Summary

Post-dispersal seed predation can cause severe seed losses in plant populations. However, it is unclear to what extent such losses can help to lower weed densities, as an aid in weed control in agroecosystems. 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 this proposal 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 seed cohorts, in terms of seedling recruitment and establishment, in the absence and presence of granivores will be monitored in maize fields over the course of three years. A range of seed densities will be applied to assess the degree of seed limitation. The relationship between seed and plant densities will be corrected for density dependent granivory. The results of this study should clarify whether it is worthwhile to invest in measures to preserve and enhance the ecosystem service granivory.

Funding agency; Deutsche Forschungsgemeinschaft
Project leader; Paula R. Westerman

PhD students
Heike Pannwitt
Christian Selig

MSc students                                                     BSc students
Eric Höft                                                               Dennis Conrad
Christoph Seifert