotic stress of the host plant, but mutualistic plant-fungal associations can mask the impact of viral infection. In the present study, a symbiotic arbsucular mycorrhizal fungus, Glomus intraradices, significantly stimulated the growth of plants infected with PVY. In contrast, two saprophytic Trichoderma spp. strains either did not influence or even inhibited the growth of PVY-infected plants. Also, inoculation of PVY-infected potato plants with a pathogenic strain of Colletotrichum coccodes did not inhibit the plant growth. Growth of the PVY-free potato plants was not promoted by the symbiotic fungus, whereas T. viride, T. harzianum and C. coccodes had an evident inhibitory effect. The strongest growth inhibition and highest concentration of H2O2, as an indicator of biotic stress, was observed in PVY-free potato plants inoculated with T. harzianum and C. coccodes strains. Surprisingly, ultrastructural analysis of PVY-infected plant roots colonized by G. intraradices showed virus-like structures in the arbuscules. This pointed to the possibility of mycorrhizal-mediated transmission of virus particles and has to be further examined by testing with immunoassays and real transmission to uninfected plants. In conclusion, although mycorrhiza formation might decrease the impact of PVY infection on plants, a possible role of mycorrhizal fungi as virus vectors is discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tillage of former short rotation coppice leads to a fast and strong redistribution of soil organic carbon in the topsoil. [•] Former short rotation coppice under tilled annual crops has significantly decreased soil aggregate stability. [•] The aggregate stability is more sensible to tillage than the pool size of SOC. [Copyright &y& Elsevier]

Abstract: During the past decade, soil and geochemists have adopted a variety of novel chemical–analytical methods to explore the chemistry of soil organic N (Norg). This chapter summarizes some of the more recent developments in the use of wet-chemical and instrumental methods to determine total Norg concentrations as well as to speciate the Norg in soils. A critical evaluation of 15N nuclear magnetic resonance (NMR) spectroscopy found the technique to be wanting, in terms of its sensitivity and ability to identify classes of Norg compounds in soils. Complementary mass spectrometric techniques are described briefly, and improved data evaluations based on broad applications of high-resolution pyrolysis-field ionization mass spectrometry are presented and discussed. A reassessment of older data sets using the new spectral evaluation algorithms provides strong evidence of fire- and management-induced changes in Norg speciation. Isotope-ratio mass spectrometry, Fourier transform ion cyclotron resonance mass spectrometry, and nanoscale secondary ion mass spectrometry (Nano-SIMS) also are discussed, with the latter two techniques having potential to (1) identify Norg compounds and (2) provide spatially resolved information on the molecular, elemental and isotopic composition of soil Norg. The use of 15N labeling techniques is discussed both from a methodological standpoint and in terms of tracking the fate of plant-derived (residue or rhizodeposit) N in the soil. Indeed, coupling 15N labeling with analytical techniques such as 15N NMR, Nano-SIMS and high- or ultrahigh-resolution mass spectrometry can provide information on how N is incorporated into soil organic matter. Analytical and instrumental innovations have resulted in new insights into the chemistry of Norg—together with a revised summary of the relative amounts of the different Norg compound classes present in soils (e.g. aliphatic amine and amide N, aromatic heterocyclic N), as well as their ecophysiological functions. Particular emphasis is given to the use of multitechnique analyses and the outstanding molecular–chemical diversity of biogenic heterocyclic Norg compounds. Examples are given of the new insights obtained using multi-analytical research approaches to explore microbial utilization of heterocyclic N and organic–mineral interactions, as well as the ability of human and environmental intervention to alter the composition of soil Norg. Finally, we examine future challenges and propose analytical approaches to tackle open questions regarding the basic chemistry and cycling of Norg in soils, as well as the agronomic and environmental consequences associated with N transformations in agro-ecosystems. [Copyright &y& Elsevier]

Fungal colonization can significantly affect the secondary metabolism of the host plants. We tested the impact of a common below-ground symbiosis, i.e., ectomycorrhiza formation, on poplar leaf chemical components that are involved in the defence against a common disease, i.e., rust fungi, in N-deficient soil. A rust-susceptible poplar clone (Populus trichocarpa × deltoides ‘Beaupré’) was (a) non-associated with ectomycorrhizal fungus (EM) Hebeloma mesophaeum (Pers.) Quélet MÜN and non-infected with rust fungus Melampsora larici-populina Kleb. (isolate 98AG31), (b) associated with EM, (c) inoculated with rust fungus and (d) associated with EM and inoculated with rust fungus. Poplar leaves were analysed by photometric and mass spectrometric techniques (liquid chromatography–tandem mass spectrometry (LC-MS/MS), pyrolysis–field ionization mass spectrometry (Py-FIMS)). Both rust infection and mycorrhiza formation led to increased proportions of condensed tannins in relation to total phenolics (13% in the control, 18–19% in the fungal treatments). In contrast, salicylic acid concentration (6.8 µg g−1 in the control) was higher only in the rust treatments (17.9 and 25.4 µg g−1 with rust infection). The Py-FIMS analysis revealed that the rust-infected treatments were significantly separated from the non-rust-infected treatments on the basis of six flavonoids and one lipid. The relative abundance of these components, which have known functions in plant defence, was decreased after rust infection of non-mycorrhizal plants, but not in mycorrhizal plants. The results indicate that the ectomycorrhizal formation compensated the rust infection by a decrease in the flavonoid syntheses. The study provides new evidence for an interactive response of mycorrhizal colonization and infection with rust fungi in the metabolism of poplar. [ABSTRACT FROM AUTHOR]

Abstract: Under changing redox conditions some plants create plaques at their root surface, which may affect the mobility and uptake of As and heavy metals but it is unknown to what extent this also holds true for willows in contaminated floodplain soils. Therefore, willow roots were sampled from a phytoremediation trial in the contaminated floodplain of the river Elbe (Germany), cryofixed, freeze-dried, and cross sections were mapped for the distribution of As, Ca, Cu, Fe, K, Mn, Ni, S and Zn by synchrotron based X-ray fluorescence spectroscopy. The elements Ca, Cu, Ni, S and Zn were concentrated in the aerenchymatic tissue, and not associated with Fe and Mn. Mixed Fe–Mn plaques covered the surface of the willow roots and As was accumulated in these plaques. The observed association pattern between As and Fe was explained by the different sorption/desorption properties of As(III) and As(V). The Cu and Zn intensities were not associated with the intensity of Fe in the plaque, which seems to be a willow-specific difference compared to other wetland plants. These results suggested that willows are especially suited to stabilize low-phytoextractable elements like Cu and As in their roots and rhizosphere. Thus, short rotation coppicing of willows may be a practical approach to mitigate the adverse effects of floodplain soil contamination. [Copyright &y& Elsevier]

Abstract  Biotic interactions affect the impact of potential plant growth promoting microorganisms in the rhizosphere, but their magnitude and fundamentals are often hardly known. In a pot experiment, two physiologically different strains of the ectomycorrhizal fungus Paxillus involutus (GUL and FRA) were tested separately and in combination with associated bacteria (Sphingomonas paucimobilis 1 L, Ralstonia pickettii 16 B, Sphingomonas sp. 23 L) on their effects on the growth of willows (Salix viminalis). Both P. involutus strains significantly increased the growth of the willows compared with non-inoculated plants, but the magnitude of this effect was significantly affected by the fungal strain. The P. involutus strain GUL with higher synthesis of auxin-like substances, acid phosphatases, siderophores and faster utilisation of yeast extract in vitro increased the willow growth in situ more effectively than strain FRA. Additionally, dual inoculation with the P. involutus strains GUL and FRA in combination with the associated bacteria promoted the willow growth, especially the combination with S. paucimobilis 1 L. This bacterial strain used effectively C sources which are common components of plant root exudates, e.g. glucose, sucrose, maltose and mannose as well as compounds synthesized by fungi, e.g. trehalose in vitro. We conclude that the analyses of fungal metabolites and of C source use of associated bacteria can successfully contribute to accelerate the selection of capable plant growth promoting combinations. [ABSTRACT FROM AUTHOR]

Abstract: Relationships between soil organic matter (SOM) molecular composition, thermal stability and decomposability by soil enzymes and microbes are largely unknown. We incubated soils from unfertilized and NPK-fertilized neighboring field plots of a long-term rye (Secale cereale) monoculture experiment and investigated relationships between changes in the molecular-chemical composition of SOM, the CO2 flux and the activities of enzymes. Pyrolysis-field ionization mass spectrometry (Py-FIMS) showed larger ion intensities in the NPK-fertilized than in the unfertilized soil at start of the incubation, only small changes in composition and thermal stability in the unfertilized soil, and a preferential reduction in thermally stable components as well as general shifts towards lower pyrolysis temperature after three weeks of incubation in the NPK-treatment. We found evidence that thermally labile and stable proportions of various compound classes were differently susceptible to decomposition, depending on the fertilization history of the soil. Irrespective of fertilization treatment, peaks in xylanase activity after 7 days of incubation followed by decreasing values were reflected by the ratio of xylan (m/z 114) to xylose (m/z 132) marker signals in the Py-FI mass spectra. Thus, the study proved that (1) SOM composition was changed due to long-term rye cropping without and with NPK-fertilization, (2) the modified SOM composition affected the decomposability and microbial parameters under optimized conditions and (3) the thermal properties of individual compound classes derived from Py-FI mass spectra can be sensitive predictors of microbial decomposition. [Copyright &y& Elsevier]

Abstract: The goat willow (Salix caprea) belongs to the typical pioneer vegetation at former ore mining sites in Middle Europe as a result of its high metal-tolerance. Ectomycorrhizal (EM) fungi are known to contribute essentially to the tolerance of plants against abiotic stress. We investigated the EM associations of S. caprea at three former silver-mining sites around Freiberg (Saxonia, Germany) after 33years of revegetation. The EM colonisation ranged from 3 to 36% of the fine root tips. We found 14 different EM types and characterised them morphologically as well as anatomically. The fungal partners were identified using LSU and ITS sequences. They belonged to four families: Thelephoraceae, Cortinariaceae, Tricholomataceae and Tuberaceae. Thelephoraceae, with 53–91%, comprised the largest portion of the total EM colonisation at all test sites and sampling dates. Thelephoraceae produced mainly contact exploration types of ectomycorrhiza. Tricholoma cingulatum was the only EM fungus which was found as ectomycorrhiza and sporocarp. We suppose that the low exploration of the majority of EM associations of S. caprea, in combination with high portions of metal-chelating organic acids containing fungal partners, contributes essentially to the high tolerance of this tree species against high metal concentrations in the soil. [Copyright &y& Elsevier]

Short rotation forestry is a promising tool for biomass production. In order to determine long-term effects of short rotation forestry on chemical, biochemical and physical soil properties we have investigated two former arable sites with willow and poplar clones (Salix and Populus spp.) in northeast Germany. The organic carbon and the total nitrogen contents of the sandy topsoil increased up to 4.0 g kg-1 and 0.2 g kg-1, respectively after 12 years. The C/N ratio was higher under short rotation forestry caused by the stronger C than N accumulation. The contents and reserves of plant available phosphorus and potassium were decreased significantly from the 6th to the 12th year, but the plant supply was still sufficient without fertilization. The pH in the topsoil was significantly lower under willow clones than under poplar clones. Higher dehydrogenase activity of the soil was measured under poplar and willows than at tree-less control plots. The bulk density decreased and the porosity of the soil increased under short rotation forestry. In conclusion the major long-term effects of short rotation forestry on arable used Cambisols were the accumulation of organic matter followed by slightly improved soil physical conditions and increased soil biological activity. [ABSTRACT FROM AUTHOR]

In mountainous grasslands management adaptations are required to maintain soil functions. We investigated climate change (CC) and management effects on the abundance and potential activity of microbiota catalyzing the major steps of P transformation which are still unknown in these grasslands. Soil samples were taken from intact plant-soil mesocosms managed extensively or intensively (two vs. five mowing and slurry applications, respectively). These mesocosms were previously translocated from high to lower altitudes to simulate two CC scenarios (CC1: +1 °C warming and mean annual precipitation (MAP) of 1347 mm and CC2: +3 °C warming and MAP of 956 mm), while control mesocosms (CC0) were relocated at their original site (6 °C and MAP of 1400 mm). Specific marker genes for P-solubilization (gcd), P-mineralization (phoN , phoD , phnX and appA), P-uptake (pitA and pstS), total bacteria and arbuscular mycorrhizal fungi (AMF) were quantified by quantitative real-time PCR. Spatial distributions of phosphatase activities were analyzed in situ by zymography analysis and total organic C, N and P contents were measured. Gene abundances and enzymatic activities were comparable for both managements under CC0, except for phytase-harboring (appA) microbiota which decreased under intensive management. The abundance of microbiota which catalyzes organic P (Po) mineralization (phoN and appA) and those harboring quinoprotein glucose dehydrogenase (gcd) for P solubilization significantly dropped by interacting effects of CC2 and extensive management. The same effect was found for microbes harboring specific P transporters (pitA and pstS). Under intensive management, microbiota catalyzing Po mineralization (phoN and appA), and alkaline phosphatase activities tended to increase in CC2. Noteworthy, the AMF abundance was reduced at 0–5 cm soil depth under CC. Our results suggest that CC and extensive management reduced microbial P solubilization, mineralization and uptake, while management intensification may increase P availability, which leads to shifts in nutrient stoichiometry and decreased AMF abundance. • Climate change and management affected P mineralizing and solubilizing bacteria. • Higher alkaline phosphatase activity under intensive management and climate change. • Nutrient stoichiometry shifts by climate change and management effect interaction. • Microelement concentration shifts at the soil upper layer by intensive management. • Bacteria and AMF react differently to climate change and management. [ABSTRACT FROM AUTHOR]

Plantations of willow (Salix spp.) are today grown as short-rotation coppice (SRC) for the sustainable production of biomass. While developing these production systems in the past, much ecological knowledge on plant–plant, plant–environment and trophic interactions has been generated. This knowledge can contribute to the further development of biodiversity–ecosystem function (BEF) theory, which frequently lacks a sound understanding of the complex mechanisms behind the observed patterns of diversity-productivity relationships. Thus, willow SRC systems are suitable models to explore BEF theory; they are simple enough to allow the study of the complex ecological mechanisms involved and they have many similarities to grassland systems in which much of recent BEF theory development has been achieved. This paper briefly reviews the current observational and mechanistic knowledge on diversity–productivity relationships in willow SRC, as well as the most important above- and below-ground trophic interactions that are likely to affect them. If the available knowledge is integrated and combined with further experimental work targeting mechanisms behind patterns, research on willow SRC as a model offers a great opportunity for filling the gaps in the understanding what presently hampers the development of predictive BEF theory. [ABSTRACT FROM AUTHOR]

Although cryptogamic covers are important ecosystem engineers in high Arctic tundra, they were often neglected in vegetation surveys. Hence we conducted a systematic survey of cryptogamic cover and vascular plant coverage and composition at two representative, but differing Arctic sites (Ny-Ålesund, Svalbard) along catenas with a natural soil moisture gradient, and integrated these data with physical–chemical soil properties. Soil samples were taken for comprehensive pedological and mineralogical analyses. Vegetation surveys were conducted based on classification by functional groups. Vascular plants were identified to species level. Correlation and multivariate statistical analysis were applied to determine the key environmental factors explaining vegetation patterns along the soil moisture gradients. We observed significant differences in gravimetric water, soil organic matter and nutrient contents along the moisture gradients. These differences were coincident with a shift in vegetation cover and species composition. While chloro- and cyanolichens were abundant at the drier sites, mosses dominated the wetter and vascular plants the intermediate plots. Twenty four vascular plant species could be identified, of which only six were present at both sites. Cryptogamic covers generally dominated with maximum areal coverage up to 70% and hence should be considered as a new additional syntaxon in future ground-truth and remote sensing based vegetation surveys of Svalbard. Multivariate analysis revealed that soil moisture showed the strongest relation between vegetation patterns, together with NH4–N and pH. In conclusion, soil moisture is a key driver in controlling cryptogamic cover and vegetation coverage and vascular plant species composition in high Arctic tundra. [ABSTRACT FROM AUTHOR]

Phosphorus (P) fertilizers and mycorrhiza formation can both significantly improve the P supply of plants, but P fertilizers might inhibit mycorrhiza formation and change the microbial P cycling. To test the dimension and consequences of P fertilizer impacts under maize (Zea mays L.), three fertilizer treatments (1) triple superphosphate (TSP, 21–30 kg P ha−1 annually), biowaste compost (ORG, 30 Mg ha−1 wet weight every third year) and a combination of both (OMI) were compared to a non‐P‐fertilized control (C) in 2015 and 2016. The test site was a long‐term field experiment on a Stagnic Cambisol in Rostock (NE Germany). Soil microbial biomass P (Pmic) and soil enzyme activities involved in P mobilization (phosphatases and ß‐glucosidase), plant‐available P content (double lactate‐extract; PDL), mycorrhizal colonization, shoot biomass, and shoot P concentrations were determined. P deficiency led to decreased P immobilization in microbial biomass, but the maize growth was not affected. TSP application alone promoted the P uptake by the microbial biomass but reduced the mycorrhizal colonization of maize compared to the control by more than one third. Biowaste compost increased soil enzyme activities in the P cycling, increased Pmic and slightly decreased the mycorrhizal colonization of maize. Addition of TSP to biowaste compost increased the content of PDL in soil to the level of optimal plant supply. Single TSP supply decreased the ratio of PDL:Pmic to 1:1 from about 4:1 in the control. Decreased plant‐benefits from mycorrhizal symbiosis were assumed from decreased mycorrhizal colonization of maize with TSP supply. The undesirable side effects of TSP supply on the microbial P cycling can be alleviated by the use of compost. Thus, it can be concluded that the plant‐availability of P from soil amendments is controlled by the amendment‐specific microbial P cycling and, likely, P transfer to plants. [ABSTRACT FROM AUTHOR]

Abstract: Willow (Salix spp.) short‐rotation coppice is commercially grown to produce lignocellulosic biomass to meet renewable bioenergy demands. Most commercial willow coppices are grown in stands of a single genotype, but biomass productivity may be greater in mixed communities, and the productivity in mixed communities may depend on the specific genotypes involved. We assessed the biomass production of four different Salix genotypes (“Björn,” “Jorr,” “Loden,” “Tora”) grown without additional nutrient fertilization during one cutting cycle at three locations in Europe (Uppsala in Sweden, Rostock and Freiburg in Germany) in plots of pure and mixed communities. We evaluated (i) the effect of genotype diversity on shoot biomass productivity, including the evidence for complementarity and selection effects; (ii) the influence of individual genotypes on mixed community productivity; and (iii) the productivity of individual genotypes in response to pure vs. mixed culture. Mean shoot biomass production after the first cutting cycle decreased in the order Rostock (8.7 Mg ha−1) > Freiburg (6.9 Mg ha−1) > Uppsala (5.7 Mg ha−1), with values similar to those for other nonfertilized willow stands after the first growth cycle. Consistently across all three locations, increasing genotype diversity did not significantly affect shoot biomass production. Using Bayesian statistics, the addition of the genotypes “Jorr” and “Loden” was predicted to enhance shoot biomass production, while “Tora” and “Björn” are more likely to reduce shoot biomass production in mixed communities. In addition, we found evidence for a negative selection effect due to the genotype “Tora” performing better in mixed than in pure communities in two of the sites (Freiburg, Uppsala). In conclusion, our results imply that increasing genetic richness has no negative effect on productivity and that there is a potential to design site‐specific genotype mixtures of short‐rotation coppice promoting both high genetic diversity and high biomass production. [ABSTRACT FROM AUTHOR]

Phytoremediation is the bioremediation of contaminated soils and waters by using plants and their associated microorganisms. Phytoremediation of heavy metal (HM)-contaminated soils is based on immobilization of metals in rhizosphere soil and roots (phytostabilization) and on mobilization, uptake, and transfer of metals into the aboveground plant organs (phytoextraction). In this review, we aimed to (i) discuss the fundamentals, potential, and limitations of plant-associated microorganisms (bacteria and fungi) to increase the efficiency of phytostabilization and phytoextraction of HM-contaminated soils and (ii) describe promising developments and future challenges to expanding their use. Controlled inoculations of plants with growth-promoting microorganisms can significantly increase their root growth, biomass production, and stress tolerance in HM-contaminated soils. A serious weakness of phytoremediation in general is the usually high and difficult to measure expenditure of time for successful completion. The bioconcentration factors (BCFs) and the translocation factors (TFs) are among the most important measures of the efficiency of phytoremediation. However, an overview of BCFs and TFs for a variety of combinations of plants with defined associated microorganisms is lacking. Moreover, the joint evaluation of model systems would allow an improved cost–benefit calculation of microbial inoculations in phytoremediation systems. For this purpose, the use of in vitro model systems is considered to be preferable to field experiments due to the savings in time and costs and the control of environmental conditions. However, the transferability of in vitro data to field conditions is limited. Currently, attention is focused on the use of artificial neural networks, mainly to avoid formulating any complex relationships between soil inputs (e.g., soil amendments, pH, carbon, nitrogen and hydrogen contents, electrical conductivity, and dissolved organic carbon) and design outputs (e.g., BCFs and TFs) beforehand and because of the high accuracy of the obtained models. The controlled use of associated microorganisms to increase the efficiency of phytoremediation of HM, mainly using combinations of Brassica and Salix spp. and rhizobacteria at contaminated soils, is a promising possibility. A crucial future challenge for the expansion of their use will be to develop well-defined cost- and time-efficient tools for a credible prediction of their effectiveness on contaminated field sites. [ABSTRACT FROM AUTHOR]

Summary: Phosphorus is one of the most important macronutrient for plants. In agriculture, amending fertilizer with phosphorus (P) is common practice. However, natural phosphorus sources are finite, making research for more sustainable management practices necessary. We postulated that the addition of carbon (C) and nitrogen (N) would stimulate phosphorus mobilization by bacteria because of their desire to maintain a stable intracellular C:N:P stoichiometry. Therefore, we chose a metagenomic approach to investigate two agricultural soils, which only received mineral N fertilizer or mineral N and organic fertilizer for more than 20 years. The most abundant genes involved in the acquisition of external P sources in our study were those involved in solubilization and subsequent uptake of inorganic phosphorus. Independent of site and season, the relative abundance of genes involved in P turnover was not significantly affected by the addition of fertilizers. However, the type of fertilization had a significant impact on the diversity pattern of bacterial families harbouring genes coding for the different P transformation processes. This gives rise to the possibility that fertilizers can substantially change phosphorus turnover efficiency by favouring different families. Additionally, none of the families involved in phosphorus turnover covered all investigated processes. Therefore, promoting bacteria which play an essential role specifically in mobilization of hardly accessible phosphorus could help to secure the phosphorus supply of plants in soils with low P input. [ABSTRACT FROM AUTHOR]

Trace elements (TEs) are deposited to soils mainly due to anthropogenic activities and pose a significant threat to human health. In this review we aimed at (a) discussing the phytoavailability of TEs as affected by various soil parameters, and by plant defense mechanisms related to uptake and translocation; (b) examining soil and plant indices related to TE phytoavailability; (c) clarifying the challenges and problems related to phytoremediation; and (d) exploring the often encountered discrepancies of lower-than-expected TE toxicity. We particularly discussed the soil-to-plant availability index (transfer coefficient, TC ), because it encompasses all soil and plant factors related to TE phytoavailability. As for soil, we explored the effect of pH, redox potential, clay and organic matter contents, as well as aging of added elements. The latter is a key factor in interpreting the observed lower-than-expected toxicity to plants in real field conditions. This is because the discrepancy is very often generated by growth experiments that expose plants to TEs directly from TE-laden solutions or by studies that spike soils with TEs only days or weeks before planting. Also, the behavior of TEs depends on the nature and quantity of TEs. As for plant, TE absorption or exclusion is highly related to species-specific defense mechanisms developed by plants so that they are exposed to TE-induced stress. These mechanisms address TE exposure by operating both outside and inside the plant body; outside with the assistance of root exudates, and the rhizosphere microflora, and inside with selective translocation and storage processes. The absorption/exclusion behavior of plants also depends on root activities and related soil chemical processes which are highly localized within a spatial scale of a few mm from roots. Novel techniques for the imaging of TE biogeochemistry at the root-soil interface are therefore addressed and their explanatory power is demonstrated. Such plant behavior greatly affects phytoremediation, a process which also depends on the maximal TE uptake capacity of plants, especially of hyperaccumulators. However, phytoremediation also greatly depends on plant biomass yield, an important factor in determining the time required to complete the procedure. In conclusion, soil factors, as well as plant- and TE- related issues, may create discrepancies in TE phytoavailability and phytoremediation that need to be thoroughly understood and addressed. [ABSTRACT FROM AUTHOR]

Biological soil crusts (BSCs) occur in arid and semi-arid regions worldwide including the Polar Regions. They are important ecosystem engineers, and their composition and areal coverage should be understood before assessing key current functional questions such as their role in biogeochemical nutrient cycles and possible climate change scenarios. Our aim was to investigate the variability of BSCs from Arctic Svalbard and the Antarctic Island, Livingston, using vegetation surveys based on classification by functional group. An additional aim was to describe the structure of BSCs and represent a classification system that can be used in future studies to provide a fast and efficient way to define vegetation type and areal coverage. Firstly, this study demonstrates huge areas occupied by BSCs in Arctic Svalbard, with up to 90 % of soil surface covered, dominated by bryophytes and cyanobacteria, and showing an unexpectedly high variability in many areas. Livingston Island has lower percentage coverage, up to 55 %, but is dominated by lichens. Our findings show that both Polar Regions have varied BSC coverage, within the sites and between them, especially considering their harsh climates and latitudinal positions. Secondly, we have classified the BSCs of both areas into a system that describes the dominant functional groups and local geography, creating a simple scheme that allows easy identification of the prevailing vegetation type. Our results represent the first contribution to the description of BSCs based on their functional group composition in Polar Regions. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) is an endocrine disruptor compound widespread in terrestrial and aquatic systems of urbanized and industrialized regions. This study evaluated the capacity of ryegrass(Lolium perenne)aqueous exudates to degrade BPA at a concentration of 10 mg L−1both in the absence and in the presence of an organic fraction often coexisting with plant exudates, i.e., natural organic matter (NOM), tested at a concentration of 20 mg L−1. In exudates alone, BPA degradation ceased after one day from the product addition when residual BPA resulted 65% of the initial BPA, whereas in exudates with the addition of NOM the degradation process continued for 4 days when residual BPA resulted 49%. Measurements of peroxidase and laccase activities in exudates suggested a significant involvement of these enzymes in BPA degradation. This finding was further confirmed by the almost complete absence of BPA degradation in aqueous exudates strongly acidified. In some BPA-contaminated exudates, chromatographic analysis revealed the presence of a newly formed compound identified as a BPA oxidation product by Fourier transform - ion cyclotron resonance mass spectrometry analysis. In conclusion, ryegrass exudates possess a relevant decontamination capacity towards BPA which persists and appears to be enhanced by the addition of NOM. [ABSTRACT FROM PUBLISHER]

The conversion of agriculture land to short rotation coppice (SRC) systems with hybrid poplar (Populus spp.) is becoming an important practice to store carbon and produce biomass for the fiber industry. This land-use change is likely to affect the microbial community structure, in part through the introduction of an ectomycorrhizal host, but also by changing organic matter inputs, ultimately shifting the molecular composition of soil organic matter (SOM) because these properties are crop-specific. The objective of this study was to examine the effect of different aged poplar stands growing on Orthic Gray Luvisols on these soil properties compared to an adjacent perennial crop. The site consisted of four treatments: hybrid poplar (Populus deltoides × Populus petroskyana) in SRC of 7 and 14 years age (Pop7 and Pop14), a 40-year-old aspen (Populus tremuloides) forest (Aspen), and an adjacent arable site with alfalfa (Medicago sativa). The molecular composition of SOM was determined using pyrolysis-field ionization mass spectrometry (Py-FIMS) and synchrotron-based X-ray absorption near edge spectroscopy at the nitrogen (N) K-edge (N-XANES). Phospholipid fatty acid (PLFA) profiles revealed higher concentrations of fungal but not bacterial biomarkers in poplar plantations than under alfalfa. Fungal:bacterial ratio was lower under alfalfa than under poplar trees. Overall microbial community structure also changed in response to vegetation type and the duration of woody biomass. Along the chronosequence of poplar, Py-FIMS revealed significant increases in the proportions of carbohydrates with pentose and hexose subunits, phenols and lignin monomers, alkylaromatics and peptides and significant decreases in lipids, alkanes, alkenes, bound fatty acids and alkylmonoesters and free fatty acids with increasing poplar stand age. Thermal stability of sterols decreased along the chronosequence, suggesting that poplar plantations are not involved in the build-up of these substances. Differences in the ordination were well reflected by N K-edge XANES spectra. Increased carbohydrate portions indicated a significant impact of the ectomycorrhizal host poplar on the molecular composition of SOM in arable soils. Our results demonstrate that a change in land-use from agricultural cropping to woody biomass caused shifts in microbial community structure that were lagged by a shift in SOM chemistry. These shifts impact soil functioning and should be considered in future land management strategies when SRC are harvested. [ABSTRACT FROM AUTHOR]

Legume catch crops can enhance soil fertility and promote the N and P supply of the subsequent main crop, especially with low mineral fertilizer use. However, the specific impact of catch crops on arbuscular mycorrhiza formation of the following main crop is unknown. Therefore, the impact of serradella (Ornithopus sativus) vs. bare fallow was tested on mycorrhiza formation, potential soil enzyme activities and plant-available P under subsequently grown barley (Hordeum vulgare) and different fertilization treatments (P-unfertilized—P0; triple superphosphate—TSP; compost—COM; combined—COM + TSP) in a long-term field experiment in northeastern Germany. Catch cropping significantly increased mycorrhiza formation of barley up to 14% compared to bare fallow. The impact of serradella on mycorrhiza formation exceeded that of the fertilization treatment. Serradella led to increased phosphodiesterase activities and decreased ß-glucosidase activities in soil. Plant availability of P was not significantly affected by serradella. These findings provide initial evidence that even serradella as a non-host crop of mycorrhizal fungi can promote the mycorrhiza formation of the subsequent crop and P mobilization in soil. We conclude that the prolonged vegetation cover of arable soils by the use of catch crops can promote P mobilization and transfer from P pools to the following main crops. [ABSTRACT FROM AUTHOR]

Short rotation coppice (SRC) systems can play a role as feedstock for bioenergy supply contributing to EU energy and climate policy targets. A scenario depicting intensive arable crop cultivation in a homogeneous landscape (lacking habitat structures) was compared to a scenario including SRC cultivation on 20 % of arable land. A range of indicators was selected to assess the consequences of SRC on soil, water and biodiversity, using data from the Rating-SRC project (Sweden and Germany). The results of the assessment were presented using spider diagrams. Establishment and use of SRC for bioenergy has both positive and negative effects. The former include increased carbon sequestration and reduced GHG emissions as well as reduced soil erosion, groundwater nitrate and surface runoff. SRC can be used in phytoremediation and improves plant and breeding bird biodiversity (exceptions: grassland and arable land species) but should not be applied in dry areas or on soils high in toxic trace elements (exception: cadmium). The scenario-based analysis was found useful for studying the consequences of SRC cultivation at larger scales. Limitations of the approach are related to data requirements and compatibility and its restricted ability to cover spatial diversity and dynamic processes. The findings should not be generalised beyond the representativeness of the data used. [ABSTRACT FROM AUTHOR]

Phosphorous (P) is one of the most critical macronutrient elements for plant growth, yield and quality. However, natural P sources are finite and an improved P recycling is necessary. Therefore, we investigated the effect of bone char (BC) and bone char plus (BCplus) as recycling products and alternative P fertilizers, on the abundance of microorganisms, which catalyze major steps in P turnover in a field experiment in Central Germany. The effects were compared to conventional triple super phosphate (TSP) and no P fertilization. Samples were analyzed from soils with three different initial soil P concentrations (very low, low, optimal) and three times during winter wheat cultivation (stem elongation, heading, ripening) to reveal interactions of fertilizers and soil properties. Abundances of microorganisms involved in P uptake, solubilization and mineralization were assessed by quantitative real time PCR (qPCR). Additionally, potential acidic- and alkaline phosphatase activity, water extractable P and plant available P were measured. Bacterial strategies to maintain P pools differed among the treatments. While the addition of BCplus increased the solubilization potential, the low P concentration in control plots and slow release of P from BC favor P recycling from biomass and P inducible uptake systems, which is displayed by either high abundance bacteria harboring the phoD or pstS gene, respectively. All effects were most pronounced at the time of heading and in soils with optimal initial P concentration. It can be assumed that sulfurization of bone char (BCplus) influences bacterial P turnover by promoting solubilization of the fertilizer thereby increasing P availability for plants. Additionally, plant development stage and initial soil P concentrations hamper the effect of BC and BCplus on bacterial P turnover. • Surface-modified bone char (BCplus) stimulates P solubilizing bacteria. • BC fertilization favors the recycling of P from the bacterial biomass. • fertilization effects were strongly interrelated with plant growth stage and initial soil P concentrations. [ABSTRACT FROM AUTHOR]

• Icelandic biocrusts were P-rich though microbial P constituted <0.2% of total P. • Moderately labile P was predominant in biocrusts across the sites. • Eukaryotic microalgae including diatoms dominated Icelandic biocrusts. • Cyanobacteria in the biocrusts were mostly filamentous forms. • Majority of fungi isolated from the biocrusts belonged to Ascomycota and Mucoromycota. Icelandic biocrusts are unique micro-ecosystems, considering their origin from volcanic material as a mineral base. However, little is known about their chemistry and diversity of microorganisms. Being phosphorus (P)-rich, Icelandic soils contribute to the global P cycling. Therefore, here, we focused on investigating P content, P pools, microbial biomass P (P mic) and potential phosphatase activity along an altitude gradient (11–157 m a.s.l.) stretching away from the sea coast. Total P (P total) content in the studied biocrusts and soils varied between 982 and 1571 mg kg−1 and P mic , measured in biocrusts, constituted only a minor fraction <0.2% of P total. Sequential P fractionation revealed the dominance of moderately labile P in biocrusts across the sites. Additionally, basic physicochemical properties were measured in biocrusts, and contents of total carbon (TC) and total nitrogen (TN) were positively correlated to P mic and potential phosphatase activity. Diversity and abundance of microbial phototrophs in the studied biocrusts were assessed by morphological observations using light and epifluorescence microscopy. Microphototrophic communities were dominated by eukaryotic microalgae (e.g. Chlorella , Coccomyxa , Stichococcus) including diatoms (e.g. Pinnularia and Eunotia) and the highest cell biovolume was recorded in the site located at the sea coast. Furthermore, the majority of cyanobacteria belonged to filamentous forms, such as Microcoleus , Leptolyngbya , Phormidesmis and Stenomitos. In addition, the majority of fungal strains isolated from the studied biocrusts belonged to Ascomycota (e.g. Penicillium , Fusarium , Truncatella) and Zygomycota (e.g. Mucor , Mortierella). Overall, this study provides for the first time a comprehensive description of microbial community composition and P distribution in Icelandic biocrusts, which were previously overlooked. [ABSTRACT FROM AUTHOR]

This correction stands to the correct a spelling error to contributor name: Karin Glaser. The author group and the publisher wish all to recognize the name as Karin Glaser and not the former. The original article has been corrected. [ABSTRACT FROM AUTHOR]