The role of semi-arid ecosystems in the global carbon cycle

Much of my past research has shown that semi-arid ecosystems are not well represented in land surface/terrestrial biosphere models. This is crucial, given these ecosystems are in transition zones that are vulnerable to climate change and land degradation.

I am currently investigating the cause of terrestrial ecosystem model-data discrepancy in dryland (grassland, shrubland, and semi-arid desert) vegetation and carbon dynamics in close association with ecohydrologists at the USDA and principal investigators of ~20 Ameriflux eddy covariance flux tower sites across the southwest US. We aim to better understand the impact of moisture availability on coupled carbon, water, and vegetation dynamics, and to ensure these processes are improved in models.

Based on our analysis, terrestrial models included in the last IPCC Coupled Model Inter-comparison Project (CMIP5) underestimated annual net CO2 exchange in the SW US due to a poor representation of moisture controls on vegetation during periods of water limitation; therefore, the role of semi-arid ecosystems in the global carbon inter-annual variability and trend may be more important than previously thought.

In addition to this modeling work, and as part of this wider research goal, we have also published a paper examining how well different satellite products capture seasonal vegetation dynamics in the semi-arid southwestern US: