Functional traits predict resident plant response to Reynoutria japonica invasion in riparian and fallow communities in southern Poland.

Reynoutria japonica is one of the most harmful invasive species in the world, dramatically reducing the diversity of resident vegetation. To mitigate the impact of R. japonica on ecosystems and properly manage affected areas, understanding the mechanisms behind this plant's invasive success is imperative. This study aimed to comprehensively analyse plant communities invaded by R. japonica, taking into account species traits, habitat conditions and seasonal variability, and to determine the ecological profile of species that withstand the invader's pressure. The study was performed in fallow and riparian areas in southern Poland. Pairs of adjacent plots were established at 25 sites with no obvious signs of recent human disturbance. One plot contained R. japonica, and the other contained only resident vegetation. For each plot, botanical data were collected and soil physicochemical properties were determined. Twelve sites were surveyed four times, in two springs and two summers, to capture seasonal variability. The presence of R. japonica was strongly associated with reduced resident plant species diversity and/or abundance. In addition to the ability to quickly grow and form a dense canopy that shades the ground, the success of the invader likely resulted from the production of large amounts of hard-to-decompose litter. The indirect impact of R. japonica by controlling the availability of nutrients in the soil might also play a role. A few species coexisted with R. japonica. They can be classified into three groups: (i) spring ephemerals - geophytic forbs with a mixed life history strategy, (ii) lianas with a competitive strategy and (iii) hemicryptophytic forbs with a competitive strategy. Species from the first two groups likely avoided competition for light by temporal or spatial niche separation (they grew earlier than or above the invasive plant), whereas the high competitive abilities of species from the third group likely enabled them to survive in R. japonica patches.

Invasive plant Reynoutria japonica produces large amounts of phenolic compounds and reduces the biomass but not activity of soil microbial communities.

Reynoutria japonica is one of the most invasive plant species. Its success in new habitats may be associated with the release of secondary metabolites. The aim of this study was to compare phenolic concentrations in plant biomass and soils between plots with R. japonica and resident plants (control), and determine the effects of these compounds on soil microbial communities. Samples of plant shoots and rhizomes/roots, and soil were collected from 25 paired plots in fallow and riparian habitats in Poland. We measured concentrations of total phenolics, condensed tannins, catechin, chlorogenic acid, emodin, epicatechin, hyperoside, physcion, piceatannol, polydatin, procyanidin B3, quercetin, resveratrol, and resveratroloside. Soil microbial parameters were represented by acid and alkaline phosphomonoesterases, ß-glucosidase, phenoloxidase, and peroxidase activity, culturable bacteria activity and functional diversity measured with Biolog Ecoplates, and microbial biomass and community structure measured with phospholipid fatty acid (PLFA) analysis. We found that concentrations of total phenolics and condensed tannins were very high in R. japonica leaves and rhizomes/roots, and concentrations of most phenolic compounds were very high in R. japonica rhizomes/roots when compared to resident plant species. Concentrations of most phenolics in mineral soil did not differ between R. japonica and control plots; the only exceptions were catechin and resveratrol which were higher and lower, respectively, under the invader. Total microbial and bacterial (G+, G-) biomass was decreased by approx. 30% and fungal biomass by approx. 25% in invaded soils in comparison to control. Among soil functional microbial parameters, only peroxidase activity and functional diversity differed between R. japonica and resident plant plots; peroxidase activity was higher, while functional diversity was lower in soil under R. japonica. The negative effects of R. japonica on microbial biomass may be related to catechin or its polymers (proanthocyanidins) or to other phenolics contained in high concentrations in R. japonica rhizomes.

Soil organic matter prevails over heavy metal pollution and vegetation as a factor shaping soil microbial communities at historical Zn-Pb mining sites.

This study examined the effects of soil heavy metals, macronutrients, texture and pH as well as plant species richness and composition on soil respiration, enzymatic activity, microbial biomass, metabolic quotient (qCO2) and arbuscular mycorrhizal fungi (AMF) at sites of historical Zn-Pb mining. The study was conducted both on a large scale (65 heaps scattered over the area of 750 km2) and on a small scale (25 plots along two 48 m transects extending from heaps to adjacent fallow fields). Total concentrations of metals exceeded 400 (Cd), 20,000 (Pb) and 80,000 (Zn) mg kg-1 at the most polluted sites. Although they decreased along the heap-fallow direction, they still remained above environmental standards in fallow soils. In contrast, some soluble metal forms increased with the increasing distance from heaps. Soil organic matter had the strongest positive effect on most microbial parameters. Total and/or available heavy metals exhibited significant negative effects on microbial biomass, enzymatic activity and AMF, and a positive effect on qCO2. Organic matter alleviated negative effects of heavy metals on microorganisms; they were not observed where the increase in the contamination was accompanied by the increase in organic matter content. Plant species richness affected positively enzymatic activity and mycorrhization level. Plant species composition possibly contributed to the formation of soil microbial communities, but its effect was entangled in that of heavy metals as plant communities changed along pollution gradients (from metal-tolerant grasslands dominated by Festuca ovina to calcareous grasslands and ruderal communities at less polluted sites).

Invasion of Rosa rugosa induced changes in soil nutrients and microbial communities of coastal sand dunes.

The aim of this study was to investigate the influence of R. rugosa invasion on soil physicochemical and microbial properties of coastal sand dunes. The study was performed at 25 paired invaded-native plots along the Hel Peninsula at the coast of the Baltic Sea. A number of soil physicochemical and microbial parameters were measured, namely organic matter layer thickness, pH, electrical conductivity, organic C, total Ca, N, Na, P, N-NH4, N-NO3 and P-PO4 concentrations, phospholipid and neutral fatty acid (PLFA, NLFA) markers of total microbial, bacterial, fungal biomass and microbial community structure, as well as arbuscular mycorrhizal fungi (AMF) spore and species numbers, and the degree of AMF root colonization. Since potential alterations in soil parameters induced by R. rugosa may be related to large amounts of secondary metabolites provided to the soil with litter or root exudates, total phenolic concentration in senescing tissues of R. rugosa and native species was compared. Rosa rugosa invasion was associated with increased organic C, total N and P-PO4 concentrations in mineral soil relative to native vegetation. Organic matter layer under R. rugosa was thicker, had higher pH and Ca concentration. Rosa rugosa invasion was associated with reduced total microbial, bacterial and G+ bacterial biomass and increased AMF biomass markers (16:1ω5 NLFA and 16:1ω5 NLFA/PLFA), and changes in microbial community structure in mineral soil. The reduction in total and bacterial biomass under R. rugosa might have been related to the production of secondary metabolites as total phenolic concentration was approx. 5 times higher in senescing tissues of R. rugosa than in native vegetation. The observed increase in element concentrations and alterations in microbial community structure suggest that invasion of R. rugosa may threaten nutrient-poor habitats of coastal dunes. Changes in the soil environment may hinder restoration of these valuable habitats after invader removal.

Relationships between waste physicochemical properties, microbial activity and vegetation at coal ash and sludge disposal sites.

The aim of the study was to assess the relationships between vegetation, physicochemical and microbial properties of substrate at coal ash and sludge disposal sites. The study was performed on 32 plots classified into 7 categories: dried ash sedimentation ponds, dominated by a grass Calamagrostis epigejos (AH-Ce), with the admixture of Pinus sylvestris (AH-CePs) or Robinia pseudoacacia (AH-CeRp), dry ash landfill dominated by Betula pendula and Pinus sylvestris (AD-BpPs) or Salix viminalis (AD-Sv) and coal sludge pond with drier parts dominated by Tussilago farfara (CS-Tf) and the wetter ones by Cyperus flavescens (CS-Cf). Ash sites were covered with soil layer imported as a part of technical reclamation. Ash had relatively high concentrations of some alkali and alkaline earth metals, Mn and pH, while coal sludge had high water and C, S, P and K contents. Concentrations of heavy metals were lower than allowable limits in all substrate types. Microbial biomass and, particularly, enzymatic activity in ash and sludge were generally low. The only exception were CS-Tf plots characterized by the highest microbial biomass, presumably due to large deposits of organic matter that became available for aerobic microbial biomass when water level fell. The properties of ash and sludge adversely affected microbial biomass and enzymatic activity as indicated by significant negative correlations between the content of alkali/alkaline earth metals, heavy metals, and macronutrients with enzymatic activity and/or microbial biomass, as well as positive correlations of these parameters with metabolic quotient (qCO2). Plant species richness and cover were relatively high, which may be partly associated with alleviating influence of soil covering the ash. The effect of the admixture of R. pseudoacacia or P. sylvestris to stands dominated by C. epigejos was smaller than expected. The former species increased NNH4, NNO3 and arylsulfatase activity, while the latter reduced activity of the enzyme.

Waste heaps left by historical Zn-Pb ore mining are hotspots of species diversity of beech forest understory vegetation.

Metalliferous mining and smelting industries are associated with very high levels of heavy metal(loid) contamination of the environment. Heavy metals have been proved to significantly influence the species diversity and composition of grassland communities, but little is known on their effects on forest understory vegetation. Therefore, the aim of this study was to investigate the effects of the presence of small heaps of waste rock left by historical Zn-Pb ore mining on understory vegetation. The heaps are scattered over vast areas of beech forests in southern Poland. Three types of study plots were established: (1) on waste heaps themselves, (2) in their vicinity (5-10m from the foot of the heaps, with no waste rock but potentially influenced by the heaps through drainage water), and (3) at least 100m from the foot of the heaps (pseudo-control). In all plots vegetation parameters, i.e., plant species number, cover and community composition, life forms and strategies, as well as basic soil properties were assessed. Although the heaps contained high concentrations of metals, namely Cd, Pb and Zn, they were characterised by higher cover and diversity of understory vegetation, including ancient forest and endangered species, in comparison to their surroundings. They were also characterised by the distinct species composition of their plant communities. This might have resulted from the beneficial influence of high pH and Ca content originating from waste rock composed of dolomite and calcite, as well as from increased habitat heterogeneity, e.g. soil skeleton and steeper slopes. Another important factor influencing the richness and composition of understory was tree cover, which relates to the light transmissibility of the canopy. Our study proved that the disturbance brought about by the former mining and processing of metal ores led to the formation of species-rich understory with high frequency and cover of naturally-valuable species.

Variation in dry grassland communities along a heavy metals gradient.

The aim of this study was to investigate the variation in plant communities growing on metal-enriched sites created by historical Zn­Pb mining. The study sites were 65 small heaps of waste rock covered by grassland vegetation and scattered mostly over agricultural land of southern Poland. The sites were described in terms of plant coverage, species richness and composition, and the composition of plant traits. They were classified using phytosociological methods and detrended correspondence analysis. Identified plant communities were compared for vegetation parameters and habitat properties (soil characteristics, distance from the forest) by analysis of variance. The variation in plant community parameters was explained by multiple regression, in which the predictors were properties of the habitat selected on the basis of factor analysis. Grasslands that developed at low and high concentrations of heavy metals in soil were similar to some extent: they were composed on average of 17­20 species (per 4 m(2)), and their total coverage exceeded 90%. The species composition changed substantially with increasing contamination with heavy metals; metal-sensitive species withdrew, while the metal-tolerant became more abundant. Other important predictors of community structure were: proximity to the forest (responsible for the encroachment of competitive forest species and ruderals), and the thickness of the surface soil (shallow soil favored the formation of the heavy metal grassland). The heavy metal grassland was closely related to the dry calcareous grasslands. The former was an earlier succession stage of the latter at low contamination with heavy metals.

The accumulation of elements in plants growing spontaneously on small heaps left by the historical Zn-Pb ore mining.

The study evaluated the levels of nine metals, namely Ca, Cd, Fe, K, Mg, Mn, Pb, Tl, and Zn, in soils and tissues of ten plant species growing spontaneously on heaps left by historical mining for Zn-Pb ores. The concentrations of Cd, Pb, Tl, and Zn in heap soils were much higher than in control soils. Plants growing on heaps accumulated excessive amounts of these elements in tissues, on average 1.3-52 mg Cd kg(-1), 9.4-254 mg Pb kg(-1), 0.06-23 mg Tl kg(-1) and 134-1479 mg Zn kg(-1) in comparison to 0.5-1.1 mg Cd kg(-1), 2.1-11 mg Pb kg(-1), 0.02-0.06 mg Tl kg(-1), and 23-124 mg Zn kg(-1) in control plants. The highest concentrations of Cd, Pb, and Zn were found in the roots of Euphorbia cyparissias, Fragaria vesca, and Potentilla arenaria, and Tl in Plantago lanceolata. Many species growing on heaps were enriched in K and Mg, and depleted in Ca, Fe, and Mn. The concentrations of all elements in plant tissues were dependent on species, organ (root vs. shoot), and species-organ interactions. Average concentrations of Ca, K, and Mg were generally higher in shoots than in roots or similar in the two organs, whereas Cd, Fe, Pb, Tl, and Zn were accumulated predominantly in the roots. Our results imply that heaps left by historical mining for Zn-Pb ores may pose a potential threat to the environment and human health.

Monomorphic ants undergo within-colony morphological changes along the metal-pollution gradient.

In ants, intra and inter-colony variation in body size can be considerable, even in monomorphic species. It has been previously shown that size-related parameters can be environmentally sensitive. The shape of the body size distribution curve is, however, rarely investigated. In this study, we measured head widthes of the black garden ant Lasius niger workers using digital methods. The ants were sampled from 51 colonies originating from 19 sites located along a metal pollution gradient, established in a former mining area in Poland. Total zinc concentrations in random samples of small invertebrates were used as a measure of site pollution levels. We found that the skewness of head size distribution grows significantly in line with the pollution level of the site, ranging from values slightly below zero (about -0.5) in the least polluted site up to a positive value (about 1.5) in the most polluted site. This result indicates that the frequency of small ants grows as pollution levels increase. The coefficient of variation, as well as the measures of central tendency, was not related to the pollution level. Four hypotheses explaining the obtained results are proposed. The bias towards the higher frequency of small workers may result from energy limitation and/or metal toxicity, but may also have an adaptive function.