Human induced climate change is expected to increase temperatures in inter-continental regions of Northern America from 2Àö to 4.5ÀöC. This rapid change alters resource availability and places new stressors on vegetation. In this study I compare plastic avoidance and tolerance responses for two contrasting long-lived forb species (H. quinquenervis and E. speciosus). My experimental site was located in a Colorado subalpine meadow where overhead heaters have warmed vegetation and soil for the past 20 years to mimic expected climate changes. In warmed plots, H. quinquenervis has increased in abundance, size and flowering rate while E. speciosus has decreased in these parameters. Therefore, I expected to observe more tolerance responses in H. quinquenervis than in E. speciosus. To test this hypothesis I assessed photosynthetic CO2 assimilation rates, biochemical photosynthetic limitations and water use efficiency (WUE). Relative to control plots, CO2 assimilation rates were lower in heated plots for both species. However, there were no differences in the photosynthetic limitations derived from these A/Ci curves for treatment, species or their interaction. Lack of significance in these parameters is possibly related to the small sample size. WUE, or carbon gained per unit of water lost, had significantly greater values for E. speciosus than for H. quinquenervis. The ability of H. quinquenervis to maintain low WUE rates under potential water stress may be associated with its root structure as well as its ability to respond through tolerance mechanisms. This study reveals the importance of different stress responses as they relate to species success in a changing climate. By understanding the mechanisms behind differential species success, we can better predict and mitigate future climate changes.