Discussion
Our study revealed high similarity in fitness-environment relationships among species, and greater within-species variation in vital rate responses to abiotic conditions than plant-plant interactions. We found weak but frequent evidence of demographic trade-offs between emergence and seed production across a local-scale gradient from shaded, fertile plots to sun-exposed, lower-fertility plots. Competitive effects on survival and seed production were surprisingly rare, and effects on population growth depended on abiotic conditions for half of the species. Altogether our results highlight the importance of interactive abiotic and biotic factors for plant demography in a diverse annual plant system. Our results also demonstrate the risk of assuming fitness responses based on a single vital rate.