Progressive effects of shading on experimental wetland communities over three years |
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Authors: | Kirsten A Edelkraut Sabine Güsewell |
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Institution: | 1. Geobotanical Institute ETH Zürich, Universit?tsstrasse 18, ETH Zentrum CHN G 28.2, CH-8092, Zürich, Switzerland
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Abstract: | To investigate how the composition of wetland communities changes over time in response to altered light regimes, experimental
communities of five Carex and four grass species were subjected to artificial shading (continuous or seasonal) in a three-year field experiment. Shoot
number and size was measured after six weeks, and shoot biomass was harvested five times during the experiment. Communities
were initially dominated by three grass species in all treatments, but subsequently, the Carex species increased and reached dominance in the control plots, whereas grasses remained dominant in the shaded plots. Shading
had no effect on the biomass of communities or of single species in the first year. In the second year, community biomass
was still unaffected, but shading reduced the biomass of three Carex species and also reduced species diversity. In the third year, shading reduced community biomass and all Carex species, but not species diversity. The greater shade tolerance of the grasses could not be explained by differences in morphological
plasticity: after six weeks of growth all species had increased shoot height in response to shade by 40–70%. Grasses were
hardly more plastic than Carex species. We propose that the long-term success of the Carex species in full light was due to a high allocation of biomass to belowground parts, which may have reduced losses caused
by repeated harvesting of shoots (a simulation of management in productive wet meadows). Shading probably caused the Carex plants to change their allocation pattern, and thus prevented their progressive increase. |
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Keywords: | Community structure Diversity Morphological plasticity Seasonal light availability Shade Succession Wetland vegetation |
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