Anthropogenic global change is increasing the severity and frequency of abiotic stresses such as drought that are likely to affect soil communities. Arbuscular mycorrhizal fungi (AMF) play important roles in many soil processes, so it is important to understand how drought affects AMF biodiversity. This is especially relevant in agricultural systems where crops rely on AMF associations for water and nutrient uptake, and where management decisions such as crop selection and fertilizer application may influence how the AMF community responds to drought. In this study, we examined the effects of reduced precipitation and nitrogen fertilization on AMF richness, community composition, and root and soil colonization in monocultures of two cultivars of switchgrass (Panicum virgatum) grown for bioenergy feedstock. We conducted a two-year field experiment using rain-out shelters to manipulate precipitation in mature stands of switchgrass growing in a long-term nitrogen fertilization (0 or 56 kg N ha⁻¹) experiment at the W.K. Kellogg Biological Station Long-Term Ecological Research site in Michigan, USA. We expected that AMF richness and colonization would decrease due to drought, as predicted by the stress exclusion hypothesis. Contrary to our expectations, we found that drought stress increased AMF species richness in fertilized plots by 15%; there was no effect of drought on AMF richness in unfertilized plots. Drought also significantly altered AMF community composition, primarily due to increases in Rhizophagus taxa abundance, and reduced AMF root colonization in switchgrass by 6%. We also found variation in AMF richness and colonization across switchgrass cultivars as well as sampling dates. The changes in AMF richness and composition that we observed in this study may have implications for perennial bioenergy feedstock selection and management as changes in AMF communities may feedback to affect host plants.

人为全球变化正在增加可能影响土壤群落的干旱等非生物胁迫的严重程度和频率。丛枝菌根真菌 (AMF) 在许多土壤过程中发挥重要作用，因此了解干旱如何影响 AMF 生物多样性非常重要。这在农业系统中尤其重要，在这些系统中，作物依赖 AMF 协会来吸收水分和养分，并且作物选择和施肥等管理决策可能会影响 AMF 社区对干旱的反应。在这项研究中，我们研究了减少降水和施氮对两种柳枝稷（Panicum virgatum) 为生物能源原料而种植。我们利用雨水了庇护所操纵的柳枝稷的成熟矗立在长期氮肥增长沉淀（0或56千克氮公顷进行了为期两年的田间试验^-1）实验在凯洛格生物站长期生态美国密歇根州的研究基地。正如压力排除假设所预测的那样，我们预计 AMF 丰富度和定植会因干旱而减少。与我们的预期相反，我们发现干旱胁迫使施肥地块中的 AMF 物种丰富度增加了 15%；在未施肥的地块中，干旱对 AMF 丰富度没有影响。干旱也显着改变了 AMF 群落组成，主要是由于根瘤菌的增加类群丰富，柳枝稷中 AMF 根的定植减少了 6%。我们还发现柳枝稷栽培品种的 AMF 丰富度和定植以及采样日期的变化。我们在本研究中观察到的 AMF 丰富度和组成的变化可能对多年生生物能源原料的选择和管理产生影响，因为 AMF 群落的变化可能会反馈影响寄主植物。