Zhang Yuting, Shen Hong, He Xinhua, Thomas Ben W, Lupwayi Newton Z, Hao Xiying, Thomas Matthew C, Shi Xiaojun
College of Resources and Environment, Southwest UniversityChongqing, China.
Agriculture and Agri-Food Canada, Lethbridge Research and Development CentreLethbridge, AB, Canada.
Front Microbiol. 2017 Jul 18;8:1325. doi: 10.3389/fmicb.2017.01325. eCollection 2017.
Application of chemical fertilizer or manure can affect soil microorganisms directly by supplying nutrients and indirectly by altering soil pH. However, it remains uncertain which effect mostly shapes microbial community structure. We determined soil bacterial diversity and community structure by 454 pyrosequencing the V1-V3 regions of 16S rRNA genes after 7-years (2007-2014) of applying chemical nitrogen, phosphorus and potassium (NPK) fertilizers, composted manure or their combination to acidic (pH 5.8), near-neutral (pH 6.8) or alkaline (pH 8.4) Eutric Regosol soil in a maize-vegetable rotation in southwest China. In alkaline soil, nutrient sources did not affect bacterial Operational Taxonomic Unit (OTU) richness or Shannon diversity index, despite higher available N, P, K, and soil organic carbon in fertilized than in unfertilized soil. In contrast, bacterial OTU richness and Shannon diversity index were significantly lower in acidic and near-neutral soils under NPK than under manure or their combination, which corresponded with changes in soil pH. Permutational multivariate analysis of variance showed that bacterial community structure was significantly affected across these three soils, but the PCoA ordination patterns indicated the effect was less distinct among nutrient sources in alkaline than in acidic and near-neural soils. Distance-based redundancy analysis showed that bacterial community structures were significantly altered by soil pH in acidic and near-neutral soils, but not by any soil chemical properties in alkaline soil. The relative abundance (%) of most bacterial phyla was higher in near-neutral than in acidic or alkaline soils. The most dominant phyla were Proteobacteria (24.6%), Actinobacteria (19.7%), Chloroflexi (15.3%) and Acidobacteria (12.6%); the medium dominant phyla were Bacterioidetes (5.3%), Planctomycetes (4.8%), Gemmatimonadetes (4.5%), Firmicutes (3.4%), Cyanobacteria (2.1%), Nitrospirae (1.8%), and candidate division TM7 (1.0%); the least abundant phyla were Verrucomicrobia (0.7%), Armatimonadetes (0.6%), candidate division WS3 (0.4%) and Fibrobacteres (0.3%). In addition, Cyanobacteria and candidate division TM7 were more abundant in acidic soil, whereas Gemmatimonadetes, Nitrospirae and candidate division WS3 were more abundant in alkaline soil. We conclude that after 7-years of fertilization, soil bacterial diversity and community structure were shaped more by changes in soil pH rather than the direct effect of nutrient addition.
施用化肥或粪肥可通过提供养分直接影响土壤微生物，也可通过改变土壤pH值间接影响土壤微生物。然而，哪种影响对微生物群落结构的塑造作用更大仍不确定。在中国西南部的玉米-蔬菜轮作体系中，我们对酸性（pH 5.8）、近中性（pH 6.8）或碱性（pH 8.4）的饱和土状淋溶土连续7年（2007 - 2014年）施用化学氮、磷、钾（NPK）肥料、堆肥或它们的组合后，通过对16S rRNA基因的V1 - V3区域进行454焦磷酸测序，测定了土壤细菌多样性和群落结构。在碱性土壤中，尽管施肥土壤中的有效氮、磷、钾和土壤有机碳含量高于未施肥土壤，但养分来源并未影响细菌操作分类单元（OTU）丰富度或香农多样性指数。相反，在酸性和近中性土壤中，NPK处理下的细菌OTU丰富度和香农多样性指数显著低于粪肥或它们的组合处理，这与土壤pH值的变化相对应。置换多元方差分析表明，这三种土壤中的细菌群落结构均受到显著影响，但主坐标分析排序模式表明，碱性土壤中养分来源的影响不如酸性和近中性土壤中明显。基于距离的冗余分析表明，酸性和近中性土壤中的细菌群落结构受土壤pH值显著影响，而碱性土壤中不受任何土壤化学性质的影响。大多数细菌门的相对丰度（%）在近中性土壤中高于酸性或碱性土壤。最主要的门是变形菌门（24.6%）、放线菌门（19.7%）、绿弯菌门（15.3%）和酸杆菌门（12.6%）；中等优势的门是拟杆菌门（5.3%）、浮霉菌门（4.8%）、芽单胞菌门（4.5%）、厚壁菌门（3.4%）、蓝细菌门（2.1%）、硝化螺旋菌门（1.8%）和候选分类单元TM7（1.0%）；最不丰富的门是疣微菌门（0.7%）、装甲菌门（0.6%）、候选分类单元WS3（0.4%）和纤维杆菌门（0.3%）。此外，蓝细菌门和候选分类单元TM7在酸性土壤中更为丰富，而芽单胞菌门、硝化螺旋菌门和候选分类单元WS3在碱性土壤中更为丰富。我们得出结论，施肥7年后，土壤细菌多样性和群落结构更多地是由土壤pH值的变化而非养分添加的直接影响所塑造。
