Linking sediment‐charcoal records and ecological modeling to understand causes of fire‐regime change in boreal forests

• Published in: Ecology
• Main Authors: Brubaker, Linda B., Higuera, Philip E., Rupp, T. Scott, Olson, Mark A., Anderson, Patricia M., Hu, Feng Sheng
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Ecology, Evolution, Behavior and Systematics; Brooks Range; Alaska
• Online Access: http://dx.doi.org/10.1890/08-0797.1; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2F08-0797.1; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/08-0797.1

Interactions between vegetation and fire have the potential to overshadow direct effects of climate change on fire regimes in boreal forests of North America. We develop methods to compare sediment‐charcoal records with fire regimes simulated by an ecological model, ALFRESCO (Alaskan Frame‐based Ecosystem Code) and apply these methods to evaluate potential causes of a mid‐Holocene fire‐regime shift in boreal forests of the south‐central Brooks Range, Alaska, USA. Fire‐return intervals (FRIs, number of years between fires) are estimated over the past 7000 calibrated 14 C years (7–0 kyr BP [before present]) from short‐term variations in charcoal accumulation rates (CHARs) at three lakes, and an index of area burned is inferred from long‐term CHARs at these sites. ALFRESCO simulations of FRIs and annual area burned are based on prescribed vegetation and climate for 7–5 kyr BP and 5–0 kyr BP, inferred from pollen and stomata records and qualitative paleoclimate proxies. Two sets of experiments examine potential causes of increased burning between 7–5 and 5–0 kyr BP. (1) Static‐vegetation scenarios: white spruce dominates with static mean temperature and total precipitation of the growing season for 7–0 kyr BP or with decreased temperature and/or increased precipitation for 5–0 kyr BP. (2) Changed‐vegetation scenarios: black spruce dominates 5–0 kyr BP, with static temperature and precipitation or decreased temperature and/or increased precipitation. Median FRIs decreased between 7–5 and 5–0 kyr BP in empirical data and changed‐vegetation scenarios but remained relatively constant in static‐vegetation scenarios. Median empirical and simulated FRIs are not statistically different for 7–5 kyr BP and for two changed‐vegetation scenarios (temperature decrease, precipitation increase) for 5–0 kyr BP. In these scenarios, cooler temperatures or increased precipitation dampened the effect of increased landscape flammability resulting from the increase in black spruce. CHAR records and all changed‐vegetation scenarios ...