Effect of biochar feedstock on microbial carbon metabolism in a phosphorus-limited soil: Insights from ecoenzymatic stoichiometry and isotope-based microbial carbon use efficiency

Abstract

Through the input of carbon (C), nitrogen (N), and phosphorus (P), biochar can alter the stoichiometric imbalance between available resources and microbial elemental demands, thereby influencing microbial metabolism. However, how biochar affects microbial C use efficiency (CUE) and its linkage with microbial respiration across different feedstocks remains unclear. This study investigated the impacts of biochars (from pig manure (MB), peanut shell (PB), corn straw (CB), bamboo (BB), and wood (WB)) on soil microbial respiration, enzyme activity, and CUE estimated by an ¹⁸O-H₂O labeling approach (CUE-¹⁸O) and an ecoenzyme stoichiometry model (CUE_C:N or CUE_C:P) in a P-limited forest soil. Over 120 days, MB and PB biochars enhanced microbial respiration and biomass C, while other biochars had weak effects on them. MB and PB treatments significantly increased soil P availability and decreased C:P imbalances. Moreover, MB and PB alleviated microbial P limitation and increased CUE-¹⁸O and CUE_C:P. Partial least squares path modeling indicated that decreased C:P imbalance and microbial P limitation contributed greatly to microbial respiration via enhancing microbial CUE_C:P rather than CUE-¹⁸O. Overall, our findings underscore the critical role of biochar feedstock in regulating short-term microbial C metabolism, providing insights for the understanding of the effects of biochar on soil C flux in P-limited forest soils.

Graphical abstract

Keywords

biochar feedstocks / C:N:P stoichiometry / stoichiometric imbalance / microbial CUE

Highlight

	● Manure and peanut shell biochars stimulated soil microbial biomass and respiration.
	● Manure and peanut shell biochars alleviated microbial P limitation.
	● Biochar effects on microbial CUE depend on the estimation methods.
	● Decreased P limitation contributed to microbial CUE and soil CO2 emission.

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