The dynamics of gas exchange between vegetation and the atmosphere is determined by both physiological controls and environmental conditions. Climate change is predicted to regionally alter several environmental conditions including air temperature, humidity, and soil moisture, all of which directly impact the timing and magnitude of gas exchange in vegetation. Much is known about how vegetation responds to changes in each of these variables, however, little is known about how vegetation will respond to possible interactions between shifts in both temperature and precipitation.  The Boston Area Climate Experiment in Waltham, MA was established to investigate changes in plant and soil dynamics over a response surface, as opposed to testing responses to single step increases in temperature and precipitation.  We investigated shifts in photosynthesis and transpiration rates of a widely distributed ‘old field’ plant, the common dandelion (Taraxacum officinale), under 12 different temperature and precipitation regimes at the Boston Area Climate Experiment.  Gas exchange was measured at different points over the growing season using a LiCOR 6400. 

Results/Conclusions

We found no significant individual effects of temperature or precipitation on plant photosynthesis or transpiration, but we found a strong interaction effect of temperature and precipitation on transpiration rates.  These results indicate the importance of considering both temperature and precipitation changes when measuring the impacts of climate change on plant communities.