Cultivar mixtures increase stability through asynchrony and intensify productivity over time
Description
Crop cultivar mixtures commonly increase productivity in the short term and stabilize and increase productivity in the long term, but these effects can be highly variable. This may be due to a poor understanding of the underlying mechanisms for such diversity effects. We explored mechanisms for the effects of cultivar mixtures on the temporal stability and intensification of productivity in a seven-year (2016-2022) field experiment with maize in Northwest China. Across all cultivar mixtures over the seven years, grain yield and aboveground biomass increased by 5.6% and 3.6%, respectively, compared to the monocultures, stability increased during the later years (2019-2022). Grain yield intensified by 35% and aboveground biomass by 38%, compared to monocultures. Complementarity effects were strong and increased over time. The mean values of functional traits changed in response to mixtures, leading to plant height and ear height traits correlating positively with complementarity effects, which were correlated with temporal yield stability. Asynchrony, or variation in the responses of cultivars to environmental fluctuations, was higher in four-and eight-cultivar mixtures than in two-cultivar mixtures, and negatively correlated with the deviation in temporal yield. These results indicated that cultivars with large differences in mean trait values or that express dynamic trait responses to diversity can increase complementarity effects and asynchrony, producing more productive and stable crops. This increases our understanding of how intraspecific diversity might contribute to sustainable agroecosystems.