攀西高原不同轮作制度下土壤固氮微生物nifH基因多样性与群落结构特征

Effect of crop rotation system on diversity and community structure of soil microorganisms with nifH gene in Panxi Plateau, China

摘要:

【背景】关于高原生境轮作制度对土壤固氮微生物群落组成及多样性的影响研究尚少。【目的】深入认识攀西高原不同轮作制度对农田土壤肥力及土壤固氮微生物nifH基因群落结构与多样性的影响，以期建立合理的轮作制度。【方法】以凉山州冕宁县不同作物轮作制度[包括光叶紫花苕-烤烟(分轮作15年和20年两种，分别为G1和G2)、苦荞-烤烟(KQ)、大麦-烤烟(DM)和撂荒(CK)]的土壤为研究对象，通过化学分析和Illumina MiSeq技术，对土壤理化性质、土壤固氮微生物nifH基因多样性及群落组成进行分析。【结果】撂荒土壤全氮、铵态氮、硝态氮、有机碳和含水量最显著(P<0.05)。KQ轮作下土壤有效磷和速效钾分别提高了43.0%和2.60%，而DM轮作下的土壤理化性质均下降。土壤固氮酶活以撂荒土壤最高，G2轮作最低。土壤固氮微生物nifH基因多样性以G1轮作最高、G2轮作最低，门水平上以变形菌门(Proteobacteria)是优势共有nifH基因类群，相对丰度占群落的63.0%-92.4%；属水平上，偶氮氢单胞菌属(Azohydromonas)是不同轮作制度下的优势物种，慢生根瘤属(Bradyrhizobium)是撂荒土壤中的优势物种。【结论】冗余分析发现，土壤pH和含水量是驱动土壤固氮微生物nifH基因的群落组成的关键因子。本研究表明不同轮作制度可以明显改变土壤肥力状况和固氮微生物nifH基因群落组成，其中以光叶紫花苕-烤烟轮作15年的影响最明显，可以提高土壤养分含量，增加土壤固氮微生物nifH基因多样性。

Abstract:

[Background] A few studies of the effect of rotation system on the community structure and diversity of soil nitrogen-fixing microorganisms on plateau are available. [Objective] To clarify the effect of rotation system on farmland soil fertility and diversity and community structure of soil microorganisms with nifH gene on Panxi Plateau and screen a reasonable rotation system. [Methods] Soil samples were collected from five crop rotation systems: 15-year Vicia villosa Roth-flue-cured tobacco rotation (G1), 20-year V. villosa -flue-cured tobacco rotation (G2), tartary buckwheat (Fagopyrum tataricum)-flue-cured tobacco rotation (KQ), barley (Hordeum vulgare L.)-flue-cured tobacco rotation (DM), and abandoned soil (CK) in Mianning county, Liangshan prefecture. Through chemical analysis and high-throughput sequencing of nifH, soil physico-chemical properties and community structure and diversity of soil nitrogen-fixing microorganisms were analyzed. [Results] The total nitrogen content, ammonium nitrogen content, nitrate nitrogen content, organic carbon content, and water content were the highest in the CK (P <0.05) and the pH value was below 7 in all rotation systems. Under KQ, content of soil available phosphorus and available potassium was 43.0% and 2.60% higher, respectively. Soil physico-chemical parameters were lower under DM rotation than in CK. Soil nitrogenase activity was highest in CK and lowest under G2. The diversity of nitrogen-fixing microorganisms was the highest under G1 and lowest under G2. At the phylum level, the relative abundance of Proteobacteria was the highest, accounting for 63.0%-92.4% of the total abundance. At genus level, Azohydromonas dominated the soils under crop rotation and Bradyrhizobium was most abundant in CK. Redundancy analysis revealed that soil pH and water content were the key factors driving the composition of soil nitrogen-fixing microorganisms. [Conclusion] Rotation systems obviously changed the soil fertility and the composition of nifH gene community, particularly the G1 which improved soil nutrient content and diversity of soil nitrogen-fixing microorganisms.