中国东北黑土土壤剖面微生物群落碳源代谢特征

Metabolic characteristics of the microbial community on the basis of carbon source in black soil profiles in northeastern China

利用Biolog Eco微平板培养法,对中国科学院海伦农田生态系统国家野外科学观测研究站农田(CL)、恢复草地(GL)和人工林地(FL)土壤剖面不同深度土壤中微生物群落碳源代谢特征进行研究。理化性质结果显示,有机碳、全氮和碱解氮含量随深度增加逐渐减少,p H则是上层土壤低于底层。可培养微生物数量从表层(0—20 cm)到底层(180—200 cm)逐渐减少,在表层(0—20 cm)3种可培养微生物数量均为草地>农田>林地。可培养微生物主要生活在近地表0—60 cm土层中,在60—200cm土层中3种利用方式下可培养细菌、真菌和放线菌数量基本相同。Biolog结果显示,在0—40 cm土层中微生物群落活性最大,底层(180—200 cm)土壤微生物群落活性最小。3种利用方式剖面微生物群落Shannon多样性指数和碳源利用数量从表层到底层逐渐减少,并且与SOC和TN呈极显著正相关关系(P<0.05)。与农田相比恢复草地和人工林地剖面20—40 cm土层中微生物群落对各类碳源的利用强度都较高,说明没有农业机械作业的植被自然生长条件下根系会打破原来农田中的犁底层,促进表层(0—20 cm)以下微生物群落活性。碳源利用率和主成分分析结果表明长期不同植被覆盖已经改变了剖面微生物群落碳源代谢特征,而且根系已经影响到100 cm的微生物群落,但还没有影响到180—200cm中的微生物群落。

Using long-term field experiment of different ecosystems established at the Hailun State Key Experimental Station of Agroecology, Chinese Academy of Sciences, soil profiles down to the parent material layer （200 cm） were collected to investigate microbial metabolic characteristics of the carbon source by using the Biolog ECO micro-plate technique. The field treatments included three different ecosystems： Crop Land （CL）, Grass Land （GL）, and Forest Land （FL）. The results showed that soil organic carbon （SOC）, total nitrogen （TN） , and effective nitrogen （EN） decreased with soil depth; soil pH increased with soil depth, and it was lower in the surface layer （0--20 cm） than in the bottom layer （180--200 cm）. The number of cultivable microorganisms （bacteria, fungi, and actinomyeetes） gradually decreased with soil depth; the cultivable microorganisms mainly lived in the top 0--60 cm soil layer. The numbers of the three types of cultivable microorganisms decreased in the order of GL 〉 CL 〉 FL at 0--20 cm soil depth, and the numbers were almost the same in the three ecosystems in the 60--200 cm soil layer. Activities of the soil microbial community were the highest at 0--40 cm soil depth and decreased with soil depth; the lowest value was observed in the 200 cm soil layer. Similar to SOC and TN, the Shannon diversity index and carbon source utilization gradually decreased with soil depth and showed a positive correlation with SOC and TN （P 〈 0.05）. Compared to CL, carbon use efficiency of the soil microbial community improved at subsurface soil depth （ 20--40 cm） in GL and FL. This demonstrated that the roots of the vegetation could break the plow pan in GL and FL soils without any tillage activities and promote the activities of the soil microbial community below the surface soil layers. Principal component analysis of the utilization intensity of six types of carbon sources showed that the different long-term ecosystems with different vegetation types had changed the carbon utilization intensity of the soil microbial community in the soil profiles. The roots of the vegetation or crops had great influence on the soil microbial community to 100 cm depth, but not to 200 cm depth.