Testing simple new conductance models that are derived from a process model and can be parameterised by gas exchange

Background/Question/Methods

Representation of stomatal physiology in models of plant-atmosphere gas exchange is minimal, and direct application of process-based models is limited by difficulty of parameter estimation.  We derived simple models of stomatal conductance from a recent process-based model, and cross-validated them against measurements of sap flux in mature and post-fire regrowth stands of Eucalyptus delegatensis and E. pauciflorain the mountains of southeastern Australia. 

Results/Conclusions

The derived models – which are driven by irradiance and evaporative demand and have 2-4 parameters that represent sums and products of biophysical parameters in the process model – reproduced a median 83-89% of observed variance in half-hourly and diurnally averaged sap flux, and performed similarly whether fitted using a random sample of all data or using one month of data from spring or autumn.  Our simple models are an advance in predicting plant water use because their parameters – which can be estimated by gas exchange – are transparently related to reduced processes and properties, enabling easy accommodation of improved knowledge about how those parameters respond to environmental change and differ among species.