基于梯度稀释法分析细菌多样性对土壤碳代谢的影响

为探究土壤微生物多样性对土壤碳代谢过程的影响,利用梯度稀释法(处理D1、D3和D5分别为稀释10-1、10-3和10-5倍)改变土壤样品中原始土壤微生物群落的多样性,以探究土壤微生物群落多样性减少对土壤碳代谢的影响。进行为期6周的预培养实验,以消除梯度稀释法对土壤样品中微生物群落丰度的影响,并通过Q-PCR和高通量测序测定预培养结束后3种土壤样品中细菌丰度及其基因多样性指数(ACE、Chao1、Shannon),以验证预培养实验结果。后加入等量葡萄糖(0.5g/100g干土)继续培养,并于培养期间测定3种处理土壤的碳矿化速率,进行biolog ECO板实验,分析计算各土壤样品中细菌的功能多样性指数(Shannon指数(H)、Simpson指数(D)、McIntosh指数(U))及碳源代谢强度。结果表明:(1)3种处理土壤样品碳矿化速率及累积碳矿化量大小排序为:D1> D3> D5,且D1与D3、D5处理均有显著差异(P<0.05)。(2)D1处理下土壤样品中微生物群落的孔平均颜色变化率(AWCD)、功能多样性指数(Shannon指数(H)、McIntosh指数(U))均显著高于D3、D5处理(P<0.05)。(3)对31种碳源吸光度做主成分分析(PCA)分析,发现3种稀释处理下土壤样品的碳源利用模式存在差异,且D1处理下的土壤微生物群落对碳源的代谢功能大于D3、D5处理。因此,该研究表明土壤微生物多样性的减少会降低土壤的碳矿化速率及其碳源代谢强度,对土壤碳代谢过程产生一定程度的不利影响。

Effects of soil bacterial diversity on soil carbon metabolism based on gradient dilution method

In order to investigate the relationship between soil microbial diversity and soil carbon metabolism, this study used gradient dilution method to modify the diversity of the original soil microbial community(the dilution of 10^-1, 10^-3 and 10^-5 times for treatments of D1, D3 and D5, respectively). Six weeks of pre-culture experiment was carried out to eliminate the effects of gradient dilution on microbial community abundance in soils. To evaluate the results of pre-culture experiments, the bacterial abundance and gene diversity index (ACE, Chao1 and Shannon) were determined by the Q-PCR and high-throughput sequencing, respectively. Thereafter, the same amount of glucose (0.5 g/100 g dry soil) was added in the culture, and the carbon mineralization rates of the three treated soils were measured during the incubation period. The Biolog ECO plate experiment was performed to analyze the functional diversity index (Shannon Index (H), Simpson index (D), and McIntosh index (U)) and carbon source metabolic intensity of bacteria in each soil sample. The results showed that the soil carbon mineralization rates and cumulative carbon mineralization were the greatest in D1 treatment, followed by D3 and D5. The average well color development (AWCD), H and U were significantly higher under D1 treatment than those under D3 and D5 treatments (P<0.05). Principal component analysis for 31 kinds of carbon sources also indicated that the patterns of carbon source utilization of the three treatments were different, and the effect of soil microbial community on carbon source utilization under D1 was more significant than that under D3 and D5 (P<0.05). Taken together, this study showed that the decreases of soil microbial diversity would alter the soil carbon metabolic intensity and mineralization processes.