Ilona Mészáros

Biodiversity Differences between Managed and Unmanaged Forests: Meta-Analysis of Species Richness in Europe

Past and present pressures on forest resources have led to a drastic decrease in the surface area of unmanaged forests in Europe. Changes in forest structure, composition, and dynamics inevitably lead to changes in the biodiversity of forest-dwelling species. The possible biodiversity gains and losses due to forest management (i.e., anthropogenic pressures related to direct forest resource use), however, have never been assessed at a pan-European scale. We used meta-analysis to review 49 published papers containing 120 individual comparisons of species richness between unmanaged and managed forests throughout Europe. We explored the response of different taxonomic groups and the variability of their response with respect to time since abandonment and intensity of forest management. Species richness was slightly higher in unmanaged than in managed forests. Species dependent on forest cover continuity, deadwood, and large trees (bryophytes, lichens, fungi, saproxylic beetles) and carabids were negatively affected by forest management. In contrast, vascular plant species were favored. The response for birds was heterogeneous and probably depended more on factors such as landscape patterns. The global difference in species richness between unmanaged and managed forests increased with time since abandonment and indicated a gradual recovery of biodiversity. Clearcut forests in which the composition of tree species changed had the strongest effect on species richness, but the effects of different types of management on taxa could not be assessed in a robust way because of low numbers of replications in the management-intensity classes. Our results show that some taxa are more affected by forestry than others, but there is a need for research into poorly studied species groups in Europe and in particular locations. Our meta-analysis supports the need for a coordinated European research network to study and monitor the biodiversity of different taxa in managed and unmanaged forests.

Effects of the available nitrogen on the photosynthetic activity and xanthophyll cycle pool of maize in field

Summary Investigations were performed on the interrelation between the photoprotective role of the xanthophyll cycle and levels of N-supply in maize plants ( Zea mays L. cv. Maya). Plants were grown in non-fertilised and fertilised plots, while the latter were supplied with 30, 60, 90, 120 and 150 kg ha −1 NH 4 NO 3 and grown under natural conditions in the field. The photosynthetic carbon assimilation of plants with higher N-supply, as compared to that of plants with lower N-supply, showed no significant differences, although a peak of the CO 2 assimilation rate was observed at 60 and 90 kg N ha −1 treatment levels. Maize plants with lower N-supply had a lower leaf Chl-content than plants with higher N-supply, which was accompanied by a reduced rate of photochemical efficiency of photosystem II and a high thermal energy dissipation activity, measured as non-photochemical fluorescence quenching. Plants supplied with lower doses of N were detected to have a greater fraction of xanthophyll cycle pool in the form zeaxanthin and antheraxanthin. With reduction of the N-supply levels an increase in the ratio of xanthophyll cycle pigments as related to total Chl was observed. These results suggest that with the decrease of N-supply there is an increasing need to dissipate the excess light energy in the chloroplasts of maize leaves through xanthophyll cycle.

Effect of chromium on photosystem 2 in the unicellular green alga, Chlorella pyrenoidosa

We investigated the effect of chromium (20–40 g m−3, 8–72 h) on the photosystem 2 (PS2) activities of Chlorella pyrenoidosa cells. By using chlorophyll fluorescence transients, thermoluminescence, oxygen polarography, and Western blot analysis for D1 protein we found that inhibition of PS2 can be accounted for by the enhanced photodestruction of the reaction centres in the cells cultivated in the presence of Cr(VI) at 25 °C in “white light” (18 W m−2). Hence photodestruction of D1 is caused by an enhanced oxidative stress and lipid peroxidation, as indicated by the appearance of a high-temperature thermoluminescence band.

Heavy metal content of common reed (Phragmites australis/Cav./Trin, ex Steudel) and its periphyton in Hungarian shallow standing waters

In order to reveal the actual effects of common reed (Phragmites australis (Cav) Trin. ex Steudel) and its periphyton complex on the water quality, studies on the heavy metal contents of common reed and its periphyton are important. This paper discusses the results of studies on heavy metal contents of the host plant-periphyton complex carried out in Lake Balaton, Lake Velence, Lake Fertö and Kis-Balaton Reservoir. A second goal was to study the effects of reed stands in different condition (healthy, transitional, die-back) on the structure of its periphyton and their role in water quality indication. Simultaneously with the reed and periphyton sampling, water samples were taken for investigation. We determined the wet mass of periphyton and after drying at 105 °C; the dry mass was measured and ash contents of reed and its periphyton samples were also determined. The concentration of 27 (Na, Mg, Ca, K, Zn, Cu, Cd, Cr, Pb, Mo, etc.) cations was determined from the reed, periphyton and water samples by ICP-AES method. The heavy metal content of reed and periphyton was especially high at places impacted by high anthropogenic loadings. On the basis of our results, the biofilter role of periphyton-reed complex can be confirmed. Since the main reasons of reed decline have not been revealed, future research has to focus on involving reed-periphyton studies also, which may provide good basis to find the most appropriate ways to protect and restore the reed communities of shallow standing waters.

Ecotoxicological studies and risk assessment on the cyanide contamination in Tisza river

As a result of the dam failure of January 30, 2000 in Rumania, water and a huge amount of sediment contaminated with cyanide and later heavy metals entered the Tisza river system. In order to determine the chronic consequences of the contamination, periphyton and sediment samples were collected from River Tisza and her tributaries over the next 2 years. After flooding periods, the sediment deposited in the foreshore was also sampled. Applying the ICP-AES analysis method, the amounts of major heavy metals in the periphyton and sediment samples were measured, and the related concentration factors were calculated. Attempts were also made to find a correlation with the toxicity data. Ecotoxicological analyses were performed on the sediment using the following test techniques: Daphnia test, static fish test, alga test (chlorophyll content measurements), seedling test (Sinapis) and Lemna test (increase in mass and measurements on the chlorophyll concentration). Examinations on the chronic effects of heavy metals deposited in the periphyton and sediment can be regarded as an important factor in assessing ecological-conservational disasters and in carrying out biomonitoring activities in the future.

Application of Lemna species in ecotoxicological studies of heavy metals and organic biocides

Abstract Owing to their small size and easy manipulation under aseptic conditions, duckweeds (Lemnaceae) provide good material for studying the effects of toxicants and organic biocides. Applying static acute ecotoxicological tests the responses of three duckweed species to different chemicals were compared. In each species the IC 50 values of copper and Bonion biocide reached 10 mg/1 and 15 mg/1, respectively. Comparing the two Lemna species L. minor proved to be more sensitive than L. gibba . Simultaneously with the measurement of the productivity the changes in the CO 2 and O 2 exchange were also determined during the static acute tests of biocide (methylene bisthiocyanate) by means of a gas analyser (Quadrupole MS) in special growth chambers. There were no correlations between the respiration of duckweds and the concentration of biocide. Differences were found in the intensity of the photosynthesis as a function of the biocide treatment.

Short-term chromium(VI) stress induces different photosynthetic responses in two duckweed species, Lemna gibba L. and Lemna minor L.

Physiological responses of two duckweed species, Lemna gibba and Lemna minor, to hexavalent chromium [Cr(VI)] were studied in axenic cultures using short-term (48 h) treatments by K2Cr2O7 (0–200 μM). Chlorophyll (Chl) fluorescence parameters and photosynthetic pigment composition of plants were screened to determine the effects of Cr(VI) exposures. The two duckweed species exhibited different sensitivity in the applied Cr(VI) concentration range. Chl fluorescence parameters of dark-adapted and light-adapted plants and electron transport inducibility were more sensitive to Cr(VI) in L. minor than in L. gibba. We also found fundamental differences in quantum yield of regulated, Y(NPQ), and nonregulated, Y(NO), non-photochemical quenching between the two species. As Cr(VI) concentration increased in the growth medium, L. minor responded with considerable increase of Y(NPQ) with a parallel significant increase of Y(NO). By contrast, in L. gibba only 200 μM Cr(VI) in the growth medium resulted in elevation of Y(NPQ) while Y(NO) remained more or less constant within the regarding Cr(VI) concentration range during 48 h. Photosynthetic pigment content did not change considerably during the short-term Cr(VI) treatment but decrease of Chl a/b and increase of Car/Chl ratios were observed in good accordance with the changes in Chl fluorescence parameters. The data suggest that various duckweed species respond with different sensitivity to the same ambient concentrations of Cr(VI) in the growth medium, and presumably to other environmental stresses too, which may have an influence on their competitive relations when heavy metal pollution occurs in aquatic ecosystem.

Cylindrospermopsin and microcystin-LR alter the growth, development and peroxidase enzyme activity of white mustard (Sinapis alba L.) seedlings, a comparative analysis

This work focuses on the comparative analysis of the effects of two cyanobacterial toxins of different chemical structure cylindrospermopsin (CYN) and microcystin-LR (MC-LR) on the white mustard (Sinapis alba L.) seedlings. Both cyanotoxins reduced significantly the fresh mass and the length of cotyledons, hypocotyls and main roots of seedlings in a concentration dependent manner. For various mustard organs the 50% inhibitory concentration values (IC50) of growth were between 3-5 μg ml(-1) for MC-LR and between 5-10 μg ml-1 for CYN, respectively. Cyanotoxins altered the development of cotyledons, the accumulation of photosynthetically active pigments and anthocyanins. Low MC-LR concentrations (0.01 and 0.1 μg ml(-1)) stimulated anthocyanin formation in the cotyledons but higher than 1 μg ml(-1) MC-LR concentrations strongly inhibited it. The CYN treated chlorotic cotyledons were violet coloured in consequence of high level of anthocyanins, while MC-LR induced chlorosis was accompanied by the appearance of necrotic patches. Necrosis and increases of peroxidase enzyme activity (POD) are general stress responses but these alterations were characteristic only for MC-LR treated mustard plants. These findings provide experimental evidences of developmental alterations induced by protein synthesis and protein phosphatase inhibitory cyanotoxins (CYN and MC-LR) in a model dicotyledonous plant.

Carotenoid composition and photochemical activity of four sandy grassland species

The photosynthetic pigments and photochemical efficiency of photosystem 2 (PS2) were studied in four constitutive species (Achillea millefolium L., Festuca pseudovina Hack. ex Wiesb., Potentilla arenaria Borkh., and Thymus degenianus Lyka) of a semiarid grassland in South-eastern Hungary. Every species displayed typical sun-adapted traits and substantial plasticity in the composition and functioning of the photosynthetic apparatus. The contents of chlorophylls (Chls) and carotenoids (Cars) on a dry matter basis declined from May to July, however, the amount of total Cars on a Chl basis increased. This increase was the largest in Potentilla (48 %) and the smallest in Achillea (14 %). The pool of xanthophylls (VAZ) was between 25 % and 45 % of the total Car content and was larger in July than in May. The content of β-carotene increased by July, but lutein content did not change significantly. The Chl fluorescence ratio Fv/Fm was reduced by 3–10 % at noon, reflecting the down-regulation of PS2 in the period of high irradiance and high temperature. The occurrence of minimal values of ΔF/Fm’ showed close correlation to the de-epoxidation rate of violaxanthin. Hence in natural habitats these species developed a considerable capacity to dissipate excess excitation energy in the summer period in their photosynthetic apparatus through the xanthophyll cycle pool and a related photoprotective mechanism, when the photochemical utilization of photon energy was down-regulated.

Variations in leaf pigment content and photosynthetic activity of Phragmites australis in healthy and die-back reed stands of Lake Ferto/Neusiedlersee

The photosynthetic capacity of the common reed (Phragmites australis /Cav./ Trin. ex Steudel) was studied in various reed stands in the littoral zone of Lake Fertõ. Measurements were performed in three healthy and two dieback reed stands in the summer of 1997. In the leaves of declining reeds, the chlorophyll content was lower than in the vigorous sites. In the former sites, there was a significant rise in the total carotenoid pool (320–480 mmol mol−1chl (a + b)) as compared to that of the vigorous sites (250–350 mmol mol−1 chi (a + b). The size of the xanthophyll cycle pool and the β-carotene content of leaves significantly increased in the die-back sites. In early summer, the potential photochemical quantum efficiency of Photosystem II (Fv/Fm) did not differ considerably (0.79–0.81) from site to site, yet by August it significantly decreased (0.74–0.77) in the die-back sites as compared to the vigorous sites. The maximum CO2 assimilation rate measured on the 3rd and 4th leaves ranged from 11 to 17 CO2μmol m−2 s−1 and from 9 to 12 CO2μmol m−2 s−1 in the vigorous sites and the die-back sites, respectively. The stomatal conductance was also lower in the die-back sites (200–350 mmol H2O m−2 s−1) than in the vigorous reed stands (380–510 mmol H2O m−2s−1) which might result in the functional impairment of the gas ventilation system of the declining reeds, and consequently in oxygen deficiency and damage to the rhizome.