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.