Regulation of soil aggregate size under different fertilizations on dissolved organic matter, cellobiose hydrolyzing microbial community and their roles in organic matter mineralization

摘要

The mineralization of soil organic matter is closely related to climate change. Labile organic matter and microbial community are vital intrinsic factors in controlling the mineralization of soil organic matter. Regulation of soil aggregate size on dissolved organic matter (DOM), the cellobiose hydrolyzing microbial community, and their roles in organic matter mineralization remains unclear. The mineralization of organic matter in large macroaggregates (LMA. ＞2 mm), small macroaggregates (SMA, 0.25-2 mm), and microaggregates (MI, ＜0.25 mm) from an Ultisol treated with long-term non-fertilizers (Ck), chemical fertilizers (NPK) and animal manure (AM) was observed in this study. The concentration and structure of DOM, activity of β-glucosidase, and the abundance, diversity, and community composition of GH1 (glyco-side hydrolase family 1) microbial β-glucosidase encoding genes were investigated. The cumulative CO_2-C emissions occurred in the order LMA ＜ SMA ＜ MI in each fertilization treatment and followed the sequence Ck ＜ NPK ＜ AM in each size of aggregate. The concentration of DOM in the soil aggregates increased as the aggregate size decreased, while the structural complexity of DOM followed the opposite trend. The activity of β-glucosidase in the smaller aggregates was higher than that in the larger aggregates, and the abundance and diversity of the GH1 microbial β-glucosidase genes generally echoed the same trend. The dominant microbial classes harboring GH1 β-glucosidase genes in the soil aggregates were Actinobacteria, Alphaproteobacteria, Gammaproteobacteria, Flavobacteria, Eurotiomycetes, and Sordariomycetes. The relative abundance of Actinobacteria, Sordariomycetes, and Eurotiomycetes revealed significant differences among the aggregates. Redundancy analysis confirmed that microbial GH1 β-glucosidase community in the soil aggregates was primarily regulated by DOM concentration and pH. Structural equation modelling revealed that soil aggregates mainly regulated the β-glucosidase activity and DOM concentration and then the abundance and diversity of the GH1 microbial β-glucosidase genes in controlling organic matter mineralization.