Response of nitrifier and denitrifier community to Epichloë endophytes mediated host litter decomposition under phosphorus addition treatments

Nutrient availability plays a crucial role in both litter decomposition and decomposer communities. However, the specific effects of Epichloë endophytes on soil decomposer communities during the decomposition of their host litter under fertilized conditions are still unclear.

In this study, qPCR combined with Illumina sequencing was conducted to reveal the responses of functional gene communities involved in organic P recycling (phoD), nitrification (AOA/AOB-amoA), and denitrification (nirS/nirK) to Epichloë gansuensis-mediated decomposition of Achnatherum inebrians litter under different P addition treatments. Meanwhile, soil physicochemical properties and enzyme activities were measured.

Both E. gansuensis infection and P addition exerted limited effect on the abundance and diversity of phoD-harboring microbial community. In the E. gansuensis-free (E−) samples, 60 mM P addition significantly increased the gene copies of AOA-amoA and significantly decreased those of AOB-amoA. Additionally, P addition decreased the richness and diversity of the nirK-harboring community in the E− samples, while E. gansuensis appeared to alleviate this response. P addition decreased the relative abundance of nirS-harboring Acidovorax and Azospirillum, while increasing the nirK-harboring Rhodopseudomonas and Bosea. Mantel’s test showed that E. gansuensis infection decreased the correlation between nitrifier communities and soil properties. Furthermore, nirS- and nirK-harboring communities showed a similar correlation pattern with soil properties in both E+ and E− soil samples.

This study demonstrates the important roles of E. gansuensis on nitrifier and denitrifier communities during its host grass decomposition under different P nutrient conditions, facilitating our comprehensive understanding of the ecological significance of Epichloë endophytes.