Abstract Microbial functional genes can reflect the nutrient cycle activities in soil, because they encode various enzymes involved in the material cycle. Therefore, the gene abundance variation can reveal the impact of interference on the material cycle of grassland. To study the cycle of carbon (C), nitrogen (N) and phosphorus (P) between plant and soil in grassland under different grazing regimes, we investigated the soil microbial functional genes related to C, N, and P cycling by high-throughput quantitative PCR and 16S rRNA-based Illumina sequencing analysis under grazing exclusion (GE), rotational grazing (RG), and continuous grazing (CG) in alpine meadow of the Qinghai-Tibetan Plateau, where climate is characterized by little rain and low temperature, and grassland is very sensitive to grazing. The results showed at the early grazing period, C fixtion (rbcL, korA, and frdA) and lignin degradation (abfA, xylA, exg, lig, exoPG, chiA, and glx) processes were slower under GE; CH4 metabolism (mcrA) was faster under CG; RG and CG improved the denitrification process (narG); RG slowed down organic-P mineralization (phoD). At the late grazing period, C fixation (accA and frdA) and degradation (mnp, apu, and amyA) processes were slower under GE; CH4 metabolism (pmoA and mxa) was faster under CG; RG and CG improved the ammonia-oxidizing (amoA2), nitrification (hao), and denitrification (nirS3 and nirK1) processes. The majority of the genes involved in C, N, and P cycling decreased, the C, N and P content in plant leaf decreased, while that of soil increased from early to late grazing period. No matter grazing or not, there were negative relationships between genes and soil nutrients, and positive relationships between genes and plant nutrients, implying a trade-off between plant nutrients and soil nutrients along the grazing time. The genes responsible for regulating C and N cycling were increased under grazing, implying that reasonable grazing is beneficial to the nutrients cycling of grassland.

中文翻译：

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青藏高原高寒草甸放牧促进土壤微生物功能基因调控碳氮循环

摘要 微生物功能基因可以反映土壤养分循环活动，因为它们编码参与物质循环的各种酶。因此，基因丰度变异可以揭示干扰对草地物质循环的影响。为了研究不同放牧条件下草地植物与土壤之间碳（C）、氮（N）和磷（P）的循环，我们通过高通量研究了与C、N、P循环相关的土壤微生物功能基因在以少雨、低温为特征的青藏高原高寒草甸放牧（GE）、轮牧（RG）和连续放牧（CG）条件下的定量PCR和基于16S rRNA的Illumina测序分析，草原对放牧非常敏感。结果表明，在早期放牧期间，GE 下 C 固定（rbcL、korA 和 frdA）和木质素降解（abfA、xylA、exg、lig、exoPG、chiA 和 glx）过程较慢；CH4 代谢 (mcrA) 在 CG 下更快；RG和CG改进了反硝化过程（narG）；RG 减慢了有机磷矿化 (phoD)。在放牧后期，GE 下的碳固定（accA 和 frdA）和降解（mnp、apu 和 amyA）过程较慢；CH4 代谢（pmoA 和 mxa）在 CG 下更快；RG 和 CG 改进了氨氧化 (amoA2)、硝化 (hao) 和反硝化 (nirS3 和 nirK1) 过程。大部分参与C、N、P循环的基因减少，植株叶片C、N、P含量降低，而土壤C、N、P含量从放牧初期到后期增加。不管放牧与否，基因与土壤养分之间存在负相关关系，而基因与植物养分之间存在正相关关系，这意味着在放牧期间植物养分和土壤养分之间存在权衡。放牧条件下调控碳氮循环的基因增加，表明合理放牧有利于草地养分循环。