The natural world catalogs information in many unseen ways. Gases are trapped in ice hundreds of meters inside of a glacier, pollen particles from extinct plants are buried within ancient lakebed sediments, and prehistoric tree rings tell the tales of drought and bounty. Scientists have learned to access these catalogs and address questions about our planet’s past and future. Like trees, many perennial woody shrubs form growth rings that contain important data about responses to environmental drivers. In Arctic regions, which hold immense carbon stores in the soil, climate warming is causing tall deciduous shrubs to increase in both range and abundance with unclear consequences to carbon storage and ecosystem function. My thesis leverages the data in shrub growth rings to address how changing climate conditions will affect Arctic shrub expansion and how this may in turn affect the tundra they are expanding into. This image of a diamond leaf willow (Salix pulchra) was captured using a slide-scanning microscope at the University of Illinois’ Carl R. Woese Institute for Genomic Biology Core Facilities, a superb resource on campus that greatly expedited the rate at which I was able to complete my project.