[1] Symbiotic nitrogen fixation (SNF) is the main natural source of nitrogen (N) in terrestrial ecosystems worldwide. Previous studies have shown that fixation of N by plants can be limited by the availability of phosphorus (P) in soils. We used global meta-analysis to investigate how P availability controls SNF. In experiments in which plants were grown in an artificial medium, severe P deficiencies in the nutritive solution ([PO 4 ] < 5-42 μM) depressed SNF flux through both a direct decrease in the plant fixation rate (i.e., decreased N fixed per unit of plant biomass) and an indirect effect (i.e., through plant biomass). In most experiments with plants grown in soils, SNF was proportional to plant biomass and was consequently only indirectly limited by P. Some cases using unfertilized and weathered soils (ultisols or oxisols), where plants were particularly P stressed, were an exception with both direct and indirect P limitations. Our global analysis of the P-SNF relationship indicated that P bioavailability commonly limited SNF flux. We conclude that the main driver of in situ P limitation is indirect via limitation of plant growth, except in certain cases where both indirect and direct constraints may play a role. These cases of severe P deficiency may be mainly found in weathered tropical soils of Africa and South America, probably in unfertilized croplands which are depleted in P due to repeated biomass harvests.Citation: Augusto, L., F. Delerue, A. Gallet-Budynek, and D. L. Achat (2013), Global assessment of limitation to symbiotic nitrogen fixation by phosphorus availability in terrestrial ecosystems using a meta-analysis approach, Global Biogeochem. Cycles, 27,[804][805][806][807][808][809][810][811][812][813][814][815]

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International audienceContext - While many woody perennials grow and reproduce in varying environments, their ability to modify their reproductive allocation under varying resource availability is unclear. Aims - This study aimed to demonstrate the occurrence of plasticity of reproductive allocation in a pioneer woody species (Ulex europaeus). Methods - We studied seed production in 144 plants under different irradiance and population densities. We measured their basal area, their whole shoot biomass and photosynthetic biomass, and their reproductive output (number of fruits per individual and number of seeds per fruit). Results - We found that newly produced photosynthetic biomass was influenced by environmental variation, which in turn determined plants' reproductive output. In addition, in low light conditions investment in reproduction was more reduced than investment in growth indicating plasticity of reproductive allocation. Conclusion - These results provide the first evidence for plasticity of reproductive allocation of a woody plant. It may lead to the ability of this pioneer species to survive and to continue to reproduce even at low rates in non-optimal shady habitats and to maintain a non-empty seed bank in forest systems with long unfavourable periods between two disturbances