Tomas Herben (Charles University, Hokkaido University at present)
00/12/07, 13:30-
at Room No.3631 (6th floor of the 3rd building of the Faculty of Sciences)
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Unlike trees, aboveground parts of most of the clonal plants are of
limited size. They interact by occupation of space in horizontal direction;
their interactions are made complex by spatial constraints due to their
horizontal growth and by that fact that individual aboveground plants may
share resources by rhizome systems belowground. We attempted to identify
interactions among species of clonal plants in two types of mountain
grasslands (species-rich and species-poor) by means of removal experiments
and implant experiments. In the removal experiments, always one species was removed. Since the vegetation cover was rather fine-grained, no large (~>5 cm) gaps have been opened in the community due to the removal. The response of the remaining species to release from competition was observed both at a fine-scale (3 x 3 cm plots to detect the filling in of the microgaps made by the removal) and large scale (25 cm plots). Plants responded in two ways: (i) by increasing number of their modules in the microhabitats previously occupied by the removed species, and (ii) by increasing number of their modules with little or no difference between microhabitats previously occupied by the removed species and those not occupied. The response of clonally growing species was stronger at the fine scale, meaning that these species were selectively increasing their density at the patches where the initial density of the removed dominant was high. Some species responded consistently negatively to removal of some other species; this may be due either to indirect effects in the community or to positive interactions between that species and the removed dominant. Implant experiments were done with vegetatively multiplied plants of Festuca rubra that were back-transplanted into the community; the implants were put into sites differing in the neighbouring species composition. Several clones were used in the experiment. The experiment showed that (i) growth of the implants was affected both by the biomass of the neighbours and by the species composition; identical biomass of different species of neighbours did not necessarily have the same effect, (ii) the variation among individual clones in their growth parameters and response to neighbours was different. |