Mountain ash forests of the Central and Southern Alps: Grisons-Ticino (Switzerland)-Verbano-Cusio-Ossola (North Italy)

Mountain ash (Sorbus aucuparia) is widespread in nearly whole Europe from sea level to timberline. On north exposed peaks of some mountains the Southern Alps (Ticino/ Switzerland and North Italy/ Verbano-Ossola) small mountain forests build forest limit above 1500 m, so at Monte Lema, Morissolo, I Balmit Mottarone. often occurs on former clearings as pioneer tree secondary plant succession. sites, mountain ash will be replaced later by beech climax species. At all we recognized a weak or missing generative reproduction. One reason for that could dense grass cover small-reed, Calamagrostis spec. which inhibits establishment rowan seedlings; other reasons insect game damage, mycosis diseases. Vegetative propagation like root bulbils, suckers shoots stump are important survival strategies ash. So, sites have been recorded high share polyphyletic single young trees. count annual rings 25-50 trees revealed an average age 40-55 years. Green alder occur together within Alnetum viridis well forest. In green bush, only trees, whereas Alnus can dominate both communities. southernmost there marked abundance due dryer climate. Within Alps, typical tall perennial herbs bush more less absent because low rainfall during summer possibly absence alder. driest grow species, mainly small-reed (Calamagrostis spec.). Based our vegetational surveys mentioned above, suggest new sub-association Alno viridi-Sorbetum aucupariae calamagrostietosum prov. eventually association Calamagrostio-Sorbetum