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Litter mixing effect on decomposition rate and nutrient release to water: low quality leaves of coastal species
  • Lili Wei

Abstract

Non-additive effect on litter decomposition often occurs in mixed terrestrial communities but little investigated on coastal ecosystems. We selected three common mangrove species and one alien saltmarsh species from a coastal wetland stand to test whether non-additive effect occurs when the litters of these coastal species mixed together. To avoid the heterogeneity of soil conditions and to detect nutrient release into water, we conducted an in vitro litter-bag experiment in a glasshouse. Among three litter mixtures, the non-additive effect was observed in the litter mixture composed of mangrove species Aegiceras corniculatum vs. Kandelia obovata (antagonistic) and A. corniculatum vs. Avicennia marina (synergistic), but not in the litter mixture of A. corniculatum vs. Spartina alterniflora (the alien saltmarsh species). The strength of non-additive effect was unrelated to litter initial trait dissimilarity. Instead, litter decomposition rate and mass remaining of litter mixtures were strongly related to the community-weighted mean of leaf carbon. The nutrients and carbon released into water were more likely controlled by litter decomposition rate rather than by litter initial nutrient concentrations. These findings would lead to the expectations on ecosystem scale that the mangrove stand mixed with A. corniculatum and K. obovata accumulates more organic carbon in the sediment and releases less nutrients into water column than the stand composed of A. corniculatum and A. marina . It is also implying that the alien species S. alterniflora invasion may not reduce soil carbon stock of mangrove forests. These hypotheses need to be further tested and which will be suggestive for the protection or reconstruction of coastal wetlands.