Testing for the weed control potential of seed predators in agroecosystems

Abstract: Post-dispersal seed predation can cause severe seed losses in plant populations. However, it is unclear whether such losses can help to lower weed densities, as an aid in weed control in arable fields. Seed predators could be removing seeds that would have died anyway, that would never have germinated or whose seedlings would never have reached reproductive maturity. It leads back to the paradigm whether a plant population is seed or microsite limited, which can be tested by the classical seed addition experiment. If seed additions lead to higher plant densities, a population is said to be seed limited; if they do not, it is said to be microsite limited. The proportion of added seeds that germinates and gets established is indicative of the degree of seed limitation. The main objective of our research is to examine if and to what extent weeds in maize are seed limited; granivory only matters if weeds are predominantly seed limited. The fate of a single seed cohort of Echinochloa crus-galli, applied at a range of densities, in terms of seedling recruitment and establishment, in the absence and presence of granivores will be monitored in two maize fields over the course of three years. Furthermore, demographic rates of E. crus-galli will be estimated and used to parameterize a population model for the same maize system. The two approaches will be compared. The results of this study should clarify whether granivory contributes to weed control and is, thus, an ecosystem service and worthwhile promoting.