Effects of herb Alternanthera philoxeroides invasion on soil organic matter varied with flooding conditions in wetlands

Abstract

Background and aims

Wetlands play a crucial role in the global cycling of carbon and nitrogen, and plant invasions, as one of global change factors, often affect the structure and function of wetland ecosystems. Accordingly, this study aims to reveal the impacts of plant invasions on the carbon sequestration capacity of wetlands with different flooding conditions.

Methods

We investigated the effects of a typical invasive plant, Alternanthera philoxeroides, on the carbon and nitrogen of soil organic matter (SOM) components under different flooding conditions (flooded, meaning permanently flooded; non-flooded, meaning seasonally flooded) in a constructed wetland. The associated physicochemical factors and microbial community characteristics were studied to explore the underlying mechanisms of the impacts of plant invasion on SOM.

Results

The invasion of A. philoxeroides significantly increased the soil dissolved organic carbon (DOC) in both flooded and non-flooded habitats. Furthermore, the invasion of A. philoxeroides increased the carbon and nitrogen content of soil particulate organic matter (POM) and SOM in the non-flooded habitats, while there were no such differences in the flooded habitats. In addition, plant invasion had no significant effect on mineral-associated organic matter (MAOM) in both flooded and non-flooded habitats, but the flooding could promote the formation of MAOM in the invaded habitats.

Conclusion

In non-flooded habitats, plant invasion significantly increased SOM by increasing the carbon and nitrogen content of POM, and in flooded habitats, flooding reduced the effects of plant invasion in increasing SOM components except the soil DOC.