Can Environmental Stressors Determine the Condition of Ecological Plant Groups?

There is still a need to investigate the relationships between glycophytes and halophytes and the many biotic and abiotic factors in their natural environments. Therefore, we study the effects of the type of environment on the ecophysiological responses and condition of the glycophyte Elder Sambucus nigra L., the macrophyte Common Reed Phragmites australis (Cav.) Trin. ex Steud., the facultative halophyte Weeping Alkaligrass Puccinellia distans (Jacq.) Parl, and the obligate halophyte Common Glasswort Salicornia europaea L. in a saline-disturbed anthropogenic region of central Poland. We analyzed the effects of salinity, acidity, and soil organic matter on shoot length, lipoperoxidation, and proline in roots and green parts, and evaluated plant responses to environmental disturbance, which allowed for the comparison of adaptation strategies. The studies were carried out in (1) "sodium production" (near sodium factories), (2) "anthropogenic environments" (waste dumps, agroecosystems, calcium deposits, post-production tanks), (3) "wetland environments" (near river channels and riparian areas), and (4) "control" (natural, unpolluted environments). Green parts of plants are better suited to indicate environmental stress than roots. Their higher structural MDA membrane damage is related to the transport of toxic ions to the shoots by a rapid transpiration stream in the xylem. We found high salinity to be the main factor inducing growth and found it to be correlated with the high pH effect on proline increase in glycophytes (Elder, Reed) and Weeping Alkaligrass, in contrast to Common Glasswort. We suggest that proline accumulation allows osmotic adjustment in the green parts of reeds and alkaligrasses, but may have another function (in Elder). Common Glasswort accumulates large amounts of Na+, which is energetically more effective than proline accumulation for osmotic adjustment. Organic matter affects plant growth and proline levels, but soil salinity and pH alter nutrient availability. Plant distribution along the salinity gradient indicates that Elder is the most salt-sensitive species compared to Reed, Alkaligrass, and Glasswort. Salinity and the lack of control of thick reeds, which compete with other plant groups, affect the distribution of halophytes in saline environments.

Growth Stage-, Organ- and Time-Dependent Salt Tolerance of Halophyte Tripolium pannonicum (Jacq.) Dobrocz

Tripolium pannonicum (Jacq.) Dobrocz. is a member of the diverse group of halophytes with the potential for the desalination and reclamation of degraded land. The adaptive processes of T. pannonicum to salinity habitats are still not well recognized. Therefore, we evaluated the effect of NaCl (0, 200, 400, and 800 mM) on: (1) two plant growth stages, (2) the activity of antioxidant enzymes and concentration of H₂O₂ and the proline in roots, stems, and leaves, and (3) the effect of long- and short-term salt stress on physiological responses. Germination, pot experiments, and a biochemical analysis were performed. The effective T. pannonicum's seed germination was achieved in the control. We demonstrated that halophyte's organs do not simply tolerate high-salt conditions. The activities of APX, POD, and catalase observed at 400 mM and 800 mM NaCl were varied between organs and revealed the following pattern: root > leaves > stem. Proline was preferentially accumulated in leaves that were more salt-tolerant than other organs. Salt stress enhanced the activity of antioxidant enzymes and concentrations of salinity stress indicators in a time-dependent manner. Our study has indicated that salt tolerance is a complex mechanism that depends on the growth phase, organs, and duration of salinity exposure. The results have potential for further proteomic and metabolomic analyses of adaptive salt tolerance processes.

Vegetation of temperate inland salt-marshes reflects local environmental conditions

Inland salt marshes are recognized as habitats of unique and valuable vegetation at the European scale. There is still a lack of generalization regarding its vegetation syntaxonomy and environmental requirements, which is needed for its effective protection. To falsify our hypothesis about vegetation dependence on environmental requirements we aimed at description of the syntaxonomical units present in temperate European inland salt marshes and identification of their main environmental drivers. In our work we focused on the vegetation from the northern part of temperate salt marshes to limit confusion related to the geographical ranges of species. We collected the database of 968 vegetation plots from different European countries and applied the Cocktail method to analyze the data. Based on results, expert knowledge, existing syntaxonomical classifications and information from the literature, we identified diagnostic, constant and dominant species for individual syntaxonomical units. Then, we compiled maps of the vegetation unit distribution, and identified the most important environmental factors for the analyzed vegetation using statistical and multivariate methods, including canonical variate analysis. We classified the analyzed vegetation into nine classes, including two typical for salt-marsh vegetation - the Therosalicornietea and Festuco-Puccinellietea. Within these two classes, we distinguished two alliances and a total of five associations. The classes differ the most in terms of species preferences to salinity, soil moisture, light availability and soil nitrogen content. In addition salt marsh associations differ also by soil reaction and soil organic matter content. This provides direct implications for salt marsh sustainable management.

Current Condition of Pannonic Salt Steppes at Their Distribution Limit: What Do Indicator Species Reveal about Habitat Quality?

Little is known about the suite of ecological conditions under which characteristic species may continue to develop under the pressure of recent habitat deterioration. We aimed to determine the niche of three indicator species of the priority habitat Pannonic salt steppes and to find out how their vegetation composition, land use, and soil chemistry mirror the current condition of their typical habitat. A plot-based vegetation survey was conducted in degraded and in pristine (reference) inland salt steppes in East-Central Europe. We confirmed decreased habitat quality at their northern geographical limit. Most of the sites there showed a strong prevalence of generalists (e.g., Elytrigia repens) and lack of specialists, both resulting from lowered habitat extremity and inappropriate land use (abandonment). A small proportion of plots (19%) were in the same good condition as the reference vegetation in the central area. Soil analyses revealed that the studied halophytes are able to persist on desalinized soils if the land use is suitable. The occurrence of the annual Camphorosma annua (Amaranthaceae) was driven largely by abiotic stress; grazing alone is insufficient for its long-term persistence, while the perennial Artemisia santonicum (Asteraceae) and Tripolium pannonicum (Asteraceae) have higher survival chances as they are able to coexist with generalists. Overall habitat quality can be reliably determined from the analyzed ecological conditions of indicator species. The outcomes of the presented work are relevant for conservation practice and can serve as a quick tool for assessing the current stage of other grassland habitats.

Antioxidant defence barrier of great tit Parus major nestlings in response to trace elements

Metals can have direct and indirect effects on the generation of reactive oxygen species in wild birds. The aim of this work has been to examine the effect of exposure to trace metals (copper Cu, iron Fe, cobalt Co, manganese Mn) on oxidative stress biomarkers such as lipoperoxidation TBARS and level of superoxide dismutase SOD, catalase CAT, and reduced glutathione GSH in the livers and kidneys of great tit Parus major nestlings (n = 165, 63 broods) living in polluted environments associated with soda plants and agricultural activities (Kujawy region) and from a reference site (Tuchola Forest), both in the north of Poland. As we predicted, the level of TBARS in both organs of chicks from polluted areas was higher than in those from reference site. This could be connected with Fe concentrations, particularly in areas adjacent to soda plants (livers R_s = 0.49, p < 0.002; kidneys R_s = 0.69, p < 0.001). We also showed differences in the level of antioxidants depending on the environment. CAT activity was higher in nestlings from Kujawy than in those from Tuchola. Meanwhile SOD activity (both organs) and GSH levels (kidneys) were lower in the polluted area compared to the reference site. Concentrations of Cu, Fe, Co, and Mn may play a role in regulating the antioxidant system components' activity.

Edaphic characterization and plant zonation in the Qaidam Basin, Tibetan Plateau

This paper presents a study of edaphic characteristics and their relationship with plant distribution in the Qaidam Basin, Tibetan Plateau, and establishes a distribution model for plants in sandy gravel Gobi to dry salt lake areas. All of the communities in the study area were dominated by plants with strong saline-alkaline tolerance. In this area, salts appeared to migrate to the surface; the surface soil was striped, and the salt distribution varied from sandy gravel Gobi to dry salt lake areas. The salt composition mainly consisted of NaCl in the surface crust. In the subsurface layers, the salt composition was dominated by Ca²⁺, Cl^- and SO₄^2-. The type of vegetation at the study site can be divided into two categories: salt-tolerant vegetation and weakly salt-tolerant vegetation. The salt-tolerant vegetation is influenced by Na⁺, Cl^-, and the salinity. The soil of these vegetation communities had a higher salt and Na⁺ concentration and a lower Ca²⁺ and K⁺ concentration. The weakly salt-tolerant vegetation is mainly affected by the Ca²⁺/Na⁺ and K⁺/Na⁺ ratios. Based on the above results, a vegetation distribution model for saline lakes on the inland plateau was established.

The threat of soil salinity: A European scale review

Soil salinisation is one of the major soil degradation threats occurring in Europe. The effects of salinisation can be observed in numerous vital ecological and non-ecological soil functions. Drivers of salinisation can be detected both in the natural and man-made environment, with climate and the foreseen climate change also playing an important role. This review outlines the state of the art concerning drivers and pressures, key indicators as well as monitoring, modeling and mapping methods for soil salinity. Furthermore, an overview of the effect of salinisation on soil functions and the respective mechanism is presented. Finally, the state of salinisation in Europe is presented according to the most recent literature and a synthesis of consistent datasets. We conclude that future research in the field of soil salinisation should be focused on among others carbon dynamics of saline soil, further exploration of remote sensing of soil properties and the harmonization and enrichment of soil salinity maps across Europe within a general context of a soil threat monitoring system to support policies and strategies for the protection of European soils.

Effects of chemical elements in the trophic levels of natural salt marshes

The relationships between the bioaccumulation of Na, K, Ca, Mg, Fe, Zn, Cu, Mn, Co, Cd, and Pb, acidity (pH), salinity (Ec), and organic matter content within trophic levels (water-soil-plants-invertebrates) were studied in saline environments in Poland. Environments included sodium manufactures, wastes utilization areas, dumping grounds, and agriculture cultivation, where disturbed Ca, Mg, and Fe exist and the impact of Cd and Pb is high. We found Zn, Cu, Mn, Co, and Cd accumulation in the leaves of plants and in invertebrates. Our aim was to determine the selectivity exhibited by soil for nutrients and heavy metals and to estimate whether it is important in elucidating how these metals are available for plant/animal uptake in addition to their mobility and stability within soils. We examined four ecological plant groups: trees, shrubs, minor green plants, and water macrophytes. Among invertebrates, we sampled breastplates Malacostraca, small arachnids Arachnida, diplopods Diplopoda, small insects Insecta, and snails Gastropoda. A higher level of chemical elements was found in saline polluted areas (sodium manufactures and anthropogenic sites). Soil acidity and salinity determined the bioaccumulation of free radicals in the trophic levels measured. A pH decrease caused Zn and Cd to increase in sodium manufactures and an increase in Ca, Zn, Cu, Cd, and Pb in the anthropogenic sites. pH increase also caused Na, Mg, and Fe to increase in sodium manufactures and an increase in Na, Fe, Mn, and Co in the anthropogenic sites. There was a significant correlation between these chemical elements and Ec in soils. We found significant relationships between pH and Ec, which were positive in saline areas of sodium manufactures and negative in the anthropogenic and control sites. These dependencies testify that the measurement of the selectivity of cations and their fluctuation in soils provide essential information on the affinity and binding strength in these environments. The chemical elements accumulated in soils and plants; however, further flow is selective and variable. The selectivity exhibited by soil systems for nutrients and heavy metals is important in elucidating how these metals become available for plant/animal uptake and also their mobility and stability in soils.

Effect of experimental top soil removal on vegetation of Pannonian salt steppes

Inland saline habitats of the Pannonian Lowland exhibit a specific variety of grasslands determined by a soil salinity gradient. Changes in the hydrological regime and absence of management have resulted in heavy degradation of the vegetation. The impact of topsoil removal on salt steppes was tested by a 3-year small-scale manipulated experiment in SW Slovakia (Kamenínske Slanisko Nature Reserve). Topsoil was removed in three contrasting types of vegetation with different soil salinities, i.e. in different stages of habitat degradation. Data were analysed by multi-way ANOVA and by multivariate methods. Species richness decreased and the proportion of halophytes increased significantly in the two types with the highest soil salinity; however, the total number of halophytes was not influenced by soil removal. The treatment caused inhibition of secondary succession on the plots with the highest salinity. The effect of the soil removal was only short-term in the vegetation with moderate salinity and on heavily degraded and desalinized types it even stimulated further recruitment of ruderal species. Topsoil removal has only limited potential for the restoration of Pannonian salt steppes. It should be applied only in slightly degraded vegetation, where salt accumulation is still present and target species propagules are available.