中文摘要：

Arbuscular mycorrhizal (AM ) 真菌形式 mutualistic symbioses 与最种种类并且在生态系统起重要作用。到温度的真菌改变的 AM 的反应的知识将在生态系统在全球气候变化情形下面改进我们 AM 真菌的社区的功能的理解。在 AM 真菌的社区上的不变的温暖的效果以前被调查了，但是对在 24-h 时期上的不均匀的温暖的回答从来没在自然生态系统被记录过。在这研究，我们检验了在完整的阶乘的真菌的社区设计包括在北中国在一个半干旱的大草原温暖的白天和夜间的 AM。白天并且 24-h 温暖，然而并非夜间温暖显著地增加了 AM 真菌的孢子密度。相反，任何一个都没在 AM 真菌的额外的激进的菌丝的密度上三温暖的政体有重要效果。AM 真菌的 161 个运作的分类单位(OTU ) 的一个总数被 18S rDNA 的 454 pyrosequencing 恢复。都显著地温暖的白天，夜间，和 24-h 增加了 AM 真菌的 OTU 丰富。一些 AM 真菌的 OTU 近白天，夜间或 24-h 温暖显示出重要偏爱。AM 真菌的社区作文被温暖的夜间，然而并非到白天并且 24-h 温暖显著地影响。我们发现加亮 AM 真菌的孢子密度和社区作文的不同回答到不均匀的温暖。这研究可能改进我们生态系统在一个半干旱的大草原生态系统在全球气候变化情形下面 AM 真菌的社区工作的理解。

英文摘要：

Arbuscular mycorrhizal （AM） fungi form mutualistic symbioses with most plant species and play important roles in ecosystems. Knowledge of the response of AM fungi to temperature change will improve our under- standing of the function of AM fungal community under global climate change scenarios in ecosystems. The effects of constant warming on AM fungal communities have been investigated previously, but responses to asymmetrical warming over 24-h periods have never been documented in natural ecosystems. In this study, we examined AM fungal communities in a full factorial design including day-time and night-time warming in a semiarid steppe in northern China. Day-time and 24-h warming, but not night-time warming, significantly increased AM fungal spore density. In contrast, none of the three warming regimes had a sig- nificant effect on AM fungal extra radical hyphal density. A total of 161 operational taxonomic units （OTUs） of AM fungi were recovered by 454 pyrosequencing of 18S rDNA. Day-time, night-time, and 24-h warming all significantly increased AM fungal OTU richness. Some AM fungal OTUs showed a significant bias toward day-time, night-time or 24-h warming. The AM fungal community composition was significantly affected by night-time warming, but not by day-time and 24-h warming. Our finding highlighted dif- ferent responses of AM fungal spore density and community composition to asymmetrical warming. This study might improve our understanding of ecosystem functioning of AM fungal community under global climate change scenarios in a semiarid steppe ecosystem.