接种菌根真菌和氮添加处理对樟子松苗木根际微生态环境的影响

通过研究接种菌根真菌和N添加处理对植物根际土壤胞外酶及其计量特征，以及微生物养分限制的影响，从而探讨全球N沉降背景下菌根真菌对根际微生态环境的调控机制。以1年生樟子松的盆栽菌根苗（简称+M，混合接菌处理）和非菌根苗（简称-M，未接菌处理）为对象，设置4个N添加处理:不施N（0N，0 kg·hm^-2·a^-1）、低氮（LN，15 kg·hm^-2·a^-1）、中氮（MN，30 kg·hm^-2·a^-1）、高氮（HN，60 kg·hm^-2·a^-1）。对比分析接菌和N添加处理对樟子松苗木根际土壤速效养分和胞外酶活性及其计量特征的影响，探究菌根真菌对微生物养分限制调控规律。结果表明:1）不同接菌处理下，随N添加量增加，土壤中碱解N均呈增加的趋势。HN处理下，菌根苗根际土壤有效磷达到最大。2）LN、MN处理下，菌根苗根际土LAP、NAG和ALP酶活性均显著高于非菌根苗。3）MN、HN处理下，菌根苗根际土壤中微生物碳限制和磷限制较非菌根苗均显著降低。4）通过PLS-PM路径模型分析发现，接菌处理正效应作用于根际土壤微生物养分限制。综上，N添加改变了根际土壤N平衡，菌根真菌有效调控N添加下根际微生态环境的稳定性，降低苗木根际微生物的碳和磷限制。

Responses of the Rhizosphere Soil Microecological Environment of Pinus sylvestris var.mongolica to Inoculation and Nitrogen Addition Treatments

In order to explore the regulation mechanisms of mycorrhizal fungi for rhizosphere microecological environment under the background of global N deposition,the response of plant rhizosphere soil exoenzymes and its stoichiometry characteristics and microbial nutrient limitation to mycorrhizal fungus inoculation and nitrogen (N) addition were studied.The 1-year-old Pinus sylvestris var.mongolica mycorrhizal (+M,mixed inoculated with 8 ectomycorrhizal fungi) and non-mycorrhizal seedlings (-M,no inoculation) in pots were used as research objects.Four N addition treatments were set,including no N (0 N，0),low N (LN,30),medium N (MN,60),high N (HN,90 kg·hm^-2·year^-1).The available nutrients and ecoenzyme activities and its ecoenzymatic stoichiometry of P.sylvestris var.mongolica rhizosphere soils were analyzed under inoculation and N addition treatments to explore the regulation rule of mycorrhizal fungi to microbial nutrient limitation.1) The soil available N increased with the increase of N addition under different inoculation treatments.The soil available phosphorus (P) of mycorrhizal seedlings was the maximum under HN treatment.2) The activities of LAP,NAG and ALP in the rhizospheres of mycorrhizal seedlings were significantly higher than those of non-mycorrhizal seedlings under LN and MN treatments,respectively.3) The microbial carbon (C) and P limitation of mycorrhizal seedlings were significantly lower than those of non-mycorrhizal seedlings under MN and HN treatments,respectively.4) The partial least squares path modelling (PLS-PM) indicated that inoculation treatment had a positive effect on microbial nutrient limitation in the rhizosphere soil.Thus,N addition changed the N balance of the rhizosphere soil,and the mycorrhizal fungi regulated the stability of rhizosphere microecological environment under nitrogen addition effectively,and reduced the microbial C and P limitation rhizosphere in the rhizospheres of seedlings.