Soil microbial communities influencing organic phosphorus mineralization in a coastal dune chronosequence in New Zealand

The Haast chronosequence in New Zealand is a ∼6500-year dune formation series, characterized by rapid podzol development, phosphorus (P) depletion, and a decline in aboveground biomass. We examined bacterial and fungal community composition within mineral soil fractions using amplicon-based high-throughput sequencing (Illumina MiSeq). We targeted bacterial non-specific acid (class A, phoN/phoC) and alkaline (phoD) phosphomonoesterase genes and quantified specific genes and transcripts using real-time PCR. Soil bacterial diversity was greatest after 4000 years of ecosystem development and associated with an increased richness of phylotypes and a significant decline in previously dominant taxa (Firmicutes and Proteobacteria). Soil fungal communities transitioned from predominantly Basidiomycota to Ascomycota along the chronosequence and were most diverse in 290 to 392-year-old soils, coinciding with maximum tree basal area and organic P accumulation. The Bacteria: Fungi ratio decreased amid a competitive and interconnected soil community as determined by network analysis. Overall, soil microbial communities were associated with soil changes and declining P throughout pedogenesis and ecosystem succession. We identified an increased dependence on organic P mineralization, as found by the profiled acid phosphatase genes, soil acid phosphatase activity, and function inference from predicted metagenomes (PICRUSt2).