Arbuscular mycorrhizal fungi (AMF) represent important players in the structure and function of many ecosystems. Yet, we learn about their roles mostly from greenhouse-based experiments, with results subjected to cultivation bias. This study explores multiple aspects of this bias and separates the effect of increased nutrient availability from other cultivation specifics. For 15 grassland plant species from two functional groups (C3 grasses vs dicotyledonous forbs), we compared AMF communities of adults collected from non-manipulated vegetation with those in plants grown in a greenhouse. Nutrient availability was comparable to field conditions or experimentally elevated. We evaluated changes in AMF community composition, diversity, root colonisation, and the averages of functional traits characterising hyphal soil exploration. Additionally, we use the data from the greenhouse experiment to propose a new plant functional trait—the change of AMF colonisation in response to nutrient surplus. The AMF community differed profoundly between field-collected and greenhouse-grown plants, with a larger change of its composition in grass species, and AMF community composition in grasses also responded more to fertilisation than in forbs. Taxonomic and phylogenetic diversity declined more in forbs under cultivation (particularly with elevated nutrients), because in their roots, the AMF taxa from families other than Glomeraceae largely disappeared. A decline in AMF colonisation was not caused by greenhouse cultivation itself but selectively by the elevation of nutrient availability, particularly in grass host species. We demonstrate that the extent of decrease in AMF colonisation with elevated nutrients is a useful plant functional trait explaining an observed response of the plant community to manipulation.

丛枝菌根真菌 (AMF) 是许多生态系统结构和功能的重要参与者。然而，我们主要从基于温室的实验中了解它们的作用，结果受栽培偏差的影响。本研究探讨了这种偏差的多个方面，并将增加养分可用性的影响与其他栽培细节区分开来。对于来自两个功能组（C3 禾本科植物与双子叶植物）的 15 种草原植物物种，我们比较了从非操纵植被收集的成虫 AMF 群落与温室中生长的植物群落。养分可用性与田间条件相当或通过实验提高。我们评估了 AMF 群落组成、多样性、根系定植和表征菌丝土壤勘探的功能性状平均值的变化。此外，我们使用温室实验的数据提出了一种新的植物功能性状——AMF 定植响应养分过剩的变化。田间采集的植物和温室种植的植物之间的AMF群落差异很大，草种中其AMF群落组成的变化更大，草中的AMF群落组成对施肥的反应也比对Forb的反应更大。栽培中的杂种（特别是营养物质增加）的分类学和系统发育多样性下降更多，因为在它们的根部，来自除Glomeraceae 以外的科的AMF 分类群基本上消失了。AMF 定植的减少不是由温室栽培本身引起的，而是由养分可用性的增加引起的，特别是在草宿主物种中。