The 65 ha Big Windy Hot Springs Research Natural Area (RNA) in the Steese National Conservation Area of central Alaska is managed by the Bureau of Land Management. It contains a vent that issues hot water at about 61° C flowing at about 8 liters per minute from the largest of a system of small springs and seeps. Geothermal water seeping over the face of a cliff has intensely weathered the local granitic bedrock into gruss. The fracture of massive boulders from the possibly fault-related cliff is one of the most distinctive features of the RNA. Small boulders from the cliff have fallen into Big Windy Creek where they have been caught in the swirling current of Big Windy Creek and ground potholes into the bed of the high-gradient stream. Big Windy Creek is constricted to a narrow canyon. The main geothermal pools are lined with thermophytic algal and cyanobacteria mats. Undescribed high-temperature aquatic species may be present. geothermal heat in the vicinity of the main vents promotes a lush growth of vegetation including Phalaris arundinacea and Ranunculus cymbalaria, two species that occur here north of their previously reported distribution in Alaska. The RNA contains contrasting north- and south-facing canyon slopes. Diffuse geothermal heating of soil around the vents is associated with a large and productive mature white spruce forest on the south-facing slope. A paper birch forest with a minor white spruce component covers most of the south-facing slope. The north-facing slope is underlain with permafrost; areas of boulder talus are subjected to periglacial weathering processes. Low paper birch forest, black spruce woodland, and dwarf birch tundra provide the main vegetation cover. The lowland east-central Alaska region has experienced a strong climate warming trend since the late 1970s. Radial growth of white spruce at Big Windy Hot Springs is generally negatively related to summer temperature. The Big Windy Hot Spring site is a mineral lick heavily used by a local population of Dall sheep that roam from nearby alpine habitats into the RNA. A collection of the water shrew (Sorex palustris) in the RNA is several hundred km from other known populations and is the new northern limit for the species in North America.

This publication is the fourth in the Alaska RNA series, and the first published by the University of Alaska Fairbanks.