A BRIEF INTRODUCTION TO FIRE HISTORY RECONSTRUCTION 
AND IMPD DATA (AND METADATA) FILE FORMATS


File location: 
https://www.ncei.noaa.gov/pub/data/paleo/firehistory/impd_data_intro.txt


Contents:
I.   Introduction
II.  Tree-ring based fire histories
III. Charcoal-sediment based fire histories


I. Introduction
Fire history information is provided through two types of proxy data; tree-ring 
based records and sediment based records. These data sources describe fire 
regimes at multiple temporal and spatial scales. Tree-ring data provide 
temporally precise, short-term reconstructions of fire events, usually spanning 
the last 400 years or less. By carefully crossdating and examining the tree 
rings, the exact year and often the season in which the fire occurred can be 
determined. These data offer a high level of spatial resolution in a fire 
reconstruction in that the location of fire-scarred trees identifies the exact 
location of particular fires. Although tree-ring methods extend back to the age 
of the oldest living tree, the records attenuate back through time as older 
trees are less abundant.

Charcoal records from sediments can reconstruct much longer fires histories, 
but with less temporal and spatial precision than tree-ring records. Because 
charcoal particles can be carried aloft to great heights and transported great 
distances, the source of the charcoal may be from distant fires as well as 
local fires. Charcoal accumulation may continue for a few years after a fire 
because of transportation and redeposition of secondary charcoal. This process 
tends to blur the exact age of a fire, even when the charcoal particles are 
directly dated by radiocarbon dating, which itself has a dating precision of 
+/- 5%, and the date reflects when the plant was growing, not when it burned. 
Additionally, the charcoal deposited may represent more than one fire within 
the area, or fires from more than one year. As a result, fire episodes are 
referred to as one or more fires occurring in the time interval of interest, 
rather than individual fires.

The International Multiproxy Paleofire Database (IMPD) is an archive of fire 
history data derived from natural proxies such as tree scars and charcoal and 
sediment records. The IMPD was established to provide a permanent repository 
for high-quality paleofire records from around the world. For access to the 
IMPD visit: https://www.ncei.noaa.gov/products/paleoclimatology/fire-history


II. Tree-ring based fire histories
Fires that injure but do not kill a tree often leave distinctive scars that can 
be used to determine when the fire occurred. 

Additionally, high severity fires may kill all the trees in an area, 
particularly if the dominant species has a low fire resistance. Establishment 
dates of even-age tree stands can, under certain conditions, be used to 
identify the minimum age of the last stand-replacement fire. However, because 
the lag in tree establishment after a fire is highly variable, establishment 
dates represent only an upper limit for the date of the fire, and uncertainties 
in determining tree age at sample height can also reduce the temporal precision 
of derived fire dates. Most studies using age structure as a proxy for fire 
combine it with other lines of evidence to determine the timing of fire

Online Resources:
A. Details of Tree-Ring Fire Event data and metadata file naming conventions 
 and formats are located at:
 https://www.ncei.noaa.gov/pub/data/paleo/firehistory/tree_event_info.txt
B. Open Access software programs are available to create, read and use 
 Fire History Exchange Format (FHX) files at:
 https://www.ncei.noaa.gov/pub/data/paleo/firehistory/tree_event_software.txt
C. A sample Fire History Exchange Format (FHX) file is located at:
 https://www.ncei.noaa.gov/pub/data/paleo/firehistory/fire_scar_sample
D. A list of the Fire History Exchange Format (FHX) codes is available at:
 https://www.ncei.noaa.gov/pub/data/paleo/firehistory/fhx2_codes.txt


III. Charcoal-sediment based fire histories
Charcoal is produced when a fire incompletely combusts plant matter. Charcoal 
analysis quantifies the accumulation of charred particles in sediments during and 
following a fire event. Stratigraphic levels with abundant charcoal (so-called 
charcoal peaks) are inferred to be evidence of past fires. These peaks must be 
distinguished from background charcoal in the stratigraphic record, which may be 
introduced through secondary processes such as erosion. The size of the charcoal 
particles can provide clues to the location of fires, since smaller particles are 
apt to travel further. But any interpretations of fire location, size, and 
intensity requires an understanding of the processes that influence charcoal 
production, transport, and deposition. Annually laminated (i.e., varved) sediment 
permits the age of a fire episode to be established to the year, while in 
non-laminated sediment records, the age of a fire event is established by 
interpolation from a series of radiometric ages determined by 210Pb and/or 
radiocarbon dating. 

Online Resources:
A. Details of Charcoal Sediment data and metadata file naming conventions and 
 formats are locate at:
 https://www.ncei.noaa.gov/pub/data/paleo/firehistory/charcoal_sediment_info.txt