Alpine treeline is a valuable indicator of climate change because of its sensitivity to temperature. On Pikes Peak (Southern Rocky Mountains, Colorado), tree density and elevation in the forest-tundra ecotone has increased in the last century, corresponding with a 2°C increase in regional growing-season temperature. The purpose of this study was to provide a detailed analysis of the process of treeline advancement. Spatial clustering within age classes and elevational bands was used to identify harsh environments and track the upper climatic boundary of tree establishment. Overall, clustering (Ripley’s K, p < 0.01, based on boot-strapping) was more prominent at lower elevations and for older cohorts, indicating the upward migration of the climatic boundary. However, the climatic boundary may be advancing more quickly than treeline as the moving edge changed from a clustered to a randomly dispersed distribution over time: from 1868-1940 the moving edge was clearly clustered, from 1941-1976 it showed mixed results, and from 1977-2010 it displayed a random spatial pattern. Treeline advancement also demonstrated a reach-and-fill pattern, with sudden advancement of treeline, followed by a few decades of infill at lower elevations. The reach-and-fill pattern repeated three times in the last 120 years, with exponential increases in tree density, especially in the last 40 years. The recent explosion of growth and the quickly advancing climatic boundary match temporally with a shift from an abrupt to a diffuse edge typology. To my knowledge, this is the first study that examines in detail the process of changing treeline typology of an advancing treeline.
The 2014 legalization of cannabis sales in Colorado led to the promulgation of municipal regulations to mitigate potential negative effects of these newly licensed businesses on their surrounding communities. However, the rhetoric from opponents to legalization efforts has used “negative impacts on residential housing prices” as a primary argument. Of the three classes of regulatory licensing (retail stores, manufacturing facilities and cultivation operations), this study primarily analyzes retail stores in relation to residential housing prices. Though firms within each of these classes have the potential to affect surrounding residential property values in different ways, this study focuses on the retail store effect. Using six years of geo-coded data on home sales in Denver County, I analyze the effects of cannabis businesses on residential property values since legalization. I find that houses sold after the legalization of marijuana sell for a higher transaction price than houses sold before legalization, while closer proximity to marijuana businesses decreases the housing transaction price.