Interaction Between Plants Through Litter Input in Mangrove Succession in the Red River Delta

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ABSTRACTAimsDominant or pioneer species litter decomposition was found to be involved in the recruitment of following species during succession in terrestrial plant communities, while knowledge remains scarce in wetland forests such as mangroves. Our study evaluated the influence of pioneer species leaf litter decomposition on (i) the settlement success of species following them or not in the natural succession and (ii) on soil characteristics.LocationRed River Delta, Vietnam.MethodsWe set up an in situ experiment in mesocosms that followed the survival and growth of three species (Kandelia obovata, Aegiceras corniculatum, and Rhizophora stylosa) planted in soils of Avicennia marina or Sonneratia caseolaris, with or without leaf litter addition for 203 days. Soil nutrient contents were determined at the beginning and end of the experiment, and their metabolic fingerprints were compared using an untargeted metabolomic approach to highlight potential allelochemicals when a phytotoxic effect was observed.ResultsSeedling response to litter addition was species‐specific, which can be linked to their successional status. K. obovata was most affected by litter addition, showing better growth with both litter types. Meanwhile, A. marina litter substantially decreased survival rates by 50% for K. obovata and 33% for R. stylosa, suggesting a strategy to delay its replacement by these species through the release of phytotoxic decomposition by‐products. Metabolic fingerprints of A. marina soils planted with K. obovata showed no shift in global chemical composition, but 12 features were found significantly more abundant in the presence of litter. Putative annotations revealed sulfur‐containing metabolites, which are probable products of organic matter sulfurization, a frequently occurring process in mangrove sediments. These unusual compounds may act as allelochemicals and should be further assessed.ConclusionsOur findings suggest that allelopathic processes through litter decomposition may be at play in mangrove community assembly and could be a tool for restoration purposes.