Patterns of Fraxinus angustifolia in an alluvial old-growth forest after declines in flooding events

Abstract

The main focus of this paper was the dynamics of Fraxinus angustifolia tree spatial patterns after the frequency of flooding events has markedly declined, especially as regards competition with Carpinus betulus and Acer campestre, the most rapidly expanding species in alluvial hardwood forests in Central Europe. The study was conducted in alluvial forests at the confluence of the Morava and Dyje rivers in the Czech Republic. A pair correlation function was used to describe the variability in tree density. Analyses were carried out for datasets from 1973, 1994 and 2006. Over the study period, F. angustifolia populations were characterised by stagnation in the number of individuals, while the number of C. betulus and A. campestre trees increased. Recruitment rates of F. angustifolia were the lowest of all species with the exception of Quercus robur. Recruits of F. angustifolia showed a strong connection to newly available space after decay of the Q. robur layer. Analysis of the elevational distribution of populations showed an increase in the stand intersection of tree species. In the absence of regular floods, F. angustifolia comes into direct competition with C. betulus and A. campestre, which are more adapted to grow in densely shaded, closed stands.