Pyrolysis temperature of biochar affects ecoenzymatic stoichiometry and microbial nutrient-use efficiency in a bamboo forest soil

• Published in: Geoderma Vol. 363; p. 114162
• Main Authors: Guo, Kangying, Zhao, Yingzhi, Liu, Yang, Chen, Junhui, Wu, Qifeng, Ruan, Yifei, Li, Songhao, Shi, Jiang, Zhao, Lin, Sun, Xuan, Liang, Chenfei, Xu, Qiufang, Qin, Hua
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: acidity; bacteria; bamboos; Biochar; CUE; dissolved organic carbon; Ecoenzymatic stoichiometry; enzyme activity; forest soils; fungi; microbial biomass; NUE; Nutrient availability; nutrient use efficiency; Phyllostachys violascens; pyrolysis; Pyrolysis temperature; soil amendments; soil enzymes; soil pH; structural equation modeling; temperature; total nitrogen; Nutrient availability; Pyrolysis temperature; CUE; Biochar; Ecoenzymatic stoichiometry; NUE
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2019.114162

•Microbial nutrient-use efficiencies were compared among biochars in a forest soil.•Ecoenzymatic stoichiometry reveals a nutrient limitation for microbes under biochar.•Biochar prepared at 500 °C and 700 °C increased microbial C-use efficiency.•Biochar prepared at 350 °C and 500 °C increased microbial N-use efficiency.•Effect of biochar on microbial metabolic activity was pyrolysis temperature dependent. A microcosm study was performed to investigate changes in soil enzyme activities and microbial C- and N-use efficiencies (CUE and NUE) with amendment of biochars prepared at three pyrolysis temperatures (350, 500 and 700 °C) in an acid bamboo (Phyllostachys praecox) forest soil. The results showed that, compared to the non-amended control, biochars produced at 500 and 700 °C significantly (P < 0.05) increased soil pH, total N, and dissolved N (DN) concentrations, whereas significantly decreased dissolved organic C (DOC) and exchangeable acidity concentrations after three months. The microbial biomass C (MBC) and N (MBN) and the ratio of fungi: bacteria (F:B) were only significantly increased under 350 °C biochar. The ratios of both soil C:N and DOC:DN to MBC:MBN were reduced under 500 and 700 °C biochars, suggesting a lower C:N imbalance between resources and microorganism. The ratio of C- to N-acquiring enzyme activities increased gradually under biochars with increasing temperature. Moreover, microbial CUE increased whereas NUE declined under biochars at 500 and 700 °C, and the threshold elemental ratio (TER) revealed that the microbial nutrient metabolisms were limited by N in soils amended with residue, but were limited by C under biochars at 500 and 700 °C. Structural equation modeling indicated that the C:N imbalance had a great impact on microbial CUE, while changes in F:B ratio and soil pH were closely associated with NUE. This study suggests that changes in microbial nutrient-use efficiency and ecoenzymatic stoichiometry reveals a clear C-limitation, but a N-availability under short-term amendment of biochar produced at a high pyrolysis temperature.