Macroaggregates Serve as Micro-Hotspots Enriched With Functional and Networked Microbial Communities and Enhanced Under Organic/Inorganic Fertilization in a Paddy Topsoil From Southeastern China

Abstract

Microbial communities of soil aggregate-size fractions were explored with molecular and networking assays for topsoil samples from a clayey rice paddy under long-term fertilization treatments. The treatments included no fertilizer (NF) as control, chemical fertilizer only (CF), chemical fertilizer with swine manure (CFM), and chemical fertilizer with rice straw return (CFS). Following a wet-sieving protocol, water-stable aggregates were separated into size fractions of large macroaggregates (L-MacA, >2,000 μm), macroaggregates (MacA, 2,000–250 μm), microaggregates (MicA, 250–53 μm), fine microaggregates (F-MicA, 53–2 μm), and fine clay (F-Clay, <2 μm). Mass proportion was 32.3–38.2% for F-MicA, 23.0–31.5% for MacA, 19.0–23.1% for MicA, 9.1–12.0% for L-MacA, and 4.9–7.5% for F-Clay, respectively. The proportion of MacA was increased, but F-Clay was reduced by fertilization, whereas the mean weight diameter was increased by 8.0–16.2% from 534.8 μm under NF to 621.5 μm under CFM. Fertilization affected bacterial 16S rRNA and fungal 18S rRNA gene abundance in F-MicA and F-Clay but not in aggregates in size larger than 53 μm. However, bacterial and fungal community α-diversities and community structures were quite more divergent among the fertilization treatments in all size fractions. Organic carbon and gene abundance of bacteria and fungi were enriched in both L-MacA and MacA but depleted in F-Clay, whereas microbial Shannon diversity was rarely changed by fraction size under the four treatments. L-MacA and MacA contained more bacteria of r-strategists and copiotrophs, whereas F-MicA and F-Clay were demonstrated with a higher abundance of K-strategists and oligotrophs. Guilds of parasitic and litter saprotrophic fungi were enriched in F-MicA but depleted in L-MacA. Furthermore, most of bacterial and fungal operational taxonomic units were strongly interacted in L-MacA and MacA rather than in MicA and F-Clay. Thus, MacA acted as micro-hotspots enriched with functional and networked microbial communities, which were enhanced with organic/inorganic fertilization in the rice paddy.

Green manuring increased peanut yields and reduced soil carbon mineralization by optimizing microbial communities

“…For P treatment, the 1 − 2 mm aggregate harbored higher DOC and N levels (Table 3) and supported the most abundant Rhizobiales (genus Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium) and Xanthomonadales (genus Dyella) (Table S6), which were assigned to the copiotroph (r-strategists) using labile forms of C for growth and metabolism, and grew faster in a nutrient rich environment (Fierer et al 2007), thus determining the higher K c compared with other aggregates. This was consistent with a previous study reporting that the 1 − 2 mm aggregate was a hotpot in a fragmented soil environment with a higher SOC mineralization rate (Rui et al 2022).…”

Shifts in maize microbial communities and networks are correlated with the soil soil chemical property under different fertilization regimes

“…In addition, the ecological network of microbial communities is now a priority area of soil ecology research. In recent years, it has been widely used to study the interaction between soil organisms in different ecological environments, in which species (i.e., nodes) are connected by pairwise interactions (links) (Feng et al, 2017;Rui et al, 2022). Based on this analysis, we can not only determine the symbiotic patterns of characteristic microbial species at different taxonomic levels (Lupatini et al, 2014;Fan et al, 2018), but also identify the key species that affect the stability of the microbial community (Banerjee et al, 2018;Liu et al, 2022).…”