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In 2013–2014, the soil mite communities from six overgrazed grassland ecosystems located in the Trascău Mountains, Romania, were investigated. Forty-six species were identified, with 645 individuals. Some abiotic factors from soil were measured (soil temperature – T, soil water content – H, soil acidity – pH, carbon content – C, total nitrogen – Nt, and C/Nt ratio). Significant statistical differences were obtained between environmental factors. Using a canonical correspondence analysis of mite species abundance, environmental variables and habitats, strong relationships between investigated factors were established. [ABSTRACT FROM AUTHOR]

For the first time in Romania, a complex study was conducted on soil mite communities from two types of managed grasslands: ungrazed and intensively grazed. The study was accomplished in August 2018, in the Făgăraş Mountains. Within the soil mite communities (Mesostigmata), 30 species were identified, from 80 soil samples. The following population parameters were investigated: species richness, numerical abundance, dominance, Shannon index of diversity, evenness and equitability. Eight environmental variables were also measured: soil and air humidity; soil and air temperature; soil pH; resistance of soil to penetration; soil electrical conductivity; and vegetation coverage. The results revealed that species richness, Shannon index of diversity, evenness and equitability indices had higher values in ungrazed grasslands, whereas in intensively grazed areas, the numerical abundance and dominance index had significantly higher values. The species Alliphis halleri was dominant in the ungrazed grasslands. Each type of managed grassland was characterised by specific environmental conditions, which had an important influence, even at the species level.

The main objective of the study was to analyse, for the first time in Romania, the relationships between five experimental grasslands and Mesostigmata fauna, considering: (1) the structural differences between mite communities; (2) the variations in some important abiotic factors (vegetation cover, soil temperature, soil moisture content, pH, soil resistance at penetration); and (3) the influence of these abiotic factors on the structures of Mesostigmata mite communities and the dispersal rates of these communities between the investigated plots. In total, 250 soil samples were analysed in July 2017, revealing the presence of 30 species, with 1163 individuals. Using the multivariate analysis, we observed that each experimental plot was defined by characteristic environmental conditions, i.e., vegetation cover, soil moisture content, and soil temperature differed significantly between the experimental grasslands. Each experimental plot was characterised by a specific indicator species and population parameters (numerical abundance and species richness). The effects of these soil variables were even demonstrated at species level: Veigaia planicola , Geolaelaps nolli, and Gamasellodes insignis were influenced by vegetation cover, Lysigamasus conus and Dendrolaelaps foveolatus by soil temperature. The dispersal rates of mite communities from one plot to another were higher in the grasslands, where there were euconstant-constant species.

An anthropic ecosystem from Romania was investigated from acarological, vegetation and chemical point of view. The community structures of two groups of mites were studied (Acari: Mesostigmata, Oribatida) from a tailing pond, using transect method, in correlation with concentrations of heavy metals (As, Cu, Pb, Ni, Mn and Zn), with abiotic factors (altitude, aspect, soil temperature, soil humidity, soil pH) and biotic factor (vegetation coverage). Taking into account the mite communities, in total, 30 mite species were identified, with 1009 individuals and 18 immatures (10 species with 59 individuals, 5 immatures of Mesostigmata and 20 species with 950 individuals, 13 immatures of Oribatida). The investigated habitats from the tailing pond were grouped in five transects, with different degree of pollution, based on total metal loads. Taking into account of the connection between mites communities, abiotic factors and heavy metals, each transect were characterized through specific relationship. Using multivariate statistical analysis, we revealed that the occurrence of some Oribatida species was strongly correlated with vegetation coverage, soil pH and soil humidity, though concentrations of Cu, As, Mn, Ni and Zn also had an influence. Pb and Zn concentrations were shown to influence the occurrence of Mesostigmata mites. The heterogeneity of mites species richness at 2 m 2 scale was correlated with a metric related to the heterogeneity of heavy metals at the same scale.

The data set consists in a file with two sheets: one includes a matrix of 297 rows and 46 columns, and the second one a matrix of 12 rows and 24 columns. In the first sheet each row is a replicate of an experimental variant with Agrostis capillaris growing on tailing substrate belonging to three experiments witch have the same variants, but are organized at three scales. The data from all experiments are in the same table, with a column indicating by a code the experiment to which they belong. In the second spreadsheet there is a table with the relative plant species cover in the experimental field plots. Experimental design and interpretation of the data are provided in "Implications of spatial heterogeneity of tailing material and time scale of vegetation growth processes for the design of phytostabilisation" [1]., (© 2019 The Authors.)

Phytostabilisation projects for tailing dams depend on processes occurring at spatial scales of 10 6  m 2 and at decadal time scales. Most experiments supporting the design and monitoring of such projects have much smaller spatial and time scales. Usually, they are only designed for one single scale. Here, we report the results of three coupled experiments performed at pot, lysimeter and field plot scales using six sampling periodstimes from 3 to 20 months. The work explicitly accounts for the sampling times when evaluating the effects of amendments on the performance of plants grown in tailing substrates. Two treatments with potentially complementary roles were applied: zeolites to decrease availability of Cd, Cu, Pb and Zn and green fertilizer to increase the availability of nutrients. Zeolites have a positive influence on plant development, especially in the early stages. Analyses of the pooled datasets for all sampling times revealed the possibility of predicting plant physiological variables, such as protein concentrations, pigments and oxidative stress enzyme activities, as a function of the factors extracted by principal component analysis from the metal concentrations in plants, phosphorus concentrations in plants, and sampling times. Two potentially general methodological rules were extracted: account for the spatial geochemical variability of tailings, and cover the broadest possible range of time scales by experiments. The proposed experimental methodology can be of general use for the design of tailing dam remediation technologies with improvements involving the set of measured variables and sampling frequency and by carefully relating the costs to the institutional aspects of tailing dam management., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Applied research programs in the remediation of contaminated areas can be used also for gaining insights in the physiological and ecological mechanisms supporting the resistance of plant communities in stress conditions due to toxic elements. The research hypothesis of this study was that in the heavily contaminated but nutrient-poor substrate of mine tailing dams, the beneficial effect of inoculation with arbuscular mychorrizal fungi (AMF) is due to an improvement of phosphorus nutrition rather than to a reduction of toxic element transfer to plants. A concept model assuming a causal chain from root colonization to element uptake, oxidative stress variables, and overall plant development was used. The methodological novelty lies in coupling in a single research program experiments conducted at three scales: pot, lysimeter, and field plot, with different ages of plants at the sampling moment (six subsets of samples in all). The inoculation with AMF in expanded clay carrier had a beneficial effect on the development of plants in the amended tailing substrate heavily contaminated with toxic elements. The effect of inoculation was stronger when the quantity of expanded carrier was smaller (1 % vs. 7 % inoculum), probably because of changes in substrate features. The improvement of plant growth was due mainly to an improvement in phosphorus nutrition leading to an increase of protein concentration and decrease of oxidative stress enzyme activity (superoxide dismutase and peroxidase). In a single data subset, an effect of inoculation on the uptake of several toxic elements could be proved (decrease of As concentration in plant roots correlated with a decrease of oxidative stress independent from the effect of P concentration increase). The multi-scale approach allowed us to find differences between the patterns characterising the data subsets. These subset-specific patterns point out the existence of physiological differences between plants in different development states (as a result of sampling at different plant ages). From an applied perspective, conclusions are drawn with respect to the use of plants in the monitoring programs of contaminated areas and the use of inoculation with AMF in the remediation of tailing dams.