Do consumer-mediated negative effects on plant establishment outweigh the positive effects of a nurse plant?

Many studies demonstrated the importance of facilitative effect by nurse plant on seedling establishment. Few studies evaluated the negative effects of consumers on plant establishment under nurse plants by dealing with them during multiple demographic processes. We investigated the balance between the facilitative effect and negative effects of consumers during multiple demographic processes in Malawi in southeastern Africa. We chose as a nurse plant and compared it with three other microsites in tropical woodlands: (a dominant woodland species), (a woodland species), and a treeless site. We quantified the seed rain, postdispersal seed predation, germination, and seedling survival of ssp. (a common forest species). Within each microsite, we quantified the overall probability of recruitment. We also measured seedling abundance of ssp. . We found that exerted both positive and negative impacts on the establishment of ssp. . facilitated seed deposition, seed germination, and seedling survival. On the other hand, seed removal at postdispersal stage was highest under . Interestingly, also had positive effects on germination and seedling survival, but not on seed deposition. When we excluded the seed arrival stage from our estimation of the recruitment probability, the highest value was found under , not under . When we included the seed arrival stage, however, the order of recruitment probability between and was reversed. The probability was one order of magnitude higher under than under . Our estimation of the probability which included the seed arrival stage was consistent with natural patterns of ssp. establishment. Despite the presence of opposite effects, the net effects of on ssp. recruitment in tropical woodlands can be positive.