Acidification associated with plant phosphorus-acquisition strategies decreases nutrient cycling potential of rhizosphere bacteria along the Hailuogou post-glacial chronosequence

Abstract

Background and aim

Soil nutrient availability, acidification associated with plant phosphorus-mining strategies, and fine root foraging all influence nutrient cycling. However, their relative impacts on microbial nutrient cycling during primary succession remain unclear.

Methods

We studied a 130-year primary succession along the Hailuogou post-glacial chronosequence in southwest China. Early-successional stages (1–3) are dominated by Hippophae tibetana, which is gradually replaced by Populus purdomii. In the climax community (stage 4), Abies fabri replaces P. purdomii. We collected rhizosphere soil, roots, and leaves from the dominant species, analyzing how phosphorus-acquisition strategies (proxied by soil pH, leaf manganese concentration and fine-root morphology) influenced bacterial nutrient-cycling gene abundance, based on 16S rRNA sequencing.

Results

Rhizosphere pH and the abundance of genes encoding enzymes involved in ammonium and nitrate assimilation, denitrification and phosphorus mobilization were significantly lower for H. tibetana and A. fabri than for P. purdomii. In contrast, P. purdomii exhibited a significantly higher specific root length. Linear mixed models reveal that leaf manganese concentration was positively correlated with soil acidification. Multiple regression models show that nutrient-cycling potential was more significantly linked to soil pH than to fine-root morphology or soil nutrient availability. Structural equation models indicate that the reduced nutrient-cycling potential was indirectly associated with soil acidification through bacterial co-occurrence networks rather than bacterial richness.

Conclusion

Soil acidification, associated with phosphorus-mining strategies of H. tibetana and A. fabri, may inhibit microbial nutrient-cycling potential during primary succession. This highlights the interactions between plant nutrient-acquisition strategies and microbial processes in shaping terrestrial nutrient cycling.