Figure 1

Conceptional framework showing the hypothesized relationships between plant species richness and productivity in managed grasslands (after¹², 2002, modified). Main panel: If an originally species rich extensively managed grassland (I) experiences intensification, then productivity increases, whereas richness decreases, resulting in a negative relationship (see side panel 1). Reducing land-use intensity from an intensively managed grassland (II), would decrease productivity, but not alter species richness (due to e.g. seed bank limitations), resulting in a less negative or neutral relationship (see side panel 2 and a). By actively reintroducing new species in a grassland with reduced land-use intensity (III), we would expect richness (as well as the gradient in species richness) to increase, concomitantly leading to increases in biomass production (due to e.g. species complementarity). This would result in a positive relationship between species richness and productivity (see side panel 3 and b). Note that the species richness gradient in panel III is longer than in panel I and II, because of the species pool enrichment through introduction of new species. LUI land-use intensity of grasslands. Blue two-sided arrows represent relationships between species richness and productivity. Green arrows indicate gradient in land-use (high: dark green vs low: light green). Red dashed line represents the hump-backed model (Grime et al. 1973).