Interacting effects of soil acidity and canopy cover on the species composition of field-layer vegetation in oak/hornbeam forests

Abstract

The distribution and quantity of the more-important field-layer species in south-Swedish oak/hornbeam forests (135 sites) are related to soil acidity and canopy cover (CC) characteristics, reflecting the interacting influence of soil chemical properties and stand management. The total cover of the field-layer vegetation is mainly a function of the CC, soil pH playing only a slightly modifying role. The number of field-layer species, however, increases considerably with soil pH at low to average CC values. At high CC values, Convallaria majalis is the dominating species except at high pH, where it is replaced by Mercurialis perennis. Vaccinium myrtillus and Deschampsia flexuosa alternate as dominants in sites with low pH + low CC values, whereas several species may attain dominance in the intermediate ranges of the two variables. Oxalis acetosella, at low CC values almost unrelated to pH, does not occur at high pH + high CC, probably due to competition from Mercurialis perennis. It is concluded that soil acidity to a large extent accounts for the floristic composition of the field-layer vegetation, though canopy cover may greatly modify these relationships.