Objective] The objective of this paper is to study the influences of biochar derived from tobacco stems and mulberry branches on red soil aggregate stability and microbial community structure abundance, provide high quality modified materials for cultivating structural stability of soil aggregate.[Method] Soil samples were incubated for four months by adding four different rates (1%, 2%, 4% and 6%) of tobacco stems biochar (Y1, Y2, Y4, and Y6) and mulberry branches biochar (S1, S2, S4, and S6), and non-biochar control (CK). Then, sieving methods were used to detect the distribution of aggregates (>2, 1-2, 0.5-1, 0.25-0.5,0.25 mm soil aggregates:R0.25 and percentage of aggregate disruption:PAD). The numbers of soil fungi, bacteria and actinomycetes were measured by microbial dilution plate counting cultivation method.[Result] Water-stable aggregates were changed significantly after biochar additions. Compared with CK, Y4and S4 treatments significantly increased the 0.5-1 mm fractions by 61.0% and 43.6%; Y1 and S2 treatments significantly increased the 0.25-0.5 mm fractions by 40.8% and 27.1%, while the<0.25 mm aggregates reduced by 9.2% and 8.4%. Compared to CK, both Y2 and S2 enhanced the values ofMWD more than 10% and Y1 and S2 treatments increasedR0.25by 31.4% and 28.7%, respectively. Accordingly, the PDAin the Y6 and S6 treatments were decreased by 22.0% and 18.2%, respectively. Furthermore, biochar additions significantly increased the soil fungi, actinomycetes and bacteria community. The Y4 and S4 treatments resulted in a richest amount of microbial community. In the tobacco stems treatments, a significant correlation existed between the aggregate stability index (MWD,R0.25) with the fungi (R2=0.89,P=0.030;R2=0.86,P=0.039) and actinomycetes (R2=0.87,P=0.035;R2=0.90, P=0.021). Moreover,PAD significantly reduced with the increased fungi (P<0.01), and actinomycetes and bacteria (P<0.05).[Conclusion]The biochar derived from tobacco stems and mulberry branches enhanced the formation of macro-aggregate (0.25-1 mm), soil aggregates stability and abundance of soil microbial communities. The effect of tobacco stems biochar was better than that of mulberry branches, and the appropriate application is 2%-4%.%【目的】研究烟秆炭和桑条炭对红壤团聚体结构稳定性和微生物群落丰度的影响，为培育结构稳定的红壤团聚体提供优质改良材料。【方法】通过室内培养试验，添加1%、2%、4%、6%土壤质量的烟秆炭（Y1、Y2、Y4、Y6）和桑条炭（S1、S2、S4、S6），对照（CK）无添加，4个月后采用筛分法对土壤团聚体结构（＜0.25、0.25—0.5、0.5—1、1—2、＞2 mm团聚体粒级分布，平均重量直径（MWD），＞0.25 mm团聚体含量（R0.25）、团聚体破坏率（PAD））进行分析，采用微生物稀释平板法测定土壤真菌、放线菌、细菌数量。【结果】施入生物质炭后，水稳性团聚体发生显著变化。Y4和S4处理下，0.5—1 mm团聚体较对照显著增加61.0%和43.6%；Y1和S2处理，0.25—0.5 mm团聚体较对照显著增加40.8%和27.1%，＜0.25 mm的团聚体含量较对照显著降低9.2%和8.4%；Y2和S2处理的MWD表现一致，均较对照显著提高10%以上，Y1和S2处理R0.25较对照显著提高31.4%和28.7%，Y6和S6处理PAD显著降低22.0%和18.2%；土壤真菌、放线菌、细菌数量均显著增加，Y4和S4处理微生物群落最丰富；烟秆炭处理下，土壤团聚体稳定性指标（MWD、R0.25）和土壤微生物之间存在显著和极显著相关性，尤其与真菌(R2=0.89, P=0.030；R2=0.86, P=0.039)和放线菌(R2=0.87, P=0.035； R2=0.90, P=0.021)相关性更显著；PAD随真菌数量的增加而极显著降低(P＜0.01），随放线菌和细菌数量的增加而显著降低（P＜0.05）。【结论】烟秆炭和桑条炭均能促进大团聚体（0.25—1 mm）的形成，提高红壤团聚体结构稳定性，增加土壤微生物群落丰度，烟秆炭改良效果优于桑条炭，以2%—4%添加量为宜。
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