Péter Csontos

Early distribution and spread of Ambrosia artemisiifolia in Central and Eastern Europe

The introduction and early spread of common ragweed (Ambrosia artemisiifolia L.) in Central and Eastern Europe were reconstructed based on a study of all herbarium specimens of common ragweed deposited at six herbaria in Austria, Hungary and Serbia. More than 450 specimens were examined and the oldest ones, collected from 1907 to 1927, were used to map the historical spread of this highly allergenic invasive weed in this region. The herbarium records back-date the first known introduction of this noxious weed to Central and Eastern Europe as well as its early spread on the Danube-Tisza Plain, and in the North-Eastern part of Hungary. The data also confirm that the introduction of common ragweed to Central and Eastern Europe took place later than its introduction to the Western part of the continent.

Comparisons of soil seed bank classification systems

Since 1969, ten soil seed bank classification systems have been published. Among these systems, the number of recognized seed bank categories varies from three to twelve. Seed longevity is the main factor used for distinguishing categories, but dormancy and germination types are also important. Systems considering relatively few seed bank categories have been the most commonly proposed in contemporary plant ecology. In contrast, systems involving high numbers of categories have received limited interest because the detailed ecological knowledge of individual species required for their successful categorization is usually missing. A comprehensive table on the main features of seed bank classification systems is provided.

Occurrence and ecological characteristics of C4 dicot and Cyperaceae species in the Hungarian flora

AbstractThe non-graminaceous wild flora of Hungary was screened for C4 plants by using the stable carbon isotope ratio, the leaf anatomy and the photosynthetic carbon dioxide compensation concentration to determine the photosynthetic pathway type. On the whole, 31 C4 species (native or naturalized) were found in the Amaranthaceae, Chenopodiaceae, Cyperaceae, Euphorbiaceae, Portulacaceae and Zygophyllaceae families. Together with the 26 C4 grass species (Poaceae) reported earlier (Kalapos 1991), a total of 57 wild C4 species occur in Hungary, which forms 2.6 % of the countrys angiosperm flora. This figure is somewhat higher than what was expected on climatic grounds, a fact probably due to certain edaphic conditions favouring C4 plant growth. In Hungary, the C4 species are predominantly annuals growing in open habitats such as dry grasslands, inland saline areas, temporarily exposed riverbeds and disturbed sites. In comparison with C3 plants, the C4 species have higher temperature and light preferences, and their phenology lags behind that of the C3 plants. These differences might account for C4 plants being usually excluded from productive biotopes in Hungary, where the C3 canopy may become closed during the growing season before C4 plants can start their ontogenetic development. Ecological properties of C3 and C4 plants differ considerably in the Cyperaceae, but much less in the Chenopodianceae family. Among C4 annuals naturalized aliens are common, most of which colonized hungary in the last two centuries. Increasing preponderance of C4 plants is anticipated in the future as a consequence of possible climate changes and the ever increasing human impact on terrestrial vegetation.

An extension of presence/absence coefficients to abundance data: a new look at absence

. Alternative community analyses, based on quantitative and presence/absence data, are comparable logically if the data type is the only factor responsible for differences among results. For presence/absence indices that consider mutual absences, no quantitative alternatives are known. To facilitate such comparisons, a new family of similarity coefficients is proposed for abundance data. Formally, this extension is achieved by generalizing the four cells of the usual 2 × 2 contingency table to the quantitative case. This implies an expanded meaning of absence: for a given species at a given site it is understood as the difference between the actual value and the maximum detected in the entire study. The correspondence between 10 presence/absence coefficients and their quantitative counterparts is evaluated by graphical comparisons based on artificial data. The behaviour of the new functions is also examined using field data representing post-fire regeneration processes in grasslands and a chronosequence pertaining to forest regeneration after clear-cut. The examples suggest that the new coefficients are most informative for data sets with low beta-diversity and temporal background changes.

The applicability of a seed ecological database (SEED) in botanical research

This is the first report on the SEed Ecological Database (SEED) being developed under the co-ordination of the author. In its first version the database will cover physical characteristics of seeds, such as: slenderness (length/width), flatness (thickness/width) and thousand-seed weight. The list of species encompasses all seed plants (gymnosperms and angiosperms) native or naturalized in Hungary (about 2450 species). Two examples to demonstrate the power of SEED are included. The significantly lower slenderness values of Hungarian C4 grasses (compared with C3 types), shown in the first example, is a new contribution to understanding the ecology of C4 grasses. In the second example heavier seed weights of shade plants are statistically demonstrated, compared to their heliophilous congeners with the same life forms. The 113 congeneric species pairs considered are derived from a wide range of plant families.

Slope aspect affects the seed mass spectrum of grassland vegetation

Seed mass distribution in grassland communities of slopes of contrasting aspect was analysed in dolomite regions of the Pannonian Basin. Species frequencies were obtained for four pairs of data sets, which originated from corresponding south- and north-facing dolomite grasslands, thus forming four independent case studies. The data sets comprised 5–15 sample plots and 51–114 (average 85) species. The species were classified using an eight-class system reflecting their mean seed mass (MSM) records (class 1 being the lowest, MSM ≤ 0.2 mg; class 8 being the highest, MSM > 50 mg). Seed mass class distributions derived from slopes of contrasting aspect showed strong significant differences in chi-square tests for trend for all the four case studies. Small-seeded species (classes 1 and 2) showed a positive balance for the south-facing slopes, whereas large-seeded species (classes 5, 6, 7 and 8) were more frequent on north-facing slopes. Species with intermediate seed mass (classes 3 and 4) were not distinctive between the slopes. These results represent strong evidence of increased seed mass in the vegetation of north-facing grasslands, when compared to their south-facing counterparts. Among the phenomena potentially responsible for the new findings, we discuss the roles of microclimatic effects (especially drought stress and light regime), grass litter, interspecific competition and seed predation.

Effect-Directed Discovery of Bioactive Compounds Followed by Highly Targeted Characterization, Isolation and Identification, Exemplarily Shown for Solidago virgaurea

A nontargeted, effect-directed screening (bioprofiling) and a subsequent highly targeted characterization of antibacterial compounds from plant matrices is demonstrated on the example of Solidago virgaurea root extracts. The procedure comprises high-performance thin-layer chromatography (HPTLC) coupled with six bacterial bioassays including two plant pathogens, a radical scavenging assay, an acetylcholinesterase assay as well as in situ and ex situ mass spectrometric analyses. In situ mass spectra were directly recorded from the adsorbent using the Direct Analysis in Real Time interface (HPTLC-DART-MS), whereas ex situ mass spectra were recorded using an elution head-based interface (HPTLC-ESI-MS). For further bioassay-guided isolation of the main antimicrobial compounds, flash chromatographic fractionation and semipreparative high-performance liquid chromatographic purification were used and nuclear magnetic resonance data allowed the identification of the unknown antimicrobial compounds as 2Z,8Z- and 2E,8Z-matricaria esters. The discovered antibacterial activity was confirmed and specified by a luminometric assay and as minimal inhibitory concentration in the liquid phase.

Reasoning with direction and rate of change in vegetation state transition modelling

Abstract Better integration in land planning and management can be supported through the use of suitable model-based tools. Vegetation state transition models have been noted as being useful in this context, providing a simple, useful means of capturing available ecological knowledge. We describe a simple ‘proof of concept’ rule-based system developed to contribute methodologically to management-oriented modelling of vegetated landscapes. The system is based upon a clear separation of direction from rate of change and the use of a general temporal reasoning system, a feature that facilitates modelling of situations where environmental change occurs causing an increase or decrease in rate without affecting direction of vegetation change. To ease model development and use the system represents vegetation dynamics in a way that has a close correspondence to the structure of understanding communicated by vegetation ecologists. A test model is described and run under different conditions to demonstrate the system. The results show that although the rule-based system and in particular the temporal reasoning system used operate successfully, there are a number of deficiencies in the modelling system as currently implemented. Future development possibilities are detailed along with a broader discussion regarding the needs of management-oriented modelling and the utility of state transition approaches.

Puccinia komarovii var. glanduliferae var. nov.: a fungal agent for the biological control of Himalayan balsam (Impatiens glandulifera)

Clearly defining the taxonomic identity of a potential biocontrol agent is an essential component of any biological control programme. As part of such a programme against Impatiens glandulifera, a highly invasive annual weed in both Europe and North America, the rust fungus Puccinia komarovii was collected on this host plant in its native Himalayan range. However, current literature indicates that P. komarovii is a pathogen of a number of Impatiens species globally and was described originally from I. parviflora, a species native to Asia and now naturalized in Europe. Morphological comparisons, based on urediniospore and teliospore measurements, were generally inconclusive in showing any clear differences between the accession from I. glandulifera and those from other Impatiens species. Both, nrDNA ITS and ITS2-LSU sequence analyses indicated a difference between the rust infecting I. glandulifera compared to accessions on other hosts. However, the large variations in both ITS and 28S (ITS2-LSU) sequences determined within single accessions in this study, makes a clear separation difficult. Cross-inoculation experiments, using one accession of P. komarovii ex I. glandulifera (from India) and two accessions of P. komarovii ex I. parviflora (from China and Hungary), confirmed the specificity of these strains to their original hosts. Two Himalayan Impatiens species, I. scabrida and I. brachycentra, showed varying levels of susceptibility to these rust accessions, where the former was weakly susceptible to all three accessions and the latter was weakly susceptible only to P. komarovii ex I. parviflora (from China). However, commercial cultivars of I. balsamina proved to be fully susceptible to all rust accessions, although this has not been demonstrated under field conditions in India. Based on these host specificity differences between the rust accessions, we propose a new variety: Puccinia komarovii var. glanduliferae var. nov. associated with I. glandulifera in the Himalayas.

Soil seed bank of the invasive Robinia pseudoacacia in planted Pinus nigra stands

Abstract - Pinus nigra and Robinia pseudoacacia are exotic trees used for afforestation in Hungary. Pinus nigra was non-invasive, however R. pseudoacacia escaped from cultivation and invaded several vegetation types including pine plantations. It has recently been planned to cut P. nigra plantations and replace them by native tree stands, especially in nature reserves. The scattered presence of R. pseudoacacia specimens in pine stands might place constraints on planned tree replacement because of their vegetative resprouting and recolonization from an established seed bank. The aim of this study was to investigate the soil seed bank under the canopy of solitary R. pseudoacacia specimens found in P.nigra plantations. Altogether 250 soil samples were collected from the 0-6 and 6-12 cm soil layers under solitary Robinia trees of varying ages (with basal areas between 62.4 and 1089.3 cm2). Seeds were separated by sieving then scarified and germinated. Seed bank density ranged between 640 and 2285 seedsm-2 with an average distribution of 82.7% and 17.3% in the upper and lower soil layer, respectively. Total density of the seed bank and also the seed bank ratio of the lower soil layer increased with tree age. The accumulated seed bank of R. pseudoacacia should be considered in the careful planning of tree replacement operations in Pinus nigra stands.