Modeling climate and wildfire mitigation treatment impacts on forest carbon sequestration

Background/Question/Methods

Changing climatic conditions and disturbance represent risks to forest-based carbon sequestration and may result in a positive feedback if disturbance-based emissions are greater than net primary productivity in undisturbed areas.  Quantifying the impacts of altered precipitation and temperature on forest growth rates as a function of atmospheric greenhouse gas concentration can serve to provide insight into the sign and strength of this feedback.  We used a climate-sensitive growth-and-yield model to quantify the effects of altered climate on mixed-conifer forest growth under both low and high emissions scenarios from four downscaled general circulation models in the Lake Tahoe Basin, California.  Climate scenarios were also coupled with a range of wildfire risk mitigation strategies to determine the impacts of these treatments on carbon sequestration as a function of climate.  We compared mid- and late-century carbon stocks with a baseline period of 1970-1999.

Results/Conclusions

Recursive partitioning analysis indicated that the factors that most influenced growth were general circulation model, forest composition, and simulation period.   Comparison with the late 20^th century baseline period showed a consistent reduction in growth for most scenarios.  Deviation in growth as compared with the baseline period was most prevalent at the end of the 21^st century under a high (A2) emission scenario, where average forest growth slowed twice as much as the more optimistic low (B1) emission scenario.  The results were mixed across treatments.  These results suggest that the sink strength of forests in the Lake Tahoe Basin may weaken considerably by the end of the 21^st century.