Endangerment of thermophilous flora even under conditions of increasing environmental temperatures

As mentioned earlier, it is not true that some bulbous species from the family Orchidaceae are able to survive only mycotrophically, i. e. without formation of stalk. Our observations, especially of Ophrys apifera, have demonstrated (in the Czech Republic) that the durability of adult plants is very short so that their numbers are fluctuating. The dying can be caused by several factors. Frost damages followed by rotting of underground parts (roots and bulbs) are relatively frequent. The leaf rosette, which is the most resistant, dies as the last, usually later in the spring of the following year. This means that the frost damage is often not identified during the cursory visually control in the spring. We observated very extensive damaging and dying of the Orchidaceae after the winter of 2002/03 - on the turn of November and December 2002, there was a rapid onset of very strong black frost after a long, wet and relatively mild autumn. Consequently 80% of population perished. None specimens of Ophrys apifera and/or Himantoglossum adriaticum came into blossom in 2003 and other species were strongly damaged. Our observations document that the general increase in air temperatures need not result in the occurrence of generally expected better growing conditions for some thermophilous species. It is very probable that the extremes climatic conditions could show greater effects than the general increase in average temperatures. Such phenomena are well-known but in practice they are not noticed and/or are explained in a different way. Such risks can exist in the whole Central European region. Negative effects of frosts in winter 2002/03 were further intensified by long and extreme droughts in the growing season of the year 2003. Combination of these extremes was crucial for the species Gentianella bohemica: In average, 95% of specimens in each population perished. If the fluctuations in climatic conditions will be more frequent, some species can become extinct irreversibly very quickly.