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Cat’s claw creeper vine, Dolichandra unguis-cati (L.) Lohmann (syn. Macfadyena unguis-cati (L.) Gentry) (Bignoniaceae), is a major environmental weed in Australia. Two distinct forms of this weed (‘long’ and ‘short’ pod), with differences in leaf morphology and fruit size, occur in Australia. The long pod form has only been reported in less than fifteen localities in the whole of south-east Queensland, while the short pod form is widely distributed in Queensland and New South Wales. This study sought to compare growth traits such as specific leaf area, relative growth rate, stem length, shoot/root ratio, tuber biomass and branching architecture between these forms. These traits were monitored under glasshouse conditions over a period of 18 months. Short pod exhibited higher values of relative growth rates, stem length, number of tubers and specific leaf area than long pod, but only after 10 months of plant growth. Prior to this, long and short pod did not differ significantly. Higher values for these traits have been described as characteristics of successful colonizers. Results from this study could partly explain why the short pod form is more widely distributed in Australia while long pod is confined to a few localities.
Central European dry grasslands are remarkably diverse plant communities that occur at the western edge of the Eurasian forest-steppe zone and harbour many species of continental distribution. Although their plant community types have been described in detail, the diversity patterns and their environmental determinants are still poorly known for these grasslands. Here, we study environmental drivers of species composition and richness in dry grasslands of northern Bohemia (České středohoří Mts) and central Bohemia (Křivoklát region), both in the Czech Republic. In vegetation plots of 100 m2 we recorded all vascular plant species, measured soil chemistry variables, above-ground biomass production and nutrient concentrations in biomass. Species richness in these plots ranged from 13 to 55. The relationships between species composition and the environment were explored using detrended correspondence analysis and canonical correspondence analysis, while the relationships between species richness and the environment were assessed using univariate and multiple regression models. In both regions, species composition and richness strongly responded to the soil pH (ranging from 4.0 to 7.8), which was positively correlated with calcium and magnesium concentrations and negatively with annual precipitation. The response of species richness to soil pH was unimodal with a peak at pH of about 6.5 in the České středohoří Mts, and positive in the Křivoklát region. Plots on soils with a pH higher than 5 consistently contained more than 35 species. In the České středohoří Mts, species richness was positively related to the aboveground biomass production, whereas in the Křivoklát region, this relationship was only significant for graminoid species. In both areas, plots with soils deeper than 20 cm and with aboveground biomass dry weight above 200 g/m2 harboured more than 40 species per 100 m2. Moreover, in the České středohoří Mts, nitrogen concentrations in the biomass had considerable effects on both species composition and richness: species numbers were lower at sites with higher nitrogen concentration. This indicates a threat to diversity of these dry grasslands under currently high atmospheric nitrogen deposition coupled with the absence of management at most of the studied sites.