Environmental & Climate Sciences Department Seminar

Vegetation acts as a substantial link between the geosphere and atmosphere, mediating transpiration (E), and carbon assimilation (A). At the center of this process lie stomata, small pores which actively regulate the rate of CO2 and H2O diffusion between vegetation and the environment. This process, known as stomatal conductance (gs) helps set the upper limit on E, and through stomatal limitation on A, is a strong determinant of net primary productivity. A series of mathematical models have been developed to predict the sensitivity of gs to environmental factors, which have been incorporated into land surface models (LSMs). Despite the clear importance of accurately representing gs in LSMs, major uncertainty remains in the factors influencing the model parameters related to gs (the stomatal slope and stomatal intercept), particularly in how they are estimated from data, their temporal consistency, and their degree of variation within plant functional types (PFTs). In my talk, I will detail research which has been done to assess these three main sources of stomatal parameter uncertainty. Topics include the impact of branch excision on estimating stomatal parameters, the temporal consistency (diurnal, seasonal, and annual) of stomatal traits, and the model implications of failure to account for Arctic specific stomatal parameters. Overall, I demonstrate the effects of several biotic and abiotic drivers of variation in stomatal parameters, which contribute to significant uncertainty in LSM representation of instantaneous gs and evapotranspiration.