A central question in ecology and global change studies asks: how do organisms and ecosystems react to climatic change? To assess subalpine plant responses to increases in temperature over both the long and short term, we examined variation in leaf functional traits across a natural elevation gradient and in an experimental warming treatment at the Rocky Mountain Biological Laboratory in Gothic, Colorado. Plant traits studied were leaf maximum assimilation rate of carbon dioxide (A_max) and Specific Leaf Area (SLA). These traits were measured in seven herbaceous and shrubby species commonly found along the elevational gradient. Of these species, six showed a higher SLA with increased elevation (and thus decreasing temperature), while no species showed significant trends for A_max. In response to short term heating, no differences in SLA or A_max were found for most species. Only two species responded to heating: Erigeron speciosus and Eriogonum subalpinum. Erigeron speciosus was found to have higher SLA values in control plots while Eriogonum subalpinum had a higher A_max in control plots. We conclude that the relatively short termed experimental warming has a small effect on plant leaf functional traits, but natural warming along an elevation gradient shows more variation. We also found that species’ potential ranges play an important role in the response to temperature. The time period in which adaptation, acclimatization and acclimation take place is likely the determining factor that controls plant response in a given area. Our results suggest further investigation of these traits and acceptance of plant response as an integral part of global climate change science.