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Article Dans Une Revue Oikos Année : 2011

Niches of temperate tree species converge towards nutrient-richer conditions over ontogeny

Résumé

Niche changes during a species 'lifespan are known as ontogenetic niche shifts. These shifts reflect changes in resource availability, requirements, organisms' foraging ability and/or size-dependent biotic interactions. In the plant kingdom, however, this issue remains poorly covered. We investigated nutritional niche shifts over the ontogeny of 23 temperate tree species (among nine phylogenetic families) by a synchronic approach. We used 1963 temporary phytoecological surveys conducted throughout metropolitan French forests. The realised niches of three life-history stages (seedling: < 0.5 m; sapling: < 0.5 m and < 8 m; tree: > 8 m) in each tree species were modelled on the basis of presence/absence data and the main factors of species distribution (energy, water and nutritional resources). We computed the nutritional optima and amplitudes by bootstrapping partial response curves for the C:N ratio and base saturation rate. We assessed changes in these niche parameters over ontogeny and also evaluated the relative importance of ontogenetic shifts in the differentiation of nutritional niche among the selected tree species. The tree stage was found to occur mainly at higher nutrient availability than the seedling (+ 16.3% on the nutritional gradient) or sapling (+ 11.1%) stages. In addition, nutritional niches of tree species exhibited, successively, a niche enlargement in eutrophic conditions and a niche restriction in oligotrophic conditions during growth. These global nutritional niche shifts observed over the species' lifespan contributed moderately but significantly to the niche separation in temperate tree communities (up to 4.5%). We interpreted niche shifts as a response to an increase in nutritional requirements over ontogeny, leading to an intraspecifi c selection where individuals established in eutrophic soils have the maximal fitness. Biotic interactions and temporal changes in the environment may secondarily enhance or counteract the process. The importance of ontogenetic niche shifts requires consideration in the study of species autecology and plant community organisation.

Dates et versions

hal-01000546 , version 1 (04-06-2014)

Identifiants

Citer

Romain R. Bertrand, Jean-Claude J.-C. Gégout, Jean-Daniel Bontemps. Niches of temperate tree species converge towards nutrient-richer conditions over ontogeny. Oikos, 2011, 120 (10), pp.1479-1488. ⟨10.1111/j.1600-0706.2011.19582.x⟩. ⟨hal-01000546⟩
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