The authors found that all of the treated stands had lower fire severity and reduced crown scorch than the untreated plots.

The authors found that lightning activity and lightning-started fires are likely to increase in a warmer climate. They found a 44% increase in the likelihood of lightning-caused fires for a 2 X CO2 climate scenario.

The authors found a significant shift in both an earlier beginning and a later end to the fire season for the 2 X CO2 scenario across all regions. They predicted an increase of the fire season of almost 30 days on average. The authors further mention that this would result in a longer period of increased temperatures during the fire season, and therefore, an increase in fire activity across the region.

The authors found that fire was frequent with median intervals of less than 15 years in the Jeffrey pine-mixed conifer forests. However, a period of reduced fire occurrence from the 1790s to 1830s coincided with a similar fire-free period across the Southwest and southern South America. The authors and others found a reduction in the amplitude of ENSO during this time that likely contributed to this reduction in fire occurrence. However, an increase in livestock grazing intensity and a reduction of fire use by native peoples occurred at the same time and likely also had strong influences on the fire regime during this period.

Increased tree densities and a shift toward fire-intolerant white fir in the understory due to fire suppression have impacted the timing of and the response of forest stands to infestations to some degree. The authors explain that white fir is more susceptible to mortality from spruce budworm, and increased mortality can lead to increased fire intensity. Regional outbreaks of spruce budworm were directly related to spring precipitation amount.

Environmental drivers of weather and climate, interacting with landform, set the overall template for individual fire events and fire regimes. Interactions between fire spread and vegetation determine the properties of fires at fine scales, while creating broad-scale landscape pattern.

The authors found that current and projected conditions in the structure and composition of ponderosa pine forests are approximately 97% departed from reference conditions on the Kaibab Plateau. Conditions in these forests are likely to persist due to the continued fire suppression and lack of management activities to reduce forest density.

The authors found that most, but not all, large fires occurred during the La Niña phase of ENSO. For the Cerro Grande fire, which occurred during an extreme La Niña event, topography had a stronger influence on reducing severity in some areas than the regional effects of climate. Conversely, on several of the fires, topography conducive to fire spread did not produce increased severity, and temperature and wind had a stronger influence on fire effects.

Fires prior to 1763 were synchronous with region-wide fire years, which coincided with periods of drought. However, after 1763, fires on the peak became asynchronous to widespread-fire years throughout the region. The authors suggest that when this occurs, bottom-up factors may have become more important in controlling the spread of fire. Specifically, Rincon Peak is isolated and surrounded by talus slopes and rock outcrops. However, they also hypothesized that a variation on ENSO, the late 18th-- early 19th century transition period (LEENT) may have occurred at this time, lengthening the fire-free interval. The LEENT period decreased the ENSO signal and limited the wet/dry oscillations and therefore the cycles of high fuel production followed by drought, hence increased flammability, for an extended period. The author’s findings suggest that isolated sky island ponderosa pine forests may be especially susceptible to climate change and drought because of their separation from the larger landscape and the frequent fire regimes that regulate severity in these ecosystems.

Although they vary widely across regional and temporal gradients, throughout the West moisture anomalies from two years up to the spring proceeding the fire season are widely linked to fire activity.