Insights about Stomatal Behavior and Surface Conductance from Globally Distributed Ecosystem Scale Observations (FLUXNET)

Abstract:

Surface conductance acts as a key linkage between terrestrial water and carbon balances and strongly influences land surface response to and feedback on the near surface environment (temperature and humidity). Theory suggests optimal stomatal behavior that maximizes carbon gain while minimizing water loss. This is often examined by analysis of Water Use Efficiency (CO₂ uptake / H₂O loss) from observations of assimilation and transpiration, though is more formally tested with examination of the marginal water cost of plant carbon gain (dE/dA). Plant species and forms are known to vary in their water use habits, with some forms being relatively conservative (e.g trees) and others exhibiting more profligate behavior (e.g. grasses, crops), likely relating to plant hydraulics. Under drought conditions such relations remain little studied though one might expect profligate users to transition toward a more conservative strategy. Globally-distributed observations of ecosystem scale water and carbon fluxes and associated environmental conditions from FLUXNET provide an emerging opportunity to examine the above relationships and theory in hopes of improving ability to characterize surface conductance. This presentation will seek to review recent findings and offer new analysis and synthesis perspectives on plant water use strategies and carbon gain with implications for energy balance, runoff, the Budyko hypothesis.