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Notes:
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Questions: Is plant diversity in mesic grassland ecosystems
vulnerable in the short-term to extreme climate change events?
How rapidly can responses in vegetation composition occur in
perennial grasslands? Are the expected compositional changes
related to rare species losses or to shifts in the relative abundance
of the dominants?
Location: Subalpine mesic grasslands on limestone in the
Pyrenees.
Methods: Transplanting turves from the upland, with coldtemperate
climate, to a lowland location, with continental
Mediterranean climate.
Results: Transplanting led to decreased biodiversity and strong
shifts in vegetation composition. Results from both permutation
tests and traditional multivariate analysis suggested different
trajectories of vegetation depending on the initial species pool.
Vegetation showed a tendency to converge in composition in
the lowland over time, independently of initial differences.
Estimated changes in relative biomass of the five most abundant
species between the upland and the lowland ranged from
–89 to +96 %. The ensemble of all other species was reduced
by 80%. The most dominant species in the upland, Festuca
nigrescens, reduced its abundance in the lowland, shifting
from having mainly positive to mainly negative associations
with other species.
Conclusions: Mesic grassland ecosystems in the Pyrenees
showed strong shifts in plant diversity and composition after
a short period of warming and drought, as a consequence of
acute vulnerability of some dominant grasses, losses of rare
species, and aggregate and trigger effects of originally uncommon
forb species.
This work was partially supported by the Technological Forestry Centre of Catalonia, the Paeria de Lleida and a fellowship to MTS from the Catalan Government for a short-term visit to UCD. |
