Abstract
Sensitive responses among bacterial and fungal communities to pyrogenic organic matter (PyOM) (biochar) addition in rhizosphere and bulk soils are poorly understood. We conducted a pot experiment with manure and straw PyOMs added to an acidic paddy soil, and identified the sensitive “responders” whose relative abundance was significantly increased/decreased among the whole microbial community following PyOM addition. Results showed that PyOMs significantly (p < 0.05) increased root growth, and simultaneously changed soil chemical parameters by decreasing soil acidity and increasing biogenic resource. PyOM-induced acidity and biogenic resource co-determined bacterial responder community structure whereas biogenic resource was the dominant parameter structuring fungal responder community. Both number and proportion of responders in rhizosphere soil was larger than in bulk soil, regardless of PyOM types and microbial domains, indicating the microbial community in rhizosphere soil was sensitive to PyOM addition than bulk soil. The significant increased root biomass and length caused by PyOM addition, associated with physiological processes, e.g. C exudates secretion, likely favored more sensitive responders in rhizosphere soil than in bulk soil. Our study identified the responders at fine taxonomic resolution in PyOM amended soils, improved the understanding of their ecological phenomena associated with PyOM addition, and examined their interactions with plant roots.
Highlights
Pyrogenic organic matter (PyOM) is widely distributed in agricultural lands[1] and fire-affected natural soils[2], which can constitute up to 80% of total soil organic carbon[3]
Previous studies mainly focused on pyrogenic organic matter (PyOM) effects on microbial community in bulk soils[22,23], and rarely considered root physiological processes induced by PyOM addition, e.g. rhizodeposition
We mainly focused on the relative abundances of six bacterial taxa (i.e. Acidobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Alphaproteobacteria and Betaproteobacteria) and three fungal phyla (i.e. Ascomycota, Basidiomycota and Zygomycota) because they are widely distributed in soils with high relative abundance[28]
Summary
Pyrogenic organic matter (PyOM) ( called biochar) is widely distributed in agricultural lands[1] and fire-affected natural soils[2], which can constitute up to 80% of total soil organic carbon[3]. Previous studies mainly focused on PyOM effects on microbial community in bulk soils[22,23], and rarely considered root physiological processes induced by PyOM addition, e.g. rhizodeposition. The carbon products secreted by facilitated growing roots, which are preferential nutrients and energy for microbial metabolism, can affect microbial community in rhizosphere soil In this process, PyOM would simultaneously play a critical direct and indirect role due to its unique properties. Whitman et al.[27] used this concept to demonstrate how mineralizable carbon induced more bacterial responders than PyOM in soils In this sense, the responders of microbial community in response to PyOM addition were speculated to be different between rhizosphere and bulk soils. Our objectives were to: (1) identify the responders among bacterial and fungal microbiome that are sensitive to PyOM addition at fine level of taxonomic resolution; (2) examine how the bacterial and fungal responder communities respond to PyOM addition; (3) investigate the difference and similarity of responder communities between rhizosphere and bulk soils, and examine the potential mechanisms involved
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