Astraeus, commonly referred to as the hygroscopic earthstar, barometer earthstar, or false earthstar, is an ectomycorrhizal fungus that is widely consumed in Asia and forms symbiotic associations with tree species belonging to the families Dipterocarpaceae and Pinaceae, among others. This genus is typically distributed in dry dipterocarp forests in northern and northeastern Thailand. However, knowledge on the composition and diversity of fungal communities in areas where Astraeus occurs remains limited. Therefore, this study aimed: (i) to investigate the composition and diversity of soil fungal communities associated with Astraeus across five forest types in Thailand, and (ii) to identify the environmental factors influencing the occurrence of Astraeus species by using NGS (Next-generation sequencing) amplicon sequencing, which targets the Internal Transcribed Spacer 1 (ITS1) region of the rRNA gene. Overall, the results revealed that Astraeus distribution was only in two forest types, namely deciduous dipterocarp forest (DDF) and pine-deciduous dipterocarp forest (PDDF). These forests harbored abundant fungal communities, particularly ectomycorrhizal fungi. Forests where Astraeus was detected (DDF and PDDF) exhibited distinct fungal community composition and diversity compared with forests without Astraeus (dry evergreen forest (DEF), lower montane pine-oak forest (LMPF), and tropical evergreen rain forest (TEF)). Soil properties analysis indicated that Astraeus tends to prefer sandy or sandy loam soils, while showing a negative association with clay soils. These findings emphasize fungal community diversity shape forest ecosystems and the role of the presence or absence of Astraeus. The occurrence of Astraeus is influenced by forest type and soil properties.

Astraeus is an ectomycorrhizal fungus that forms symbiotic associations with trees of the families Dipterocarpaceae and Pinaceae and is typically distributed in dry dipterocarp forests in northern and northeastern Thailand. However, knowledge of the composition and diversity of fungal communities in areas where Astraeus occurs remains limited. Therefore, this study investigated soil fungal community composition and diversity associated with Astraeus in five Thai forest types and identified key environmental drivers using NGS amplicon sequencing targeting the ITS1 region of the rRNA gene. These forests harbored abundant fungal communities, particularly ectomycorrhizal fungi. Forests where Astraeus was detected (DDF and PDDF) exhibited distinct fungal community composition and diversity compared with those without Astraeus (dry evergreen forest (DEF), lower montane pine–oak forest (LMPF), and tropical evergreen rain forest (TEF)). Soil properties, particularly clay content, differed significantly between Astraeus-detected and Astraeus-not-detected soils; although there was a tendency toward higher sand content in Astraeus-detected soils, this was not statistically significant. Overall, the occurrence of Astraeus is primarily driven by forest type and soil properties, highlighting its role in forest fungal diversity.