Functionally dissimilar organisms (FDO) interact with plant communities simultaneously, both above and below the ground. Some have bottom-up effects driven by resources, others top-down effects driven by consumption. So far, the relative importance of FDO at a community level is far from understood. We conducted full-factorial mesocosm studies to investigate the individual and combined impacts of FDO on the structure and productivity of grassland plant communities.
Results/Conclusions
FDO affected the diversity and productivity of grassland plant communities differently, mostly independent of each other. Opposite effects cancelled each other out, and were mainly additive. The results suggest different niches of FDO leading to independent impacts on ecosystem functions. More studies on interactive impacts of FDO are needed to weigh their relative importance for ecosystem functioning and answer the question whether bottom-up or top-down factors have stronger impacts on diversity and productivity of grassland plant communities.