Biochar-derived dissolved organic matter (BDOM) shifts fungal community composition: BDOM-soil DOM interaction

Abstract

Biochar-derived dissolved organic matter (BDOM is a highly reactive proportion of biochar, which can affect the microbial community composition in soil. Despite this, the mechanisms by which BDOM influences soil fungal communities and DOM dynamics remain poorly understood, limiting its effective application in soil management practices. In a microcosm experiment, we investigated the direct effect of biochar-derived dissolved organic matter (BDOM), instead of solid biochar matrix, on the fungal community composition, soil nutrient bioavailability, and soil dissolved organic matter (SDOM). The BDOM was derived from bone, plant, and manure and generated at low and high pyrolysis temperatures (LPT, HPT). LPT-derived BDOM revealed higher BDOM contents in the following order: rice husk (RB) > rabbit manure (MB) > sheep bone (SB) compared with HPT, causing higher SDOM contents in the soil. Fungal diversity indices were reduced, particularly with MB-derived BDOM. A significant shift in microbial taxonomy was observed at both the phylum and genus levels with the addition of BDOM. A higher abundance of Mortierellomycota (1.98-fold increase), Basidiomycota (1.39-fold increase), and Chytridiomycota (2.61-fold increase) was noticed with all added BDOM, except for MB-derived BDOM, compared to no BDOM addition. At LPT, the higher abundance of Mortierellomycota was linked to increased phosphorus availability in the order of SB400 > MB400 > RB400, compared to the control. Higher values of fluorescence (Flul), freshness (FrI), biological (BIX), and humification (HIX) indices were associated with LPT-derived BDOM, particularly SB-derived BDOM, while HIX was notably enhanced with MB-derived BDOM. These findings revealed that BDOM-induced changes in SDOM and its interaction with the fungal microbiome play a key role in soil organic matter dynamics, nutrient cycling, and soil quality.