Context: Fire is an important driver of ecological processes in semiarid systems and serves a vital role in shrub-grass interactions. In desert grasslands of the Southwestern US, the loss of fire has been implicated as a primary cause of shrub encroachment. Where fires can currently be re-introduced and managed given past state changes and recent restoration actions, however, is unknown and controversial. We predicted that climate, soil, and topographic variables could be used to predict fire distributions and map the potential for use of fire in management. We also predicted that under conditions of intermediate precipitation, soil-landscape properties would have a significant effect on fire ignition frequencies.

Methods: We characterized the spatial distribution of fire in the Chihuahuan Desert and Madrean Archipelago ecoregions and investigated the influence of soil properties compared to other commonly used biophysical variables using multi-model inference techniques. 

Results: Soil-landscape properties significantly influenced the spatial distribution of fire ignition points. Bottomland ecological sites (i.e., soil-landscape classes) experienced more fires than expected in contrast to ecological sites with coarse soil textures and high fragment content that experienced fewer fire ignitions than expected. Influences of mean annual precipitation, distance to road/rail, soil available water holding capacity and topographic variables varied between ecoregions and by political jurisdictions and differed for peak and nonpeak fire seasons. 

Conclusions: Understanding the spatiotemporal distribution of recent fires in desert grasslands is perhaps the most important factor for predicting future patterns of fire in response to climate change. While climate variables have proven useful for predicting fire patterns in most systems, the use of landscape units such as ecological sites presents an opportunity for incorporating fire-related ecological processes into management planning. The application of soil property information readily available in soil survey for predicting fire size and spatial distribution is an important addition to the toolbox for predicting and managing fire.