XVI International Botanical Congess

Alnus is a characteristic plant genus of trees commonly distributed on wet and dry sites, respectively, in the temperate zone of the northern hemisphere. Efficiency of root aeration in seedlings by pressurized ventilation differ very much among the species. Ventilation rates are high in species commonly distributed in wetlands, but low in those species which are restricted to well drained sites. From these results pressurized ventilation and its beneficial physiological effects should be seen as an adaptation mechanisms for establishing seedlings of wetland species on water-saturated soil and frequently flooded sites which provides a significant ecological advantage to these tree species to use wetlands as refuges for avoiding the strong competition in terrestrial ecosystems.