Résumé
1. Understanding how functional traits, which are key for plant
functioning, relate to demographic parameters of populations is central to
tackle pending issues in plant ecology such as the forecast of the fate of
populations and communities in a changing world, the quantification of
community assembly processes or the improvement of species distribution
models. We addressed this question in the case of species from a
Mediterranean rangeland of southern France. 2. Changes in species
abundance in response to management intensification (fertilization and
increased grazing pressure) were followed over a 28-year period.
Probabilities of presence, and elasticities of the changes in the
probability of space occupancy to colonization and survival, which are
analogues of demographic parameters, were calculated for 53 species from
the time series of abundance data using a space occupancy model. Nine
quantitative traits pertaining to resource use, plant morphology,
regeneration and phenology were measured on these species and related to
demographic parameters. 3. The long-term dynamics of species in response
to management intensification was associated with major changes in
functional traits and strategies. Changes in the probability of occurrence
– analogous to population growth rate - were correlated with traits
describing the fast-slow continuum of leaf functioning. The elasticity of
population growth rate to colonization was significantly related to
reproductive plant height and seed mass, and to a lower extent, to leaf
carbon isotopic ratio. 4. Synthesis. The functional response of species to
management intensification corresponds to a shift along the second axis of
a recently identified global spectrum of plant form and function, which
maps, to some extent, onto the fast-slow continuum of life-history
strategies. By contrast, the elasticity of colonization relates to the
global spectrum axis capturing the size of organs. Seed mass contributes
to this axis and is assumed to relate to one of the important traits
structuring the reproductive strategy axis of life histories as well,
namely net reproductive rate. While this mapping between functional and
life-history traits is appealing, further tests in contrasting types of
communities are required to assess its degree of generality.