Lv Fenglian, Xue Sha, Wang Guoliang, Zhang Chao
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi, China.
Institute of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi, China.
PLoS One. 2017 Feb 24;12(2):e0172382. doi: 10.1371/journal.pone.0172382. eCollection 2017.
Atmospheric nitrogen (N) deposition profoundly alters the soil microbial communities and will thus affect nutrient cycles. The effects of N availability on microbial community, however, are not clear. We used PLFA analysis to evaluate the effects of a gradient of N addition (0, 2.8, 5.6, 11.2, and 22.4 g N m-2 y-1) for three years on the rhizospheric microbial community of Pinus tabuliformis seedlings. The main factors influencing the community were quantified using structural equation modelling and redundancy analysis. At the microbial-community level, N addition increased the total phospholipid fatty acids content by increasing the dissolved organic carbon (DOC) and root biomass. Increases in soil microbial biomass carbon and N, however, was attributed to the increased DOC, N content and decreased pH. At the microbial-groups level, Fungal, arbuscular mycorrhizal fungal (AMF), gram-positive bacterial (GP) abundances and the GP:GN ratio first increased and then decreased with N addition. Nitrogen addition increased the abundances of bacteria, fungi, and actinomycetes mainly by increasing the DOC content and decreasing root biomass. Additionally, the decrease of pH and ammonium N caused by N addition increased the fungal abundances and reduced actinomycete abundances, respectively. Nitrogen addition shifted the rhizospheric microbial community mainly by altering the DOC content and root biomass. The current rate of N deposition (2.5 g N m-2 y-1) benefits plant growth and increases the abundances of fungi, arbuscular mycorrhizal fungi, GP, actinomycetes and the GP:GN ratio.
大气氮（N）沉降深刻改变土壤微生物群落，进而影响养分循环。然而，氮有效性对微生物群落的影响尚不清楚。我们采用磷脂脂肪酸（PLFA）分析方法，评估了连续三年施加不同梯度氮（0、2.8、5.6、11.2和22.4 g N m-2 y-1）对油松幼苗根际微生物群落的影响。利用结构方程模型和冗余分析对影响群落的主要因素进行了量化。在微生物群落水平上，施氮通过增加溶解有机碳（DOC）和根系生物量提高了总磷脂脂肪酸含量。然而，土壤微生物生物量碳和氮的增加归因于DOC、氮含量的增加以及pH值的降低。在微生物类群水平上，真菌、丛枝菌根真菌（AMF）、革兰氏阳性菌（GP）丰度以及GP:GN比值随施氮量增加先升高后降低。施氮主要通过增加DOC含量和降低根系生物量来提高细菌、真菌和放线菌的丰度。此外，施氮导致的pH值降低和铵态氮增加分别提高了真菌丰度和降低了放线菌丰度。施氮主要通过改变DOC含量和根系生物量来改变根际微生物群落。当前的氮沉降速率（2.5 g N m-2 y-1）有利于植物生长，并增加了真菌、丛枝菌根真菌、GP、放线菌的丰度以及GP:GN比值。
