Plant and microbial interactions under different planting patterns regulate nitrogen removal in constructed wetlands

Area of Science:

• Environmental Science
• Microbiology
• Ecology

Background:

• Constructed wetlands are vital for nitrogen pollution control.
• Plant-microbe interactions are key, but microbial mechanisms in different planting patterns are unclear.

Purpose of the Study:

• To investigate how different aquatic macrophyte planting patterns affect nitrogen removal and microbial communities in constructed wetlands.
• To elucidate the microbial mechanisms driving nitrogen removal under monoculture versus mixed planting.

Main Methods:

• Laboratory-scale constructed wetlands were established with monocultures and mixed plantings of aquatic macrophytes.
• Nitrogen removal, mass balance, and microbial community/functional gene dynamics were assessed using 16S rRNA sequencing and quantitative PCR.

Main Results:

• All planted systems outperformed the unplanted control in total nitrogen removal.
• Mixed planting showed slightly improved nitrate and COD removal; microbial transformation contributed significantly (28%), with plant uptake increasing under mixed conditions.
• Mixed planting enhanced microbial diversity, enriched key nitrogen-cycling bacteria (e.g., Nitrosomonas, Paracoccus), and increased functional gene abundance, indicating strengthened microbial robustness.

Conclusions:

• Planting patterns reshape microbial guild contributions to nitrogen removal rather than uniformly enhancing it.
• Plant diversity in constructed wetlands promotes microbial functional robustness and stability.
• Findings provide mechanistic insights for optimizing ecological design of constructed wetlands for improved nitrogen mitigation.