Short answers, pulled from the story.
A fire regime is the pattern, frequency, and intensity of bushfires and wildfires that prevail in an area over long periods of time. It is an integral part of fire ecology and describes the spatial and temporal patterns of fire on the landscape, along with fire's ecosystem impacts.
If fires occur too frequently, plants may be killed before they mature or produce enough seed to ensure population recovery. If fires are too infrequent, plants may mature, weaken, and die without ever releasing their seed, cutting off reproduction entirely.
According to a study by Hardesty and colleagues assessing a subset of the WWF's Global 200 ecoregions, 84 percent were at risk from altered fire regimes. Only 16 percent of the assessed land area had fire regimes consistent with ecosystem health.
Bromus tectorum, or cheatgrass, reduced the historical fire return interval in the Snake River Plain sagebrush from 60-110 years down to approximately every 5 years. It acts as a continuous fuel source, creating a cycle too rapid for native vegetation to fully recover.
Climate change is projected to increase fire frequencies, lengthen fire seasons, and raise the annual number of extreme fire weather days. A study in southeast Australia found that prolonged wildfire seasons burned 87 percent of the mountain ash species range, with subsequent re-burns causing complete regeneration failure and conversion of forest to shrubs and grasslands.
Researchers use fire scar analysis on trees, age distributions of forest stands, charcoal samples, and long-term vegetation changes to identify past fire events. These methods can extend the record of fire-climate interactions by thousands of years, far beyond what historical fire records alone can provide.