Plant reproduction under elevated CO2 conditions:: a meta-analysis of reports on 79 crop and wild species

Reproductive traits are key characteristics for predicting the response of communities and ecosystems to global change. We used meta-analysis to integrate data on eight reproductive traits from 159 CO2 enrichment papers that provided information on 79 species. Across all species, CO2 enrichment (500-800 mul l(-1)) resulted in more flowers (+19%), more fruits (+18%), more seeds (+16%), greater individual seed mass (+4%), greater total seed mass (+25%), and lower seed nitrogen concentration, (N) (-14%). Crops and undomesticated (wild) species did not differ in total mass response to elevated CO2 (+31%), but crops allocated more mass to reproduction and produced more fruits (+28% vs +4%) and seeds (+21% vs +4%) than did wild species when grown at high CO2. Seed [N] was not affected by high CO2 concentrations in legumes, but declined significantly in most nonlegumes. Our results provide robust estimates of average plant reproductive responses to CO2 enrichment and demonstrate important differences among individual taxa and among functional groups. In particular, crops were more responsive to elevated CO2 than were wild species. These differences and the substantial decline in seed [N] in many species have broad implications for the functioning of future natural and agro-ecosystems.