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Ecological sorting of species along climate and landscape gradients is a fundamental global pattern. However, the extent to which functional traits reflect floristic turnover in response to interactions between climate and landscape gradients is rarely assessed. We tested whether floristic variation among sites within a bioregion was more strongly correlated with soil fertility or climate. We then examined the relationship between floristic composition, environment and the co-variation of selected vegetative and regenerative functional traits. This allowed us to assess the ecological sorting of species along soil fertility and rainfall gradients and to detect any resource compensation effects via interactions between these factors. Floristic differences were equally associated with soil fertility and climate contrasts but species’ trait patterns were more strongly associated with soil fertility than rainfall. No interactive effects, which would suggest resource compensation, were detected. Instead, more fertile sites consistently had more forbs, annuals and grasses in comparison with less fertile sites which were dominated by woody species and had a higher abundance of graminoids. Three broad mechanisms for sorting of species based on trait patterns are proposed (1) differences in the fundamental regenerative and growth niche, (2) resource competition during establishment and (3) disturbance-mediated sorting. |
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