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We propose a rapid sampling method to assess the functional composition of herbaceous plant communities without prior knowledge of the floristic composition. To determine the community-level value of traits (‘aggregated trait values’) for a plant community, a standardized population-centred method exists, but requires substantial manpower and reliable botanical knowledge. We tested an alternative method, the trait transect, using four subalpine pastures in the Beaufortain region (Northern French Alps) selected along a fertility gradient. We applied both methods to measure five commonly used ‘soft traits’ known to be responsive to soil nutrient availability: plant vegetative and reproductive height, specific leaf area, leaf dry matter and nitrogen contents. We tested whether the variation of these traits along the gradient detected with the population-centred method was also detected with the trait transect. Both methods detected expected trends in the traits in response to the fertility gradient. The trait transect method was as efficient as the population-centred method and is recommended as an appropriate tool for monitoring ecosystem changes in response to environmental conditions and management, especially in species-rich communities. [ABSTRACT FROM AUTHOR]

Question: Are leaf dry matter content, specific leaf area and leaf life span relevant plant traits to discriminate the fertility gradient in species-rich natural grasslands? In other words, is species ranking conserved when nitrogen availability or growing periods change? Location: Toulouse Research Centre, France; 150 m a.s.l. Methods: Fifteen grasses and nine dicotyledons were sown in pure stands in a random block design with three replicates. Each species was cultivated at two levels of nitrogen supply, limiting and non-limiting for growth, with three replications per nitrogen level. Leaf traits were measured across both levels of nitrogen supply and growing periods over the year. Results: Leaf dry matter content values separated the species into three life-form classes (grasses, rosette forbs and upright forbs, P < 0.001). This was not the case for specific leaf area and leaf life span. The three leaf traits were variable across growing periods and nitrogen levels, but the ranking of species was conserved over N-levels and growth periods. Furthermore leaf dry matter content was always less variable than the other leaf traits. Conclusion: We conclude that leaf thy matter content measured only on grasses could be used as an indicator to describe the N-richness of the habitat where native herbaceous vegetation develops. [ABSTRACT FROM AUTHOR]