Exotic tree seedlings are much more competitive than natives but show underyielding when growing together

Abstract

Aims Invasive species continue to be a worldwide threat to ecosystems mainly as a cause for biodiversity loss. Forest ecosystems, for example, are subject to a change in species composition due to the invasion of exotic species. s pecifying the attributes that cause the strong competitiveness of several exotic species may improve the ability to understand and effectively manage plant invasions in the future. In this study the following hypotheses were tested: (1) biomass production of below- and aboveground plant compo nents of the exotic tree species is higher than that of the natives, resulting in a higher competitiveness of the exotics; (2) the exclu sion of root competition has a positive effect on the biomass pro duction of the inferior native species; and (3) mixtures of native and exotic species yield a higher biomass production than the respective monocultures. Methods a pot experiment, containing about 2000 tree seedlings, was established. We investigated the biomass productivity and growth reactions of two native ( Quercus robur l., Carpinus betulus l.) and two exotic tree species ( Prunus serotina Ehrh., Robinia pseudoacacia l.) in different intra- and interspecific, competitive situations with and without the influence of root competition. Important Findings