Multiscale patterns of arbuscular mycorrhizal fungal abundance and diversity in semiarid shrublands

• We assessed AM fungal distributions at 3 spatial scales using 6 independent measures.
• Fungal indicators varied differentially at microsite, local, and regional scales.
• Unvegetated shrub interspaces contain abundant and diverse fungal communities.
• High alpha, beta, and gamma spore diversity and spatial autocorrelation was observed.
• Regional scale species patterns are driven by organic matter, climate and soil P.

The distribution of arbuscular mycorrhizal (AM) fungal abundance and diversity across multiple scales, and the factors that drive spatial patterns, remains largely unknown in arid ecosystems. We examined multiple measures of AM fungal abundance, as well as spore diversity and community composition, at microsite (1 m2), local (1 ha), and regional (5000 ha) scales in semiarid shrublands. At the microsite scale, hyphae, spores, and glomalin-related soil protein were more abundant underneath shrub canopies, but unvegetated shrub interspaces had similar amounts of viable propagules, spore diversity, and spore community composition compared to canopies. Significant local and regional scale variation in abundance, diversity, and community composition were correlated with variation in soil organic matter, climate, and soil phosphorus concentration. We observed high alpha, beta, and gamma spore diversity and significant spatial autocorrelation of communities. This study demonstrates how multiple indicators of Glomeromycotan abundance and diversity vary differentially in natural systems and how soil and climate factors are important drivers of spatial patterns.