Root endophyte colonization in the black sand extended growing season experiment for Audubon, Lefty, East Knoll and Trough sites, 2023.

This dataset contains detailed microscopy-based observations of root colonization by three major fungal guilds—arbuscular mycorrhizal fungi (AMF), dark septate endophytes (DSE), and fine root endophytes (FRE)—across multiple alpine plant species sampled from experimental black sand (early snowmelt) plots in the Rocky Mountains. Root samples were collected from plots subjected to different snowmelt timing treatments ("Early" and "Control") using black sand to cause early snowmelt to investigate the effects of phenological shifts in plants on fungal colonization. Each sample includes metadata on collection date, field location, plant species, and staining/scoring logistics, as well as quantified colonization metrics such as hyphae, arbuscules, vesicles, and other fungal structures. This dataset supports ongoing research into how alpine plant–fungal interactions respond to changing environmental conditions and may help identify shifts in mutualistic and non-mutualistic associations under climate-altered snowmelt regimes.