1. Agricultural intensification is one of the main causes of biodiversity loss worldwide. Despite the introduction of semi-natural features in agricultural landscapes may have potential negative effects on yield production, this practice is commonly suggested to enhance farm biodiversity. However, there is little evidence for the effect of semi-natural features on other components of biodiversity such as functional diversity. Yet this could provide a more comprehensive understanding of the biodiversity-productivity trade-off.
2. Here, we report the effect of semi-natural woody vegetation on taxonomic and functional diversity, and biomass production of herbaceous species at the field and the farm scale by sampling 50 fields, ranging from 0 to 90 % woody vegetation cover, on nine similarly managed farms in Central-Western Spain.
3. We found significant differences in the richness of herbaceous species among farms. Both taxonomic and functional β-diversity, exhibited significant negative relationships with herbage production, highlighting the trade-off between biodiversity-productivity in the studied agroecosystems.
4. Woody vegetation cover had a significant negative relationship with biomass production and a unimodal relationship with species richness at the field scale. At high values of woody vegetation cover, species richness and functional diversity indices were decoupled suggesting that at this extreme of the gradient of woody vegetation, only herbaceous species with contrasted trait values were present . Our results showed both convergent and divergent patterns of trait values, suggesting that different assembly processes are acting concurrently along the gradient of woody vegetation.
5. Synthesis and applications: Our result suggests that the management of woody vegetation can have direct consequences on both taxonomic and functional diversity, yet with detrimental effects on herbage production. The optimisation of the trade-off between herbage diversity conservation and productivity can be reached with a woody vegetation cover near 30 % at the field scale.
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