The Evolve model was used to simulate the relationship between soil fertility and species diversity, and between diversity and yield. In the first set of simulations, the effect of soil nutrient status (N=15-225 in arbitrary units of soil fertility) on the ability of diversity to evolve was investigated. Mutations in life history traits were allowed to occur in 1 of 500 propagules. In simulation 1, diversity was allowed to evolve under intense grazing. In simulation 2, the community of species that had evolved at the end of each of the first set of simulations were transplanted into a fertile environment (N=225). Each of these communities was then allowed to interact for a further 100 years, but this time with no mutations occurring. In the final year of the simulation, the aboveground biomass of the grassland was recorded on a monthly basis. At the end of the first set of simulations, the evolution of species diversity was more pronounced in grasslands with the most fertile soil. These highly fertile and diverse grasslands produced the highest levels of biomass, while grasslands characterized by low levels of species diversity and soil fertility produced almost no biomass. After 100 years of plant competition in the second set of simulations, June biomass production was found to be weakly and negatively correlated with species richness. However, when total annual biomass production was considered, the highest yields were observed to be associated with the most diverse grasslands. These diverse communities were consistently more productive across the entire year than the less diverse grasslands.
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Breeding for resilience: a strategy for organic and low-input farming systems? EUCARPIA 2nd Conference of the Organic and Low-Input Agriculture Section, 2010