Abstract
Direct and indirect plant–plant interactions play important roles in structuring plant communities, but the relative importance of physical stress and biological disturbance in mediating competitive outcomes remains debated. We conducted two common garden experiments to examine the influence of salinity and disturbance (sediment accretion and clipping) on competitive interactions among three native sedges (Scirpus mariqueter, Scirpus triqueter, and Carex scabrifolia) in the Yangtze estuary. In both experiments, the relative competitive abilities of these plants shifted among different treatments. Competition importance rather than intensity significantly decreased with increasing stress. At the community level, competition importance showed reduced variation along the stress gradient in the disturbance experiment. Notably, the performance of these sedges in three-species mixtures could not be predicted by their competitive relationships in two-species mixtures, which was an indication of indirect interactions. Salinity, disturbance and indirect interactions all affected the competitive dynamics of these sedges, which could explain their different performances and natural distributions in the Yangtze estuary. Our findings of the complex effects of physical factors and multi-species interactions, as well as the different patterns of competition importance along stress gradients at the species level and the community level can improve our understanding of plant community organization in salt marshes and other ecosystems with sharp environmental gradients.
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Acknowledgments
We would like to thank Mark D. Bertness and the anonymous referees for their very helpful comments on an earlier version of this paper. This study was financially supported by the National Basic Research Program of China (Grant No. 2013CB430404), the National Science Foundation of China (Grant Nos. 30930019 and 31100317) and Ministry of Education (Grant No. 20120071110017) and the Science and Technology Commission of Shanghai Municipality (Grant No. 14DZ1206003).
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CHW and BL conceived and designed the experiments; CHW performed the experiments; and CHW and BL analyzed the data and wrote the manuscript.
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Communicated by Laura Gough.
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Wang, Ch., Li, B. Salinity and disturbance mediate direct and indirect plant–plant interactions in an assembled marsh community. Oecologia 182, 139–152 (2016). https://doi.org/10.1007/s00442-016-3650-1
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DOI: https://doi.org/10.1007/s00442-016-3650-1