Feng Jiao, Yu Dailin, Sinsabaugh Robert L, Moorhead Daryl L, Andersen Mathias Neumann, Smith Pete, Song Yanting, Li Xinqi, Huang Qiaoyun, Liu Yu-Rong, Chen Ji
College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China.
Department of Biology, University of New Mexico, Albuquerque, NM, 87102, USA.
Biol Rev Camb Philos Soc. 2023 Aug;98(4):1184-1199. doi: 10.1111/brv.12949. Epub 2023 Mar 13.
Biochar amendment is one of the most promising agricultural approaches to tackle climate change by enhancing soil carbon (C) sequestration. Microbial-mediated decomposition processes are fundamental for the fate and persistence of sequestered C in soil, but the underlying mechanisms are uncertain. Here, we synthesise 923 observations regarding the effects of biochar addition (over periods ranging from several weeks to several years) on soil C-degrading enzyme activities from 130 articles across five continents worldwide. Our results showed that biochar addition increased soil ligninase activity targeting complex phenolic macromolecules by 7.1%, but suppressed cellulase activity degrading simpler polysaccharides by 8.3%. These shifts in enzyme activities explained the most variation of changes in soil C sequestration across a wide range of climatic, edaphic and experimental conditions, with biochar-induced shift in ligninase:cellulase ratio correlating negatively with soil C sequestration. Specifically, short-term (<1 year) biochar addition significantly reduced cellulase activity by 4.6% and enhanced soil organic C sequestration by 87.5%, whereas no significant responses were observed for ligninase activity and ligninase:cellulase ratio. However, long-term (≥1 year) biochar addition significantly enhanced ligninase activity by 5.2% and ligninase:cellulase ratio by 36.1%, leading to a smaller increase in soil organic C sequestration (25.1%). These results suggest that shifts in enzyme activities increased ligninase:cellulase ratio with time after biochar addition, limiting long-term soil C sequestration with biochar addition. Our work provides novel evidence to explain the diminished soil C sequestration with long-term biochar addition and suggests that earlier studies may have overestimated soil C sequestration with biochar addition by failing to consider the physiological acclimation of soil microorganisms over time.
生物炭改良是通过增强土壤碳（C）固存来应对气候变化最具前景的农业方法之一。微生物介导的分解过程对于土壤中固存碳的归宿和持久性至关重要，但其潜在机制尚不确定。在此，我们综合了来自全球五大洲130篇文章中关于生物炭添加（在从数周到数年的时间段内）对土壤碳降解酶活性影响的923条观测结果。我们的结果表明，生物炭添加使针对复杂酚类大分子的土壤木质素酶活性提高了7.1%，但使降解较简单多糖的纤维素酶活性降低了8.3%。这些酶活性的变化解释了在广泛的气候、土壤和实验条件下土壤碳固存变化的大部分差异，生物炭诱导的木质素酶：纤维素酶比率变化与土壤碳固存呈负相关。具体而言，短期（<1年）生物炭添加显著降低纤维素酶活性4.6%，并使土壤有机碳固存增加87.5%，而木质素酶活性和木质素酶：纤维素酶比率未观察到显著响应。然而，长期（≥1年）生物炭添加显著提高木质素酶活性5.2%，木质素酶：纤维素酶比率提高36.1%，导致土壤有机碳固存增加幅度较小（25.1%）。这些结果表明，生物炭添加后随着时间推移，酶活性变化导致木质素酶：纤维素酶比率增加，限制了生物炭添加对土壤碳的长期固存。我们的工作提供了新的证据来解释长期添加生物炭后土壤碳固存减少的现象，并表明早期研究可能因未考虑土壤微生物随时间的生理适应而高估了生物炭添加对土壤碳的固存作用。
