磷供应对玉米根际微生物碳源利用和功能多样性的影响

磷有效性能够改变根分泌物的组成和数量,调节土壤微生物的群落结构和多样性,但磷添加如何影响土壤微生物碳源利用和功能多样性尚不清楚。本研究通过盆栽土培试验,设置2个磷处理[低磷5.7 mg(P)?kg?1和高磷200 mg(P)?kg?1],以生长35 d的玉米根际土壤为研究对象,采用Biolog微平板法,分别在培养后240 h内每隔24 h检测具有31种不同碳源的微孔溶液颜色变化,揭示磷供应对玉米根际微生物碳源利用模式和功能多样性的影响。结果表明:随着培养时间的延长,土壤微生物对土壤碳源的利用呈现增加的趋势,直至碳源消耗殆尽;高磷供应显著增加了玉米根际土壤微生物群落平均颜色变化率(average well color development,AWCD),提高了对糖类及其衍生物、氨基酸和代谢产物的利用,但没有显著提高对脂肪酸和脂类的利用;在培养前72 h内,高磷供应显著增加了玉米根际微生物多样性指数、优势度指数和均匀度指数,但培养72 h后,磷供应对其没有显著的影响。主成分分析结果表明,提取的前3个主成分解释了75.15%的碳源利用,高磷和低磷处理具有显著不同的土壤微生物碳源利用模式。总之,糖类及其衍生物、氨基酸和代谢产物是玉米根际土壤微生物利用的主要碳源,短期磷添加能够显著增加土壤微生物对碳源的利用,在一定程度上能够提高土壤微生物群落功能多样性。

Effects of phosphorus supply on microbial carbon source utilization and functional diversity of maize rhizosphere

Phosphorus (P) is a key nutrient which influences the growth, development and yield of crops. P availability can regulate soil microbial community structure and diversity by altering the quantity and components of root exudates. Whether P addition increases carbon resources utilization and functional diversity of soil microorganisms remains highly debatable. Also how P addition affects carbon resources utilization and functional diversity of soil microorganisms is not fully understood. In this study, a pot soil culture experiment with 2 P application treatments [low P of 5.7 mg(P)kg^-1(soil) and high P of 200 mg(P)kg^-1(soil)] was carried out to investigate the effect of P on carbon resources utilization and functional diversity of microorganisms in maize rhizosphere soil. After 35 d of growth, maize rhizosphere soil was collected using the nylon mesh method under 2 P treatments. The Biolog microplate technique was used to examine the color change of micro-well solutions containing 31 carbon sources every 24 h for consecutively 240 h. The results showed that with prolonged culture time, the utilization of 31 types of carbon sources by soil microorganisms obviously increased until the carbon sources in the micro-well solution were exhausted. High P treatment significantly increased average well color development (AWCD) and improved the utilization of carbohydrate carbon and its derivatives, amino acids and metabolites, but not affected the utilization of fatty acids and lipids. Functional diversity of soil microorganisms in maize rhizosphere soil was regulated by P availability, which depended largely on culturing time. During 72 h cultivation, high P treatment significantly increased the diversity index, dominance index and evenness index of soil microorganisms. However, after 72 h of cultivation, high P treatment had no significant effect on soil microorganism diversity. Based on principal component analysis (PCA), extracted first 3 components explained 75.15% of carbon sources utilization and separated 2 categories based on P treatments. A total of 23 carbon sources was correlated with PC1, 8 correlated with PC2 and 3 correlated with PC3. Multivariate analysis showed that the pattern of carbon sources utilization of soil microorganisms under high P supply was significantly different from that under low P supply (Hotelling trace = 2.485, F = 62.95, P < 0.001). In conclusion, carbohydrate and the derivatives, amino acids and metabolites were the major carbon sources utilized by soil microorganisms in maize rhizosphere soil. P addition significantly increased carbon sources utilization by soil microorganisms. To some extent, it also improved soil microbial functional diversity in maize rhizosphere soil.