Effects of litter species and genetic diversity on plant litter decomposition in coastal wetland

Abstract

With the enhancement of carbon sink capacity and the intensification of biodiversity change in coastal wetlands, previous studies have well studied the relationship between species diversity and litter decomposition, a vital process of carbon cycling. However, previous studies ignored the importance of genetic diversity, which restricted our comprehensive understanding of the effects of biodiversity loss on ecosystem functions. Here, we manipulated different richness levels with litters of eight common species of coastal wetland plants and eight different genotypes of common reed (Phragmites australis) to explore the effects of species and genetic diversity on litter decomposition. We found the litter mass loss of mixtures was significantly lower than the average mass loss of single litters (ANOVA, p < 0.05), suggesting higher species and genetic diversity had negative effects on plant litter decomposition. The negative effects were also supported by the t-test that the observed mass loss was significantly lower than expected at both species and genetic diversity levels, which also identified that antagonistic effects occurred. In addition, the functional diversity of initial litter qualities, such as lignin content and the C/P ratio, had a significant correlation with the negative effects at species and genetic levels, whereas phylogenetic diversity did not reveal such a correlation, implying functional diversity might better predict the effects of diversity changes on litter decomposition in coastal wetlands at both species and genetic levels. Furthermore, the presence of specific species or genotype litters, such as Scorzonera mongolica, Imperata cylindrica and the common reed numbered CN2026, could also predict negative effects. In this study, we found that genetic diversity influenced litter decomposition as much as species diversity, and we provided significant implications for predicting the effect of wetland biodiversity loss or conservation on carbon sink capacity.

Keywords

• Litter decomposition
• Species diversity
• Genetic diversity
• Multiple dimensional diversity
• Initial litter quality