Carbon and charcoal in compound disturbance environments
“Black carbon is hard to break down, and formation of this reserve therefore creates a long-term soil carbon sink.”
The 2002 Hinman fire burning (left) and the resultant fire severity (red high, green low)
Field Collections
Several fires are currently being investigators by members of the Buma lab and other collaborators at Colorado College, across the southern Rockies and soon, Alaska. We are investigating not only how compound disturbances influence carbon and charcoal, but how time since fire influences charcoal, carbon, and charcoal fluxes out of watersheds - we are doing this by expanding with aquatic biogeochemistry collaborations and incubations to look at gaseous losses.
Lab Analyses
Intensive lab processing of the soils for both total carbon and charcoal content revealed some interesting differences. Charcoal (a long-lived carbon sequestering material) showed surprising patterns in compound disturbance situations (Buma et al. 2013) and export patterns (gaseous and aquatic) appear similar in ongoing work. Generally, the charcoal is isolated via the KMD digestion, a weak nitric acid method that is well suited for forest soils in higher latitudes.
Image from Flannigan (2015)
There is a lot more to carbon dynamics in multiple disturbance environments than just the first-order, what is left after the burn considerations. Changes in successional trajectories kicked off by the compound event can cause differential C accumulation. Charcoal itself can change microbial respiration rates. Charcoal also changes the albedo of the surface, influencing soil temperature and thus respiration. In the far north, permafrost changes become significant as well. To combine these complex dynamics into a coherent whole, a new NSF program is being initiated with collaborators from around the country to investigate landscape resilience, carbon dynamics, and build a new modeling system to better understand how boreal forests will respond to multiple fires in the future.
The project is a collaborative effort with Portland State University, the University of Alaska, the University of Idaho, and North Carolina State University.
Historically, boreal conifer dominated ecosystems have positive feedbacks, enabling it to retain its' identity despite occasional fires. With multiple, repeat burns, this system may transition to a hardwood dominated system or a graminoid dominated system - climate change may exacerbate this effect by altering permafrost and drainage, which then feedback into fire severity (blue arrows transitioning to red arrows - smaller stability domains.).
Integration of empirical data into simulation modeling (red arrows), with new model linkages for permafrost thawing (blue arrows). This approach will be used to determine how single and multiple burns affect the spatial and temporal pattern of C stocks and fluxes, and the successional dynamics and how subsequent changes in climate change, including permafrost thaw, may alter those trends (grey arrows).
