Impacts of changing drought deciduous phenology in the Community Land Model

Background/Question/Methods

Drought deciduous plants are highly sensitive to climate and weather and may already be changing their seasonal cycles due to warming, changes in precipitation patterns, and/or CO₂ fertilization. These shifts in phenology, could have large impacts on the global carbon cycle, water balance, albedo, and on the humans and other animals that depend on these regions. From an earth system perspective these impacts may then feed back into the climate system and impact how, when, and where climate change occurs.

Here we compare 29 years of monthly leaf area index (LAI) outputs from the Community Land Model (CLM), the land component of the Community Earth System Model, to LAI derived from the AVHRR NDVI3g product (LAI3g). After making a change to the CLM to improve its ability to predict phenological cycles in semi-arid regions, we consider the impacts of this change on ecosystem productivity, the fire cycle, and climate.

Results/Conclusions

We found that changing the CLM drought deciduous phenology algorithm improved the model’s ability to match the seasonal cycle in the LAI3g dataset, particularly in regions dominated by tropical deciduous trees. This change led to shifts in the fire cycle in the model and to improvements in overall predictions of gross primary productivity.  Future work will include running a coupled version of the model (CESM) to test the impacts of these changes to the global climate.