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Schlagwörter:
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Zusammenfassung:
Questions: Numerous grassland biodiversity experiments have explored how
plant diversity influences colonization by vascular plants, but no such studies
have examined how sown vascular plant diversity structures colonization by
bryophytes, which can contribute greatly to grassland diversity.
Location: Grassland biodiversity experiment (Jena Experiment), Germany.
Methods: We studied bryophyte composition in experimental grasslands
encompassing a gradient of vascular plant species richness (1, 2, 4, 8, 16 and 60
species), functional group richness and composition (1 to 4; grasses, legumes,
tall herbs, small herbs) as well as in additional bare ground and spontaneously
colonized plots and semi-natural controlmeadows.
Results: Increasing vascular plant species richness and functional group richness
as well as the presence of legume species decreased bryophyte species richness
and increased the spatial variability of this richness. Bryophyte species
richness and cover responded positively to grass presence, which also decreased
the spatial variability of both. The proportion of acrocarpous species was largest
in bare ground plots and decreased with increasing vascular plant species richness
and with grass and legume presence. Non-metric multidimensional scaling
revealed that bryophyte species composition followed the gradient in sown vascular
plant species richness and was dependent on grass and legume presence.
The effect of plant diversity on bryophytes was only partly attributable to
increased vascular plant species cover. Bryophyte habitat indicator values suggested
that conditions in communities of higher vascular plant diversity that
included grasses weremore shady,moist and nutrient-rich than in communities
with lower vascular plant diversity and without grasses, whereas bryophyte
assemblages in communities with legumes indicated well-lit nutrient-rich conditions.
Even after six years, bryophyte species richness and cover was considerably
lower in experimental grasslands than in semi-natural meadows,
suggesting a role for dispersal limitation or habitat filtering.
Conclusions: Our study shows that bryophyte colonization is not random,
rather it is structured by vascular plant species diversity and composition. Not all
components of a plant community respond positively to increased vascular plant
diversity and advocating increased richness of one taxonomic group over
another in grasslandmay reduce net species diversity.