AMF Propagule Status Beneath Pioneer Vegetation After Two Decades of Tropical Quarry Restoration

Arbuscular mycorrhizal fungi (AMF) support plant establishment and soil recovery in degraded lands, yet their long-term associations with vegetation in restored quarries remain poorly understood. This study quantified AMF spore density and genus-level occurrence in pioneer-plant rhizospheres at a cement quarry revegetated more than two decades earlier. AMF infective potential was assessed using Pueraria javanica trap cultures. Relationships among AMF attributes, vegetation strata, rhizosphere flavonoids, and soil chemical properties were evaluated using mixed-effects, correlation, and multivariate analyses. Trap-culture colonization was high across tree-, shrub-, and herb-associated inocula, with no significant difference among vegetation strata. Spore density differed significantly among strata and was highest in herbaceous rhizospheres, including Imperata cylindrica, Cymbopogon citratus, and Themeda gigantea; Eupatorium odoratum also supported high density among shrubs. Available phosphorus was the only soil property that remained significantly associated with spore density after accounting for vegetation stratum and plant species. Exchangeable potassium and soil organic carbon were positively correlated with spore density but did not remain significantly associated in the adjusted models. Total flavonoids differed strongly among vegetation strata but were not significantly associated with field AMF spore density after adjustment for vegetation stratum and plant species and were not correlated with trap-culture colonization or genus richness. Glomus sensu lato was the most frequently detected taxon. Trap-culture colonization of 70–90% and the positive association between available phosphorus and field spore density suggest that AMF propagule metrics may serve as candidate indicators of belowground condition in long-term tropical quarry restoration.