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Broad-leaved forest communities of the territory of Tharandt near Dresden, Bundesrepublik Deutschland, are described on the basis of vegetation relevés and classed into eight associations. A comparison of the communities with similar ones described from other territories of Central Europe is made.

The Pilosella alpicola group includes four species (P. alpicola s.str., P. ullepitschii, P. rhodopea and P. serbica) with allopatric distributions (Alps, Balkans, Carpathians) and contrasting cytotype patterns (diploid, diploid-polyploid and polyploid species). Whereas diploid taxa (P. ullepitschii and P. serbica) reproduce sexually, the mode of reproduction of polyploid cytotypes reflects their origin: autopolyploids of P. rhodopea reproduce sexually, while allopolyploid cytotypes of P. alpicola s.str. apomictically. We used allozymes to elucidate overall genetic variation within the group and to test their utility for taxon discrimination, assessment of polyploid origin and possible correlations with breeding systems. Variation of five allozyme systems encoded by eight polymorphic loci and 29 alleles was studied in 20 populations and 298 plants representing all taxa. Allozymes were proved to be only of limited usefulness for the taxonomic classification within the P. alpicola group. The Western Carpathian populations of P. ullepitschii formed the only genetically well-differentiated group. The same allele suite shared by all cytotypes of P. rhodopea and presence of both balanced and unbalanced heterozygotes in tetraploids was consistent with autopolyploid origins of polyploids and provided further evidence for a primary contact zone. An isolated relic population of P. rhodopea from the Southern Carpathians exhibited lowered values of genetic diversity when compared to the core area. Pronounced fixed heterozygosity was found in P. alpicola s.str., supporting its allopolyploid origin. In accordance with assumptions, genotypic variability was significantly higher in sexually reproducing diploid and diploid-polyploid taxa than in apomictic P. alpicola s.str.

Disjunct populations of the perennial herbGypsophila fastigiata L. (Caryophyllaceae) on the Baltic island of Öland were monitored during a thirteen-year study. The main objectives were to analyze the dynamic features ofG. fastigiata within and among sub-populations in shorter and longer time perspectives, and to relate this to habitat characteristics and patterns in local weather variation. The total number of individuals decreased and the proportion of reproductive individuals increased throughout the study period. Recruitment and mortality on a fine spatial scale (0.25 m2) were negatively correlated to species richness and vegetation cover. Rapid changes in population sizes were observed during and after summers with low precipitation. The highest mortality rates were found in pre-reproductive stages whereas relatively many of the adult plants survived the droughts. The long-term trend of population decline inG. fastigiata could be a result of changes in vegetation structure due to changing grazing regimes. It might also be an effect of more frequent dry summers during the second half of the observation period or of an interaction between weather and changes in management. Another interpretation is that dynamic processes are taking place on a geographic scale not covered in the present study.

Mowing a meadow is an example of an equalizing process that reduces differences among species by removing aboveground biomass approximately 5 cm above ground. This regular disturbance that affects all plants prevents competitive exclusion of small species and thus allows coexistence of numerous species differing in shoot size. In this paper we search for the mechanism behind this by comparing the shoot biomass of 41 common species in dry and wet species-rich meadows in mown and recently abandoned plots in June (before mowing) and in October. We asked the following questions: i) Do the plants differ in proportion of biomass lost by mowing? ii) Are the mown plants able to compensate for biomass lost by mowing? iii) Is the compensatory ability of mown plants related to their size? iv) Is the compensatory ability of plants related to severity of disturbance (removed biomass)? v) Does water availability in meadows affect these features? Our results revealed that the earlier explanation of equalization of meadow plants after mowing due to the proportionally larger biomass loss in larger plants than small plants does not represent the entire mechanism. Even when larger plants in the wet meadow lost more biomass, the proportion of lost biomass was not dependent on plant size, and compensation ability (growth of mown in comparison with unmown plants) was not related to the lost biomass in this meadow type. On the contrary, the observed pattern could be explained by different compensation abilities of small versus tall plants. In addition, according to our expectations, the compensation for lost biomass in the wet meadow was higher than in the dry one.

Knowledge of ploidy level and genome size in a germplasm collection is critical before studying genetic diversification of different environmental range in grasses and other plants. We assessed the geographic patterns in ploidy level and genome size of 216 individuals of Cynodon dactylon (L.) Pers. (common bermudagrass) by flow cytometry of accessions sampled from 16 geographic sites along a latitudinal gradient from 22°35′ N to 36°18′ N across China. Flow cytometry histograms combined with mitotic chromosome observations results show that tetraploids were the most frequent ploidy level, constituting 44.91% of all individuals. Nuclear DNA contents were 2.384, 2.419, 2.437, 2.873 and 3.288 pg/2C for the diploid, triploid, tetraploid, pentaploid and hexaploid, respectively. Higher proportions of polyploid individuals were observed within populations at the highest and lowest latitudes. In addition, monoploid genome size of C. dactylon progressively increased with increasing ploidy level. Temperature and precipitation had the influence on ploidy level for all the sites. The relationship between ploidy level and geographic distribution for C. dactylon will facilitate the utilization of this species for biological and genetic research.

This paper gives an overview of current research into the biology of hemiparasiticOrobanchaceae, formerly part of theScrophulariaceae. It is based on presentations and discussions that took place during the First International Symposium on non-weedy hemiparasiticOrobanchaceae in April 2004 in Wageningen. Aspects such as taxonomy and evolution, ecophysiology, population and restoration ecology are discussed, thus identifying challenges for future research. Hemiparasites have very different life histories, and the robust molecular phylogeny will now permit testing hypotheses regarding the evolution of these life histories, degree of parasitism and host specialization. In a number of genera, evolution is in full swing, leading to taxonomical complications, but at the same time offering opportunities for phylogeographical research. In ecophysiology, the challenge is to better understand what makes a good host and to investigate further the chemical signals emitted by the host and their use in regulating parasite development. Finally, the results of sowing hemiparasites to speed up the restoration of nutrient-poor grasslands are still very variable, and we need a more thorough understanding of the factors influencing population dynamics, which should also enable us to devise better management plans for threatened hemiparasitic species.

Repeated vegetation maps and phytosociological relevés recorded in the 1950s and again from 1984 to 2006 in a wet meadow complex near the town of Třeboň, in the southern part of the Czech Republic, central Europe were compared. The following trends were evident: original vegetation zones disappeared, as well as vegetation typical of less intensively used sites, i.e., short-sedge marshes and Deschampsia cespitosa meadows. Instead, stands with Phalaris arundinacea, Urtica dioica, Elytrigia repens, and species-poor Alopecurus pratensis meadows, as well as woody species, expanded as a result of either too intensive use (cutting, manuring) or abandonment. The number of 46 meadow and marsh species recorded in 1956 in repeated relevés was reduced to one-third, while ruderal and weedy species increased from zero to 22, thus surpassing the meadow and marsh species being now more numerous than the former ones. The large degradation that started in the late 1970s continues, with there being no chance of recovery unless the present management regime stops manuring and implements appropriate regular cutting once or twice a year.