Influences of phosphorus and potassium deficiencies on the methanotrophic communities in rice rhizosphere

Abstract

Soil methanotrophs can modulate net methane (CH4) emissions in rice paddy fields, but their growth and development depend, to a great extent, upon the soil nutrient status. In this study, a pot experiment was conducted to explore how deficiencies in soil phosphorus (P) or potassium (K) affect the methanotrophic abundance (based on pmoA q-PCR), community composition (based on MiSeq high-throughput sequencing) and CH4 oxidation potential using historically severe P and K deficient paddy soils, respectively. The results showed that P deficiency induced a significant decrease in methanotrophic abundance and potential activity in both rhizosphere and bulk soils. Additionally, P deficiency also caused clear shifts in the methanotrophic community composition within the rhizosphere, where the relative abundance of type II methanotrophs (e.g., Methylocystis and Methylosinus) increased while type I (e.g., Methylomonas, Methylobacter and Unclassified_typeIb) decreased. In contrast, K deficiency did not significantly affect the methanotrophic potential activity and community composition in both rhizosphere and bulk soils. More interestingly, P or K deficiency, particularly P deficiency, narrowed the differences in the abundance and community composition between rhizosphere and bulk soils, implying that P and K deficiencies could attenuate the rhizosphere effects on methanotrophic communities by limiting rice plant growth. Collectively, our results indicated that soil P deficiency, would inhibit soil CH4 oxidation directly or indirectly through restricting rice plant growth, while K deficiency have slight effects on the activity and community composition of soil methanotrophs.