Seed rain dynamics reveals strong dispersal limitation, different reproductive strategies and responses to climate in a temperate forest in northeast China

Questions: Species co-existence may be achieved by limited dispersal due to the reduced chance of inter-specific competition. But the timing of seed release also provides clues for species co-existence because asynchronous reproduction can alleviate inter-specific competition for dispersal agents, while synchronous reproduction can facilitate overall seed dispersal. How strong is seed dispersal limitation, do co-existing species release seeds synchronously or asynchronously, and what is the relationship between seed production and main meteorological measures? Location: A 25-ha plot in a temperate forest, Changbai Mountain, Northeast China. Methods: We calculated Jaccard coefficients between seed rain composition and neighbouring adult tree composition, analysed long-term seed rain dynamics for both the whole community and different species, and regressed seed rain density with meteorological measures using autoregressive models. Results: The Jaccard coefficient dropped sharply as neighbourhood radius increased to about 10 m, indicating severe dispersal limitation. Both synchrony and asynchrony in seed release were observed: most species released mature seeds synchronously from August to November, with small segregations in time; one species released seeds in Jun. Bimodal and unimodal seasonal dynamics of seed rain were observed and some species released seeds beyond the main fruiting seasons. The seasonal dynamics of seed release might be driven by different strategies of seed dispersal. Seed rain density is significantly positively related to temperature and precipitation, with a 2-mo time lag. Conclusions: Both dispersal limitation and timing of seed release by co-existing species may contribute to maintenance of diversity of this forest, but variations in temperature and precipitation considerably alter seed rain density.