Impacts of native and alien plant dominants at different spatial scales

Plant invasion science has made a substantial progress in documenting the impacts of aliens, but comparisons with the impacts of native dominants are still rare. Further, the impacts on larger spatial scales remain poorly understood. We recorded the impacts of 10 native and nine invasive dominant plants in the Czech Republic on species richness and Shannon diversity by comparing communities with high vs. low cover of the dominant species. To estimate the impacts at the (i) population level and (ii) between-population level, we compared the Jaccard dissimilarity, nestedness and turnover of high- and low-dominance plots. Further, we calculated the Jaccard dissimilarity, nestedness and turnover between the high- and low-dominance plots within each population to express the impacts on species composition. We tested whether (i) native and invasive dominants affect the population- and between population levels of diversity by making the vegetation more homogenous; (ii) whether these effects differ between the native and alien dominants; and (iii) whether the impacts at different spatial levels are related. At the population level, high-dominance plots (with both native and alien dominants) showed higher nestedness and lower turnover compared to the low-dominance plots. Further, all plots with native dominants, both with high- and low dominance, showed higher similarity but lower nestedness than plots with alien dominants. Most importantly, high-dominance plots with native dominants were more similar to each other but showed marginally significantly lower nestedness compared to high-dominance plots with alien dominants. At the between-population level, high-dominance plots with native dominants showed a marginally significantly lower turnover compared to high-dominance plots with alien dominants. The differences in Jaccard dissimilarity, nestedness and turnover between the low- and high-dominance plots at the population level showed strong positive relations to low- and high-dominance differences at the between-populations level. Further, compositional impacts, expressed as the dissimilarity between high- vs. low-dominance plots, positively related to the plot-level impacts on Shannon diversity. Our results show that (i) both native and invasive dominants tend to reduce the diversity over larger areas and that the effect of native dominants may be even stronger, and (ii) the effects on plot-level richness and diversity cannot be easily extrapolated to larger scales but the impacts at the population- and between-populations levels are positively related

Long-term changes of forest vegetation - the comparison of present species composition and biodiversity with the historical records

The thesis presents the results of the research of the long term changes in semi-natural vegetation of lowland woodlands in the forest district Klínec (phytogeographical district Střední Povltaví, Central Bohemia, Czech Republic), which is located between the northeastern part of the Brdy Highlands (Hřebeny) and the Vltava River valley. Research of the long term changes over the past nearly 60 years was conducted by resampling vegetation on semi-permanent plots. Old relevés by V. Samek (1957), which were provided by the Czech National Phytosociological database, were used as reference data. Twenty-nine relevés were resampled, which were located using old data and GIS. The shift to shady plant communities (loss of heliophilous and expansion of shade-tolerant species) was found in the study area caused by higher canopy of tree and shrub layer due to the expansion of deciduous trees. Species richness (alpha diversity) was significantly declined. Homogenization of the vegetation was not significantly demonstrated in study area. Species of nutrient-rich habitats as well as alien and invasive species were expanded and fewer red list species of vascular plants was found. Vegetation change in the area was probably most affected by the change in forest management in lowland woodlands (decline of coppicing), eutrophication (deposition of nitrogen from the atmosphere, runoff from agricultural land) and the effect of forest animals especially wild boars

Biotic threats to garden monuments: algae, cyanobacteria and invasive plant species

Chateau, city parks and gardens are perceived as harmonious parts of the landscape. Unfortunately, even these areas have to face various threats, and they can be a threat to the surrounding environment. The exhibition /catalogue presents a look at the organisms that threaten parks. These threats cover unwelcomed invaders covering invasive plants and small microorganisms in the soil, on facades, statues or in water. On the other hand, some species that are intentionally brought to the parks can be risky not only the gardens themselves but also their surroundings