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Invasive species are considered a serious threat to local biodiversity and ecosystem functioning. Invasive success is often dictated via a plant's capacity to influence belowground processes. We considered the role of two invasive plants--Solatium elaeagnifolium Cav, a perennial, and Conyza bonariensis L, an annual species--on the rhizosphere soil microbial communities and soil functionality. This study included the cultivation of each of the invasive species and bare soil as a control, in a mesocosm experiment. Rhizosphere soil was collected at three samplings during plant growth. Phospholipid fatty acids and the activities of [beta]-glucosidase, N-acetylglucosaminidase, urease, peroxidase, polyphenol oxidase and acid phosphomonoesterase were analysed. Soil planted with invasive plants exhibited different enzyme activities and microbial biomasses compared with controls. Also, the plant species had soil enzyme profiles that differed from each other, mostly at the vegetative stage, lesser at the maturity stage, with no difference recorded at the middle of the annual cycle. The differences between plant species were significant for microeukaryotes, actinomycetes and the fungi/bacteria and [Gram.sup.-]positive/[Gram.sup.-]negative bacteria ratios but not significant for total microbial biomass and biomasses of [Gram.sup.-]positive and -negative bacteria and fungi in all samplings. The network of interactions among the microbial community and enzymes was affected by plant presence, plant species as well as plant growth stage. This study suggests that life-cycle stage is important in relation to invasive species influence on belowground processes. Keywords: invasive species, plant-microbe interactions, soil enzyme activity, soil microbial biomass., Introduction Biological invasions of exotic species are considered to be among the most serious threats to local biodiversity and ecosystem functioning (Mooney and Hobbs 2000), as they can threaten the [...]

We aimed to explore how the invasion of the alien plant Solanum elaeagnifolium affects soil microbial and nematode communities in Mediterranean pines (Pinus brutia) and maquis (Quercus coccifera). In each habitat, we studied soil communities from the undisturbed core of both formations and from their disturbed peripheral areas that were either invaded or not by S. elaeagnifolium. Most studied variables were affected by habitat type, while the effect of S. elaeagnifolium was different in each habitat. Compared to maquis, the soil in pines had higher silt content and lower sand content and higher water content and organic content, supporting a much larger microbial biomass (PLFA) and an abundance of microbivorous nematodes. The invasion of S. elaeagnifolium in pines had a negative effect on organic content and microbial biomass, which was reflected in most bacterivorous and fungivorous nematode genera. Herbivores were not affected. In contrast, in maquis, organic content and microbial biomass responded positively to invasion, raising the few genera of enrichment opportunists and the Enrichment Index. Most microbivores were not affected, while herbivores, mostly Paratylenchus, increased. The plants colonizing the peripheral areas in maquis probably offered a qualitative food source to microbes and root herbivores, which in pines was not sufficient to affect the much larger microbial biomass. [ABSTRACT FROM AUTHOR]

We investigated the variations in space and time of soil functionality in a Mediterranean serpentine soil for heavy metal and nutrient concentrations, microbial biomass and soil enzymatic activities (urease, dehydrogenase and alkaline phosphatase) in the rhizospheres of different plant species and in bare soil, during the humid and dry seasons of the year. Nutrients and heavy metals were also estimated in leaves of shrubs inhabiting the study area. Four species of serpentine-tolerant shrubs were present: the cvergreen-sclerophyllous Juniperus oxycedrus and Buxus sempervirens and the phryganic Cistus creticus and Thymus sibthorpii. The most significant differentiation of the soil environment was between bare and rhizosphcrc soil, and was mainly driven by the availability of potassium. Spatial variations related to plant identity were clear but less important than temporal variations. There was no relationship between soil and foliar concentrations of nutrients and heavy metals. Higher foliar concentrations were recorded in the phryganic species. Finally, there was no enzyme inhibition due to the heavy metal load of the serpentine soil. Enzymatic activities were lower for bare soil samples, while their temporal variations probably followed the temporal variations of temperature and humidity imposed by the Mediterranean climate. Additional keywords: enzyme activities, heavy metals, microbial biomass, soil nutrients, ultramafic soil. Received 9 October 2015, accepted 3 March 2016, published online 22 August 2016, Introduction Serpentine ecosystems develop on ultramatic soils that exhibit a series of characteristics, which together constitute the so-called 'serpentine syndrome'. The latter refers to the deficiency of serpentine soils in [...]

Managing olive mill wastewater (OMW) is a major environmental problem. We followed two methods for OMW bioremediation: one with the white-rot fungus Pleurotus ostreatus alone and one with the fungus plus the microalga Chlorella vulgaris. To evaluate the potential use of both final products as soil amendments, in a pot experiment, we applied treated OMW to soil cultivated with Lactuca sativa, and we studied their short-term effects on the soil nematode community in terms of trophic and functional structure, metabolic footprint, genera composition, and interaction networks. We also applied non-treated OMW and simply water (control). The addition of non-treated OMW significantly reduced the abundance of all nematodes, and the network of interactions was the most fragmented and the least robust against future disturbance. The effect on trophic group abundances was similar but less pronounced when OMW was previously detoxified either by the fungus alone or by its combination with the alga. In the latter case, the phytoparasites were suppressed but the bacterivorous nematodes were not affected. However, the most cohesive and robust nematode network was formed in the soil that received the fungal-treated OMW. None of our OMW applications significantly changed community composition, none improved the already degraded status of the soil food web—which is attributed to the sandy texture of our soil—and none affected the growth of lettuce plants, perhaps because of the short duration of the experiment (30 days). Thus, our future research will aim to estimate the long-term impact of OMW. [ABSTRACT FROM AUTHOR]

Abiotic and biotic components of a serpentine Mediterranean soil were studied in terms of heavy metal and nutrient concentrations, microbial biomass, and structural and functional characteristics of the soil nematode community. We explored differentiations of the soil environment imposed by vegetation, sampling the bare soil and soil under Buxus sempervirens, Juniperus oxycedrus, Cistus creticus and Thymus sibthorpii. Organic matter, microbial biomass, nutrient availability and calcium/magnesium (Ca/Mg) ratio of the serpentine site were similar to those of degraded, non-serpentine Mediterranean ecosystems; the serpentine site showed potassium deficiency and high heavy metal load. Soil nematode abundance, especially of phytoparasites, was very low. Low enrichment and structure indices and high channel index values indicated a degraded, low-resource, stressful environment where fungal decomposition predominates. There was no differentiation of heavy metal concentrations among microsites. Bare soil exhibited high pH, low water content, low Ca/Mg (0.68), low nutrient concentrations, low abundance of most nematode groups, low values of maturity and plant parasitic indices, low nematode diversity and a distinct generic composition. Rhizosphere soil was differentiated according to the evergreen--sclerophyllous or seasonal-dimorphic habit of shrubs. This was reflected in soil nutrients and in all parameters of the soil nematode community. Additional keywords: Greece, heavy metals, maquis, nematode functional profile, phrygana, ultramafic soil., Introduction Serpentine soils are hostile to the growth of most plants. They are natural metalliferous environments, inheriting minerals from their parent ultramafic rocks. These rocks originate more directly from the [...]

Biological soil crust (BSC) is an essential part of arid and semiarid regions; however information concerning the spatial heterogeneity of the interactions between crust, plants and soil microbes is limited. Sampling was confined to an area either covered with Erica spp. shrubs interspaced by crust cover (Cladonia rangiformis) or uncovered by crust. Along a straight line of 100 cm from the base of the shrubs towards their periphery and at successive distances of 20 cm, soil samples were collected once. The biomass, the composition and the network of interactions among the members of the soil microbial communities as well as the activity of soil enzymes involved in the C, N and P cycle were estimated. Crust coverage exerted a significant allelopathic negative effect on soil microbial biomasses due to the leaching of lichen's antimicrobial substances. In contrast, the crust effect on enzyme activity was positive, probably due to the amelioration of soil abiotic conditions. The distance from the base of Erica spp. affected the total microbial and bacterial biomass, with lower values at the base of the shrubs. The composition of microbial communities between the different sampling points exhibited significant dissimilarities. Network analysis revealed that in uncrusted soils the most connected microbial network was at samples collected from a distance of >60 cm (bare soils), while in crusted soils this was at samples collected at the base of shrubs. We concluded that microbial biomass showed limited response to spatial heterogeneity, while the composition and the topology of interactions among the microbial members reflected a heterogeneous soil environment existing on a small spatial scale in Mediterranean areas. The microbial community in bare soil appeared to be the most robust against future disturbances. [ABSTRACT FROM AUTHOR]

Most species of Cucurbitaceae respond favorably to irrigation, especially when combined with fertilizers. The effect of drip irrigation combined with nitrogen fertigation in melon grown on a very light soil in Central Poland, during 2013–2015, was evaluated. The field experimental design was a split-plot with four replications. Two factors were studied: (1) irrigation treatments applied in two combinations—drip irrigation + broadcast nitrogen fertilization (control), and drip irrigation + fertigation with nitrogen; (2) two cultivars—Melba and Seledyn. The total marketable yield of fruits, weight of a single fruit, and the concentration of dry matter, total sugars, monosaccharides, ascorbic acid, total carotenoids, and polyphenols were evaluated. Tested factors presented a significant effect both on the yield and nutritive value characteristics. Drip irrigation combined with nitrogen fertigation, comparing to the control, notably improved yields and nutritional value of fruits. Seledyn produced better yields than Melba. This study shows that on very light soil, with low water and nutrient retention capacity, melon should be drip-irrigated and nitrogen-fertigated to obtain the best cultivation results. [ABSTRACT FROM AUTHOR]

In modern days, rapid urbanisation, climatic abnormalities, water scarcity and quality degradation vis-à-vis the increasing demand for food to feed the growing population necessitate a more efficient agriculture production system. In this context, farming with zeolites, hydrated naturally occurring aluminosilicates found in sedimentary rocks, which are ubiquitous and environment friendly, has attracted attention in the recent past owing to multidisciplinary benefits accrued from them in agricultural activities. The use of these minerals as soil ameliorants facilitates the improvement of soil's physical and chemical properties as well as alleviates heavy metal toxicity. Additionally, natural and surface-modified zeolites have selectivity for major essential nutrients, including ammonium (NH4+), phosphate (PO42−), nitrate (NO3−), potassium (K+) and sulphate (SO42−), in their unique porous structure that reduces nutrient leaching. The slow-release nature of zeolites is also beneficial to avail nutrients optimally throughout crop growth. These unique characteristics of zeolites improve the fertilizer and water use efficiency and, subsequently, diminish environmental pollution by reducing nitrate leaching and the emissions of nitrous oxides and ammonia. The aforesaid characteristics significantly improve the growth, productivity and quality of versatile crops, along with maximising resource use efficiency. This literature review highlights the findings of previous studies as well as the prospects of zeolite application for achieving sustenance in agriculture without negotiating the output. [ABSTRACT FROM AUTHOR]

The interaction of genotype by the environment is very common in multi-environment trials of maize hybrids. This study evaluates the quantity and the quality of grain production and the stability of four maize genotypes in a field experiment that was conducted in five different locations for two years. In order to make a reliable evaluation of the performance of genotypes in the environments, principal components analysis (PCA) was used to investigate the correlation of the yield, soil properties and quality characteristics, while the additive main effects and multiplicative interaction (AMMI) analysis detected the narrow adaptations of genotypes at specific mega-environments. For the yield, AMMI analysis indicated that a group of five environments (ENV1, ENV8, ENV6 ENV10 and ENV9) gave higher yields than the mean value and at the same time had low first interaction principal components axis (IPC1) scores, indicating small interactions. Regarding protein and fiber contents, ENV1 and ENV2, gave the highest values and this could be attributed to the high concentration rates of nutrients like Mg, Ca and the soil texture (C). Specifically for the protein, the results of the analysis indicated that certain environment would provide more protein content, so in order to obtain higher grain protein, growers should grow in certain locations in order to improve the content of this quality characteristic, certain genotypes should be used in certain environments. [ABSTRACT FROM AUTHOR]

The arbuscular mycorrhizal fungi (AMF) and the essential oils are both agents of sustainable agriculture, and their independent effects on the community of free-living soil microbes have been explored. In a tomato pot experiment, conducted in a sandy loam mixture, we examined the independent and joint effects of inoculation with the fungus Rhizophagous irregularis and the addition of Mentha spicata essential oil on the structure of the soil microbial community and the activity of soil enzymes involved in the N-cycle, during the pre-symbiosis phase. Plants were grown for 60 days and were inoculated with R. irregularis. Then pots were treated with essential oil (OIL) weekly for a period of a month. Two experimental series were run. The first targeted to examine the effect of inoculation on the microbial community structure by the phospholipid fatty acids analysis (PLFAs), and enzyme activity, and the second to examine the effects of inoculation and essential oil addition on the same variables, under the hypothesis that the joint effect of the two agents would be synergistic, resulting in higher microbial biomass compared to values recorded in singly treated pots. In the AMF pots, N-degrading enzyme activity was dominated by the activity of urease while in the non-inoculated ones by the activities of arylamidase and glutaminase. Higher microbial biomass was found in singly-treated pots (137 and 174% higher in AMF and OIL pots, respectively) compared with pots subjected to both treatments. In these latter pots, higher activity of asparaginase (202 and 162% higher compared to AMF and OIL pots, respectively) and glutaminase (288 and 233% higher compared to AMF and OIL pots, respectively) was found compared to singly-treated ones. Soil microbial biomasses and enzyme activity were negatively associated across all treatments. Moreover, different community composition was detected in pots only inoculated and pots treated only with oil. We concluded that the two treatments produced diverging than synergistic effects on the microbial community composition whereas their joint effect on the activity of asparaginase and glutaminase were synergistic., Competing Interests: Conflict of Interest: All authors declare no conflicts of interest in this paper.