Data From: Spatiotemporal synchrony of climate and fire across North America (1750-1880)

After a policy of aggressive fire suppression in most of North America during the 20th century, increasing aridity has driven widespread, synchronous fire occurrence in recent decades. A lack of historical (pre-1880) fire records limits our ability to understand long-term continental fire-climate dynamics. The goal of this study is to use tree-ring reconstructions to determine the relationships between spatio-temporal patterns in historical climate and widespread fire occurrence in North America, and whether they are stable through time. 
We applied regionalization methods to tree-ring reconstructions of historical summer soil moisture and annual fire occurrence to independently identify broad- and fine-scale climate and fire regions based on common inter-annual variability. We then tested whether the regions were stable through time and for spatial correspondence between the climate and fire regions. Last, we used correlation analysis to quantify the strength of the fire-climate associ..., Our study area includes North America between 20°N and 60°N (Figure 1). We used this latitudinal range because outside of this area there are few fire history sites with sufficient data prior to 1880 CE (Margolis et al. 2022). The fire data reconstructed from tree rings are located in forested regions; consequently, our study may not be representative of fire regimes in non-forest vegetation.
We analyzed records of fire occurrence for the period 1750-1880 from NAFSN (Margolis et al. 2022), using tree-level records of the year of fire occurrence from 1,159 sites. The start year of the analysis, 1750, was chosen to optimize the longest possible period with the broadest geographic coverage of sites that were continuously recording fire. Continuously recorded fire data are necessary to prevent biases in the cluster analysis related to decreasing sample depth associated with tree-ring sample decay (Swetnam et al. 1999). The analysis period ended in the year 1880 due to the strong influence o..., , # Data From: Spatiotemporal synchrony of climate and fire across North America (1750-1880)

[https://doi.org/10.5061/dryad.280gb5mxh](https://doi.org/10.5061/dryad.280gb5mxh)

Primary data are the occurrence of wildfire based on tree ring fire scars (NAFSN_Fire-Binary_1750-1880_10pct_2min.csv), derived from the North American Fire Scar Network (NAFSN, Margolis et al. 2022). Soil moisture anomalies (SMz_recon.nc) derived from tree rings were derived using methods from Williams et al. 2022. Also included are equal area hexagons (NAM_hexels.shp) used in analyses and a shapefile of North America (NAM.shp). A basemap is provided from Nasa's BlueMarble dataset. Metadata relating to the fire scar sites used in this analysis (NAFSS_Master_Metadata_eqm.csv) and the entire NAFSN as of 2/1/2024 (NAFSS_Master_Metadata.csv) for recreating figure 1. Code for recreating analyses and figures are also included.

## Description of the data and file structure

Fire scar data represents the binary occ...