Transient negative biochar effects on plant growth are strongest after microbial species loss

Biochar has been explored as an organic amendment to improve soil quality and benefit plant growth. The overall positive effects of biochar on crop yields are generally attributed to abiotic changes, while the alternative causal pathway via changes in soil biota is unexplored. We compared plant growth effects of legumes in sterile soil inoculated with dilutions of soil and soil microbial suspensions to determine the direct effects of biochar-induced changes in soil biota on plant growth. Suspensions and soil were from soil amended with biochar and soil without biochar. By comparing consecutive plant growth phases on the same inoculated soils, we also determined the temporal effects of soil biota from biochar-amended and control soils. Biota from biochar-amended soil was less beneficial for Medicago sativa growth, especially with small amounts of inocula. Flowering was delayed in the presence of biota from biochar plots. Inoculum with either soil or soil suspension gave similar results f...生物炭（Biochar）作为一类有机土壤改良剂，已被广泛研究用于改善土壤质量并促进植物生长。当前普遍认为，生物炭对作物产量的整体积极效应源于非生物环境改变，而其通过调控土壤生物区系（soil biota）发挥作用的潜在因果路径尚未得到探索。为明确生物炭诱导的土壤生物区系改变对植物生长的直接效应，本研究将豆科植物种植于经土壤及土壤微生物悬浮液稀释物接种的无菌土壤中开展对比分析。所用悬浮液及土壤均取自施加生物炭的处理组与未施加生物炭的对照组土壤。通过在同一接种土壤上连续开展多轮植物生长周期实验，本研究还解析了源自生物炭处理组与对照组土壤的生物区系的时序效应。结果显示，源自生物炭处理组土壤的生物区系对紫花苜蓿（Medicago sativa）生长的促进效果更弱，尤其当接种物用量较少时该效应更为显著。接种生物炭处理组土壤生物区系的植株，开花时间有所延迟。无论是以土壤还是土壤悬浮液作为接种物，均得到了相似的实验结果[原文未完]